EP3384534A1 - Optoelectronic device comprising three-dimensional semiconductor structures with a wider single-crystal portion - Google Patents

Optoelectronic device comprising three-dimensional semiconductor structures with a wider single-crystal portion

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Publication number
EP3384534A1
EP3384534A1 EP16813091.2A EP16813091A EP3384534A1 EP 3384534 A1 EP3384534 A1 EP 3384534A1 EP 16813091 A EP16813091 A EP 16813091A EP 3384534 A1 EP3384534 A1 EP 3384534A1
Authority
EP
European Patent Office
Prior art keywords
optoelectronic device
doped
doped portion
semiconductor compound
enlarged
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP16813091.2A
Other languages
German (de)
French (fr)
Inventor
Pierre Ferret
Abdelkarim KAHOULI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Application filed by Commissariat a lEnergie Atomique CEA, Commissariat a lEnergie Atomique et aux Energies Alternatives CEA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP3384534A1 publication Critical patent/EP3384534A1/en
Withdrawn legal-status Critical Current

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    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/20—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
    • H01L33/24—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate of the light emitting region, e.g. non-planar junction
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    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035209—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures
    • H01L31/035227—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures the quantum structure being quantum wires, or nanorods
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    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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    • H01L31/0264—Inorganic materials
    • H01L31/0304—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds
    • H01L31/03044—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds comprising a nitride compounds, e.g. GaN
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    • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/0304—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds
    • H01L31/03046—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds including ternary or quaternary compounds, e.g. GaAlAs, InGaAs, InGaAsP
    • H01L31/03048—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds including ternary or quaternary compounds, e.g. GaAlAs, InGaAs, InGaAsP comprising a nitride compounds, e.g. InGaN
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    • H01L31/035236—Superlattices; Multiple quantum well structures
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    • H01L31/035281—Shape of the body
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    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1844—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising ternary or quaternary compounds, e.g. Ga Al As, In Ga As P
    • H01L31/1848—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising ternary or quaternary compounds, e.g. Ga Al As, In Ga As P comprising nitride compounds, e.g. InGaN, InGaAlN
    • H—ELECTRICITY
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    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1852—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising a growth substrate not being an AIIIBV compound
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    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
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    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • H—ELECTRICITY
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    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of group III and group V of the periodic system
    • H01L33/32—Materials of the light emitting region containing only elements of group III and group V of the periodic system containing nitrogen
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    • H01L33/0004—Devices characterised by their operation
    • H01L33/002—Devices characterised by their operation having heterojunctions or graded gap
    • H01L33/0025—Devices characterised by their operation having heterojunctions or graded gap comprising only AIIIBV compounds

Definitions

  • the field of the invention is that of optoelectronic devices comprising three-dimensional semiconductor structures, such as nanowires or microwires, adapted to emit or detect light radiation.
  • optoelectronic devices comprising three-dimensional semiconductor structures of nanowires or microwires forming, for example, light-emitting diodes.
  • the nanowires or microfilts usually comprise a first doped portion, for example n-type, wire-shaped, and a second doped portion of the opposite conductivity type, for example p-type, between which is located an active zone comprising at least one well quantum.
  • the nanowires or microwires may be made in a so-called axial configuration, in which the active zone and the second p-doped portion extend essentially in the extension of the first doped portion, along a longitudinal axis of epitaxial growth, without surrounding the periphery of the the latter. They can also be made in a so-called radial configuration, also called core / shell, in which the active zone and the second p-doped portion surround one end of the first n-doped portion.
  • Nanowires or microwires in radial configuration may, however, have a mismatch between the semiconductor compound forming the active zone and the one forming the first doped portion. Such mesh clash is likely to result in degradation of the electronic and / or optical properties of the nanowires or microwires.
  • the object of the invention is to remedy at least in part the disadvantages of the prior art.
  • the object of the invention is an optoelectronic device, comprising at least one three-dimensional semiconductor structure extending along a longitudinal axis substantially orthogonal to a plane of a substrate on which it rests, and comprising a first doped portion, extending from the substrate along the axis longitudinal, and made of a first semiconductor compound; an active zone comprising at least one quantum well, and extending from the first doped portion; a second doped portion, at least partially covering the active zone.
  • the active zone comprises an enlarged monocrystalline portion formed of a single crystal of a second semiconductor compound formed of a mixture of the first semiconductor compound and at least one additional element; extending from an upper face of an end of the first doped portion opposite the substrate; and having a mean diameter greater than that of the first doped portion.
  • the active zone is made based on said second semiconductor compound.
  • the active zone is made of one or more semiconductor materials which each comprise at least the same elements as those of the second semiconductor compound. It therefore does not include a layer made of the first semiconductor compound.
  • it consists of at least one semiconductor compound comprising at least the same elements as the first semiconductor compound and at least the additional element.
  • the mesh mismatch in the active zone is limited by the fact that it is made from the same semiconductor compound.
  • the most important mismatch is then transferred to the interface between the first semiconductor compound of the first doped portion and the second semiconductor compound of the single crystal. It is then possible to make an active zone of greater thickness and / or greater atomic proportion of the additional element, while the first doped portion is made of the first semiconductor compound.
  • the second semiconductor compound is InGaN.
  • the active zone may include multiple quantum wells that overlap at least a portion of the enlarged monocrystalline portion.
  • Multiple quantum wells may be formed of alternating barrier layers and quantum well forming layers, said barrier layers and quantum wells being made based on the second semiconductor compound.
  • the barrier layers have a first nonzero value of atomic proportion to said additional element of the second semiconductor compound.
  • the quantum wells have a second atomic proportion value in said additional element greater than the first value.
  • the mismatch between the multiple quantum wells made based on the second semiconductor compound and the first doped portion made in the first semiconductor compound is limited.
  • the second semiconductor compound of the expanded monocrystalline portion may be doped with the same type of conductivity as that of the first doped portion.
  • the first semiconductor compound is gallium nitride and the second semiconductor compound is gallium indium nitride.
  • the first atomic proportion value in said additional element of the barrier layers is between 15% and 23%
  • the second atomic proportion value in said additional element of the quantum wells is between 22% and 30%.
  • the first semiconductor compound is GaN
  • the second semiconductor compound of InGaN it is possible to produce quantum wells whose atomic proportion of indium makes it possible to emit light radiation into the green, c. that is to say, whose emission spectrum has a peak intensity at a wavelength of between 495 nm and 50 nm, for example equal to about 530 nm, while having an improved internal quantum efficiency while the first portion doped is made of GaN.
  • the monocrystal has an atomic proportion to said additional element equal to that of the barrier layer in contact therewith.
  • the mismatch between the single crystal and the barrier layer in contact therewith is limited, the most important mismatch being transferred to the interface between the first semiconductor compound of the first doped portion and the second semiconductor compound. of the single crystal, which limits the mechanical stresses between the single crystal and the barrier layer in contact. It is then possible to make quantum wells of greater thickness and / or greater atomic proportion of the additional element.
  • the enlarged monocrystalline portion may have an average thickness, along the longitudinal axis, greater than 10 nm.
  • the enlarged monocrystalline portion may have an average diameter greater than 110% of the average diameter of the first doped portion.
  • Said quantum well may be made of a semiconductor material based on the second semiconductor compound.
  • the first semiconductor compound may be selected from III-V compounds, II-VI compounds and IV elements or compounds, and preferably is a III-N compound.
  • the second doped portion may be at least partially surrounded by a bias electrode.
  • the expanded monocrystalline portion may form a single quantum well, the second semiconductor compound preferably being unintentionally doped.
  • the enlarged monocrystalline portion may have at least two semi-polar faces of different inclinations with respect to the longitudinal axis, said semi-polar faces being covered by at least one quantum well coated by the second doped portion.
  • the optoelectronic device may comprise at least two polarization electrodes adapted to each polarize a portion of the second doped portion located at one or other of said semi-polar faces.
  • the invention also relates to a method for producing an optoelectronic device according to any one of the preceding features, wherein the three-dimensional semiconductor structure is formed by chemical vapor deposition, the first semiconductor compound being a III-V compound.
  • a V / III ratio between a precursor gas stream of element V on a precursor gas stream of element III has a value less than or equal to 100, and wherein during the formation of the expanded monocrystalline portion, said V / III ratio has a value greater than or equal to 500.
  • an H 2 / N 2 ratio between a proportion of molar flow of hydrogen over a proportion of molar flow of nitrogen has a value greater than or equal to 60/40, preferably greater than or equal to 60/40. or equal to 70/30, and wherein during formation of the expanded single crystal portion, said H2 / N2 ratio has a value less than or equal to 40/60, preferably less than or equal to 30/70.
  • FIG. 1 is a partial and schematic cross-sectional view of an example of an optoelectronic device comprising nanowires or microwires in a radial configuration
  • FIG. 2 is a partial schematic cross-sectional view of a first embodiment of an optoelectronic device comprising nanowires or microfilts in a radial configuration and whose active zone comprises an enlarged monocrystalline portion surrounded by multiple quantum wells; ;
  • FIG. 3 is a partial diagrammatic cross-sectional view of the optoelectronic device shown in FIG. 2, illustrating the angles of inclination a and ⁇ respectively formed by the lateral and upper edges with respect to the longitudinal axis. ⁇ of the wire;
  • FIG. 4 is a partial and schematic cross-sectional view of a variant of the first embodiment of an optoelectronic device
  • FIG. 5 is a partial and schematic cross-sectional view of a second embodiment of an optoelectronic device comprising nanowires or microfilts in radial configuration and whose active zone comprises an enlarged monocrystalline portion forming a single quantum well;
  • FIGS. 6 and 7 are partial and schematic cross-sectional views of two variants of the optoelectronic device according to the first embodiment in which the second polarization electrode or electrodes are arranged to polarize different parts of the second doped portion resting on semipolar faces of the wires.
  • the invention relates to an optoelectronic device comprising three-dimensional semiconductor structures adapted to form light-emitting diodes or photodiodes.
  • the three-dimensional semiconducting structures have an elongated shape along a longitudinal axis ⁇ , that is to say whose longitudinal dimension along the longitudinal axis ⁇ is greater than the transverse dimensions.
  • the three-dimensional structures are then called "son", “nanowires” or “microfilts".
  • the transverse dimensions of the wires that is to say their dimensions in a plane orthogonal to the longitudinal axis ⁇ , may be between 1 ⁇ m and 1 ⁇ m, for example between 1 ⁇ m and 10 ⁇ m, and preferably between 100 nm and 5 ⁇ .
  • the height of the wires that is to say their longitudinal dimension along the longitudinal axis ⁇ , is greater than the transverse dimensions, for example 2 times, 5 times and preferably at least 10 times greater.
  • the cross section of the son in a plane orthogonal to the longitudinal axis ⁇ , may have different shapes, for example a circular shape, oval, polygonal for example triangular, square, rectangular or hexagonal.
  • the diameter is defined here as a quantity associated with the perimeter of the wire at a cross-section. It can be the diameter of a disc having the same surface as the cross section of the wire.
  • the local diameter is the diameter of the wire at a given height thereof along the longitudinal axis ⁇ .
  • the average diameter is the average, for example arithmetic, of local diameters along the wire or a portion thereof.
  • FIG. 1 schematically illustrates a partial sectional view of an example of an optoelectronic device 1 comprising three-dimensional semiconductor structures 2 forming wire electroluminescent diodes in a radial configuration.
  • a three-dimensional orthonormal reference ( ⁇ , ⁇ , ⁇ ) is defined here and for the rest of the description, in which the plane (X, Y) is substantially parallel to the plane of a substrate of the optoelectronic device, the Z axis being oriented according to a direction substantially orthogonal to the plane of the substrate.
  • a first portion 10, doped with a first type of conductivity is in the form of a wire which extends along a longitudinal axis ⁇ , the latter being oriented substantially orthogonal to the plane (X , Y) of a front face 3b of a substrate 3.
  • the end 11 of the first doped portion 10, opposite the substrate 3, is covered, at its upper edge 14 and its lateral edge 13, by a layer or stack of layers forming an active zone 30 which comprises at least one quantum well.
  • the active zone 30 is itself covered by a layer forming a second portion 20, doped with a second type of conductivity opposite to the first type.
  • the first doped portion 10 and the second doped portion 20 respectively form the core and the shell of the wire 2 said core / shell configuration.
  • the wire 2 is made based on a first semiconductor compound, for example GaN.
  • the first and second doped portions 10, 20 may be made of respectively n-type and p-type doped GaNs.
  • the active zone 30 comprises at least one quantum well in the form of a layer located between the first and second doped portions 10, 20, and made of a second semiconductor compound formed of a mixture of the first semiconductor compound and at least one additional element, for example from InGaN, so that its bandgap energy is less than that of the first and second doped portions 10, 20.
  • the quantum well forming layer may be disposed between two barrier layers providing better confinement of the charge carriers.
  • the inventors have demonstrated a drawback then arising from the mismatch between the first semiconductor compound of the first doped portion, here GaN, and the second semiconductor compound of the active zone, here InGaN. Such clash of mesh may result in the appearance of structural defects at the interface between the first and second semiconductor compounds, defects likely to degrade the electronic and / or optical properties of the active zone.
  • the second semiconductor compound increases with a mesh parameter substantially equal to that of the first semiconductor compound but undergoes a deformation of its crystallographic structure which results in the generation of mechanical stresses, in particular in compression or in tension .
  • the stresses experienced by the second semiconductor compound can relax and cause the appearance of structural defects, for example so-called disordered mesh dislocations located at the interface between the first and second semiconductor compounds, thereby causing degradation of the electronic and / or optical properties of the wire.
  • the mismatch between the first and second semiconductor compounds then introduces a constraint in terms of the thickness of the second semiconductor compound, and / or in terms of the atomic proportion of the additional element in the second semiconductor compound.
  • Figures 2 and 3 schematically illustrate a partial sectional view of a first embodiment of an optoelectronic device 1 having three-dimensional semiconductor structures 2 forming wire electroluminescent diodes in radial configuration.
  • the optoelectronic device 1 comprises:
  • a substrate 3 for example made of a semiconductor material, having two faces, said rear 3a and before 3b, opposite to each other; a first polarization electrode 4, here in contact with the rear face 3a of the substrate;
  • nucleation layer 5 made of a material adapted to the epitaxial growth of the three-dimensional semiconducting structures, covering the front face 3b of the substrate;
  • At least one three-dimensional semiconductor structure 2 here in the form of a wire, which extends from the nucleation layer 5 along a longitudinal axis ⁇ oriented substantially orthogonal to the plane (X, Y) of the front face 3b of the substrate 3, the wire 2 comprising a first doped portion 10 in contact with the nucleation layer 5, an active zone 30 and a second doped portion 20;
  • the wire 2 represented here has a radial configuration, or core / shell configuration, insofar as the second doped portion 20 surrounds and covers at least part of the active zone 30, and in particular the lateral edge thereof. It therefore has a configuration that differs from the axial configuration in which the n-doped portion, the active zone and the p-doped portion are stacked one over the other along the longitudinal axis of the wire, without the lateral edge of the zone. active is substantially covered by the p-doped portion.
  • lateral or upper edge is meant a surface of a portion of the wire which extends respectively substantially parallel or orthogonal to the longitudinal axis ⁇ .
  • a lateral border may also be called a radial edge, or lateral flank.
  • An upper border can also be called an axial border.
  • the lateral edges may be inclined when they form a non-zero inclination angle with the longitudinal axis ⁇ .
  • the edge 33 of the active zone 30 is here called inclined insofar as it forms an angle of inclination with respect to the longitudinal axis ⁇ other than 0 °, and in particular strictly greater than 0 ° and strictly less than 90 0 , or strictly less than 0 ° and strictly greater than -90 0 .
  • an upper edge for example here the edge 34 of the active zone 30, is said to be inclined when it forms an angle of inclination ⁇ with respect to the longitudinal axis ⁇ other than 90 ° , and in particular strictly greater than 90 ° and strictly less than 180 ° , or strictly less than 90 ° and strictly greater than 0 °.
  • the substrate 3 is here a semiconductor structure, for example silicon. It may be monoblock or formed of a stack of layers such as a substrate of the SOI type (acronym for Silicon On Insulator). More broadly, the substrate may be of a material semiconductor, for example silicon, germanium, silicon carbide, or a compound III-V or II-VI. It can also be made of a metallic material or an insulating material. It may comprise a layer of graphene, molybdenum sulphide or selenide (MoS2, MoSe2), or any other equivalent material. In this example, the substrate is made of highly doped n-type monocrystalline silicon.
  • the first polarization electrode 4 is in contact with the substrate 3, here electrically conductive, for example at its rear face 3a. It can be made of aluminum or any other suitable material.
  • the nucleation layer 5 is made of a material that promotes the nucleation and growth of the yarns, for example aluminum nitride (AlN) or aluminum oxide (Al 2 O 3 ), magnesium nitride (MgxN y ), nitride or carbide of a transition metal or any other suitable material.
  • AlN aluminum nitride
  • Al 2 O 3 aluminum oxide
  • MgxN y magnesium nitride
  • nitride or carbide of a transition metal or any other suitable material for example aluminum nitride (AlN) or aluminum oxide (Al 2 O 3 ), magnesium nitride (MgxN y ), nitride or carbide of a transition metal or any other suitable material.
  • the thickness of the nucleation layer may be of the order of a few nanometers or a few tens of nanometers.
  • the nucleation layer is AlN.
  • the first doped portion 10 of the wire rests on the substrate 3 at the level of the nucleation layer 5. It has a wire shape which extends along the longitudinal axis ⁇ , and forms the heart of the wire heart / shell configuration. It has an end 11, opposite to the substrate, delimited longitudinally by a so-called upper face 14.
  • the upper face 14 extends here substantially orthogonal to the longitudinal axis ⁇ but can be inclined with respect to the axis ⁇ , or even be formed of one or more so-called then elementary faces.
  • the first doped portion 10 is made of a first semiconductor compound, which may be chosen from compounds III-V comprising at least one element of column III and at least one element of column V of the periodic table, among the compounds II- VI comprising at least one element of column II and at least one element of column VI, or of elements or compounds IV having at least one element of column IV.
  • III-V compounds may be III-N compounds, such as GaN, InGaN, AlGaN, AlN, InN or AlInGaN, or even compounds comprising an arsenic or phosphorus-type V column element, for example. example AsGa or InP.
  • compounds II-VI can be CdTe, HgTe, CdHgTe, ZnO, ZnMgO, CdZnO or CdZnMgO.
  • elements or compounds IV may be used, such as Si, C, Ge, SiC, SiGe, or GeC.
  • the first portion is doped according to a first type of conductivity.
  • the first doped portion 10 is made of n-type doped GaN, in particular with silicon.
  • the first doped portion 10 here has an average diameter approximately equal to the local diameter.
  • the average diameter of the first doped portion 10 can be between 1 m and ⁇ , for example between soonm and 5 ⁇ , and is here substantially equal to ⁇ .
  • the height of the first doped portion may be between 1oonm and ⁇ , for example between soonm and 5 ⁇ , and here is substantially equal to 5 ⁇ .
  • a dielectric layer 7 here covers the nucleation layer 5 and forms a growth mask allowing the epitaxy of the son from openings opening locally on the nucleation layer, and a second dielectric layer 8 covers the lateral border of the first doped portion 10.
  • the active zone 30 is the portion of the wire 2 at which most of the light radiation of the wire is emitted. It comprises at least one quantum well made of a semiconductor compound having a band gap energy lower than that of the first doped portion 10 and the second doped portion 20. It extends from the end 11 of the first portion doped 10 and more precisely from the upper face 14. As detailed below, the active zone 30 may comprise a single quantum well or multiple quantum wells in the form of layers or boxes interposed between barrier layers.
  • the active zone 30 comprises a so-called widened monocrystalline portion 31 which extends along the longitudinal axis ⁇ from the upper face 14 of the end 11 of the first doped portion 10.
  • the expanded monocrystalline portion 31 is formed of a single crystal of a second semiconductor compound, different from the first semiconductor compound in the sense that it comprises at least one additional element not contained in the first compound.
  • the second compound is thus formed of a mixture of the first compound and at least one additional element.
  • the atomic proportion of the additional element is chosen as a function of the optical and / or electronic properties sought, and in particular of the emission spectrum of the wire.
  • the second compound is preferably InGaN, of general formula In x Ga (i- x ) N, with, for example, an atomic percentage of indium of the order of 18%.
  • the second semiconductor compound of the expanded monocrystalline portion 31 may be unintentionally doped or doped according to the same type of conductivity and possibly at the same doping level as the first doped portion 10.
  • the enlarged monocrystalline portion 31 is formed of a single crystal of the second semiconductor compound, delimited by a base 32 in contact with the upper face 14 of the first doped portion 10, a lateral edge 33 and an upper edge 34.
  • the lateral edges 33 and upper 34 may have semi-polar faces, that is to say faces inclined vis-à-vis the longitudinal axis ⁇ .
  • the monocrystalline portion 31 is said to be enlarged insofar as it has a mean diameter greater than the average diameter of the first doped portion 10. It thus has a mean diameter which may be between 1.1 and 20 times the average diameter of the first doped portion 10, for example between 2 and 10 times the average diameter of the first doped portion 10, and is here substantially equal to 5 ⁇ .
  • the enlarged monocrystalline portion 31 may have an average thickness greater than 1 ⁇ m which is the order of magnitude of the critical thickness of the second semiconductor compound, here InGaN.
  • the local thickness is the thickness of the enlarged monocrystalline portion 31 along a given axis parallel to the longitudinal axis ⁇ from the upper surface of the first doped portion.
  • the average thickness is the average, for example arithmetic, of the local thicknesses.
  • the average thickness may be between 1 ⁇ m and 2 ⁇ , for example between soonm and ⁇ , and is here substantially equal to 5 ⁇ .
  • the active zone 30 comprises at least one quantum well, which here covers at least in part the enlarged monocrystalline portion 31, and in particular its lateral edges 33 and upper 34.
  • the active zone comprises multiple quantum wells 35 presenting in the form of a stack of layers, one or more layers forming quantum wells interposed between two barrier layers.
  • the layers forming the quantum wells, and preferably also the barrier layers, are made of a semiconductor material based on the second semiconductor compound, that is to say having at least the same elements as the second semiconductor compound, here in InGaN . They are preferably made in the same second semiconductor compound, with different mole fractions for the barrier layers and for the quantum wells.
  • the barrier layers can thus be made of In x iGai x iN with an atomic proportion of indium xi of between approximately 15% and 23%, for example equal to approximately 18%, and the layers forming the quantum wells can be produced by In x2 Gai-x 2 N with an atomic proportion of indium x2 of between approximately 22% and 30%, for example equal to approximately 25%, thereby making it possible to obtain an emission wavelength of between 495nm and sôonm about, for example equal to about min.
  • the atomic proportion x2 is greater than the atomic proportion xi.
  • the light-emitting diode is then to emit light radiation in the green, with a good light output insofar as the internal quantum efficiency is improved by the fact that the mesh mismatch between the monocrystalline portion in InGaN and the wells is limited.
  • multiple quantum then same as the first doped portion is made of GaN.
  • the monocrystalline portion of InGaN has an atomic proportion equal to that of the barrier layer which is in contact with it.
  • the second doped portion 20 forms a layer that covers and at least partially surrounds the active zone 30, that is to say here the expanded single crystal portion 31 and the multiple quantum wells. It is made of a d-doped semiconductor compound. a second type of conductivity opposite to the first type.
  • the semiconductor compound may be the first semiconductor compound, namely here GaN, or preferably the second semiconductor compound, namely here InGaN. It may also include one or more additional elements.
  • the second doped portion 20 is made of InGaN, and is p-type doped, in particular with magnesium.
  • the thickness of the second doped portion may be between 20 nm and 500 nm, for example of the order of 150 nm.
  • the second doped portion 20 may comprise an electron-blocking layer (not shown) located at the interface with the active zone 30.
  • the electron-blocking layer can here be formed of a ternary compound III-N, for example example of AlGaN or ⁇ , advantageously doped p. It makes it possible to increase the rate of radiative recombinations within the active zone.
  • the second polarization electrode 6 here covers the second doped portion 20 and is adapted to apply an electrical polarization to the wire 2. It is made of a substantially transparent material vis-à-vis the light radiation emitted by the wire, for example the indium tin oxide (ITO, for Indium Tin Oxide). It has a thickness of a few nanometers to a few tens or hundreds of nanometers.
  • ITO indium tin oxide
  • the wire 2 when a potential difference is applied to the wire 2 in a direct direction via the two polarization electrodes, the wire 2 emits light radiation whose emission spectrum has a peak intensity at a length of wave depending mainly on the composition of the quantum well.
  • the wire in radial configuration, comprises a quantum well active zone comprising an enlarged monocrystalline portion, the latter lying on an upper face of the first doped portion, this upper face thus forming a nucleation seed for the portion expanded monocrystalline.
  • the latter has a substantially relaxed, i.e. unconstrained, crystallographic structure. mesh being substantially identical to the parameter natural mesh of the compound. This is explained by the fact that unlike the wire described with reference to Figure 1, the area for nucleation of the expanded monocrystalline portion is reduced and less than the average diameter of the monocrystalline portion.
  • the expanded monocrystalline portion then has a good crystalline quality, with a limited density of structural defects.
  • the density of structural defects that is to say the number of defects per unit volume, decreases in particular with the increase in the volume of the expanded monocrystalline portion.
  • the structural defects, of the dislocation type are essentially derived from a plastic relaxation of the second semiconductor compound in the nucleation zone from the upper face of the first doped portion, and are not substantially generated by the enlargement. of the enlarged monocrystalline portion.
  • the active zone may comprise at least one quantum well, made of a material based on the second semiconductor compound, and which rests on the enlarged monocrystalline portion or is formed by it.
  • the effects of the mismatch between the first semiconductor compound of the first doped portion and the semiconductor material forming the quantum well (s) are thus limited.
  • the quantum well (s) then have an improved crystalline quality and thus an increased internal quantum yield.
  • the multiple quantum wells cover and surround at least in part the enlarged monocrystalline portion, which makes it possible to obtain a larger emission area.
  • This increased emission surface combined with optimized internal quantum efficiency, also increases the optical performance of the wire, the latter being defined as the ratio of the light flux emitted on the absorbed electrical power.
  • the active area is formed based on the second semiconductor compound, for example based on InGaN
  • the first doped portion is made of the first semiconductor compound, for example GaN. This improves the best quantum efficiency. It is possible to make an active zone of greater thickness and / or to incorporate more additional element of the second semiconductor compound, for example indium in the case of InGaN.
  • the active zone is formed of multiple quantum wells 35 which cover at least a portion of the enlarged monocrystalline portion 31, formed of an alternation of barrier layers having a first non-zero value In xi of indium atomic proportion and of quantum well forming layers having a second value In x2 of indium atomic proportion higher than the first value In xl , it is possible to make an active zone whose value xi is between 15% and 23% and whose value x2 is between 22% and 30%, even though the first doped portion is made of GaN.
  • the diode is able to emit light radiation in the green, with a good light output as far as the internal quantum efficiency is improved.
  • the yarn 2 is made by epitaxial growth by chemical vapor deposition organometallic (MOCVD, for Metal-Organic Chemical Vapor Deposition, in English) and here are made based on GaN.
  • MOCVD chemical vapor deposition organometallic
  • the parameters influencing the epitaxial growth are in particular:
  • the nominal V / III ratio defined as the ratio between the molar flow of elements of column V on the molar flow of elements of column III, that is to say here the N / Ga ratio during the growth of the first doped portion made of GaN, and the ratio N / (Ga + In), during the growth of the expanded monocrystalline portion and the multiple quantum wells, made in InGaN;
  • the ratio H 2 / N 2 defined as the ratio between the proportion of molar flux of H 2 in the carrier gas of H 2 and N 2 , namely ⁇ ⁇ 2 / ( ⁇ 2 + ⁇ 2 ), on the proportion molar flow of N 2, namely ⁇ 2 / ( ⁇ 2 + ⁇ 2) and ⁇ ⁇ 2 ⁇ 2 being respectively the mole ratios of hydrogen and nitrogen stream;
  • the growth temperature T measured here at the substrate.
  • the first doped portion 10 is formed by epitaxial growth from the nucleation layer 5.
  • the epitaxy can be performed from openings formed in a growth mask 7 of a dielectric material, by example of Si 3 N 4 , previously deposited on the nucleation layer 5.
  • the growth temperature is brought to a first value ⁇ , for example between 950 ° C and noo ° C, and especially between 990 ° C and io6o ° C.
  • the nominal V / III ratio here the N / Ga ratio, has a first value (V / III) i of between 10 and approximately 100, for example substantially equal to 30.
  • the elements of group III and of group V come from precursors injected into the epitaxial reactor, for example the trimethylgallium (TMGa) or triethylgallium (TEGa) for gallium, and ammonia (NH 3 ) for nitrogen.
  • the ratio H 2 / N 2 has a first value (H 2 / N 2 ) i greater than or equal to 60/40, preferably greater than or equal to 70/30, or even more, for example substantially equal to 90/10.
  • the pressure can be set at about 8mbar.
  • first doped portion 10 which has the shape of a wire which extends along the longitudinal axis ⁇ .
  • the first semiconductor compound of the first doped portion 10, namely here GaN, is n-doped with silicon.
  • the first doped portion 10 here has a height of approximately 5 ⁇ and an average diameter of ⁇ approximately. It has an upper face 14, opposite the substrate 3 and oriented along the crystallographic axis c, substantially flat. This upper face 14 forms the axial face 14 of the end of the first doped portion, and provides the nucleation surface function for the formation of the enlarged monocrystalline portion.
  • a dielectric layer 8 covering the lateral edge 13 of the first doped portion 10 can be performed simultaneously with the formation of the first doped portion.
  • a precursor of an additional element for example silane (SiH 4 ) in the case of silicon, is injected with the precursors mentioned above, with a ratio of the molar flows of the gallium precursor on the silicon precursor preferably. between about 500 and 5000.
  • a layer 8 of silicon nitride, for example Si 3 N 4 of a thickness of the order of 1 ⁇ m which covers the lateral edge 13 of the first doped portion, here over its entire height.
  • the enlarged monocrystalline portion 31 is formed by epitaxial growth from the upper face 14 of the first doped portion 10.
  • the growth temperature is brought to a second value T 2 lower than the value ⁇ , for example between 700 ° C. and 8oo ° C., here equal to about 750 ° C.
  • T 2 lower than the value ⁇
  • ⁇ for example between 700 ° C. and 8oo ° C.
  • a precursor of the additional element for example trimethylindium
  • TMIn in the case of indium.
  • the nominal V / III ratio has a second value (V / III) 2 greater than the value (V / III), for example between about 500 and 5000, here substantially equal to 1500.
  • the ratio H 2 / N 2 has a second value (H 2 / N 2 ) 2 less than the value (H 2 / N 2 ) i and less than or equal to 40/60, preferably less than or equal to 30/70, or even more, for example substantially equal to 3/97. Furthermore, the pressure can remain unchanged, and the injection of the silicon precursor is previously stopped.
  • a monocrystalline portion 31 of the second semiconductor compound, here of InGaN with an atomic proportion of indium of the order of 18%, is obtained by epitaxial growth. from the upper face 14 of the first doped portion 10.
  • the expanded monocrystalline portion may be unintentionally doped, but is advantageously doped according to the same type of conductivity and preferably at the same doping level as the first doped portion 10, thus limiting the series resistance associated with the portions 10, 31.
  • multiple quantum wells are formed by epitaxial growth from the expanded monocrystalline portion 31, here at the lateral border 33 and the upper border 34.
  • a stack of barrier layers and at least one layer forming a quantum well is formed, said layers being alternated in the direction of epitaxial growth.
  • the layers forming the quantum wells and the barrier layers are advantageously made in a semiconductor compound which comprises the same elements as the second semiconductor compound, namely here InGaN, with different atomic proportions for the quantum well layers and the barrier layers.
  • the barrier layers are made in the second semiconductor compound, here In x Ga (i- x ) N with x equal to about 18 atomic%
  • the quantum well layers are also made in y Ga (i- y ) N, with y greater than x, for example of the order of 25 atomic%, so as to improve the quantum confinement of the charge carriers in the quantum wells.
  • the formation of the barrier layers and quantum well layers can be carried out at a growth temperature value T 3 substantially equal to the value T 2 , namely here 750 ° C.
  • the ratio V / III has a value (V / III) 3 substantially equal to the value (V / III) 2 .
  • the ratio H 2 / N 2 has a value substantially equal to the value (H 2 / N 2 ) 2 during the formation of the barrier layers and has a value substantially lower than the value (H 2 / N 2 ) 2 during the formation of quantum well layers, for example 1/99.
  • the pressure can remain unchanged.
  • InGaN barrier layers with about 18 atomic% indium and InGaN quantum well layers are obtained with about 25 atomic% of indium.
  • the second doped portion 20 is formed by epitaxial growth so as to cover and surround at least part of the active zone 30.
  • the growth temperature can be increased to a fourth value T 4 greater than the value T 3 , for example of the order of 885 ° C.
  • the ratio V / III may be increased to a fourth value (V / III) 4 greater than the value (V / III) 3 , for example of the order of 4000.
  • the ratio H 2 / N 2 is increased to a fourth value (H 2 / N 2 ) 4 greater than the value (H 2 / N 2 ) 2 , for example of the order of 15/85.
  • the pressure can be decreased to a value of the order of 300mbar.
  • a second doped portion 20 is thus obtained, for example p-type doped GaN or InGaN, which continuously covers and surrounds here the active zone 30, that is to say the multiple quantum wells as well as the enlarged monocrystalline portion.
  • the second doped portion 20 thus forms the shell of the core / shell configuration wire.
  • the second polarization electrode 6 may be deposited so as to be in contact with at least a portion of the second doped portion 20.
  • the second electrode 6 is made of an electrically conductive material and transparent to the light radiation emitted by the son.
  • the application of a direct potential difference to the wires by the two polarization electrodes leads to the emission of light radiation whose properties of the emission spectrum depends on the composition of the quantum well or quantum wells. active area.
  • the enlarged monocrystalline portion 31 has semi-polar faces, formed by the lateral 33 and upper 34 edges.
  • the lateral and upper edges form faces inclined vis-à- screws of the longitudinal axis ⁇ and correspond to semi-polar crystalline planes.
  • the inclined lateral edge corresponds to adjacent crystalline planes of the type (3 o -3 -2) inclined at an angle ⁇ of about 20 ° relative to the longitudinal axis ⁇
  • the inclined upper edge corresponds to planes neighboring crystalline type (1 o -1 3) inclined at an angle ⁇ of about 120 0 relative to the longitudinal axis ⁇ .
  • the difference in inclination between the different semi-polar faces 33, 34 leads to the formation of quantum well layers which differ mutually by the thickness and / or the atomic proportion of the elements. Indeed, in the case of a quantum well forming layer made of InGaN, the incorporation rate of indium and / or the thickness of the layer formed is different depending on whether the deposition is carried out on one side more or less inclined vis-à-vis the longitudinal axis ⁇ . This then results in differences in optical properties, including a difference in emission wavelength, between the quantum wells resting on the semi-polar faces. The light radiation emitted by such a wire can then have an expanded emission spectrum when it comes from the quantum wells located on the different semi-polar faces.
  • FIG. 4 schematically illustrates a partial sectional view of a variant of the first embodiment of an optoelectronic device 1 comprising structures 3-dimensional semiconductors 2 forming wired light emitting diodes in radial configuration and with multiple quantum wells.
  • the optoelectronic device 1 differs from that shown in Figure 2 essentially in that the dielectric layer 8 covering the lateral edge 13 of the first doped portion 10 does not extend over the entire height of the latter.
  • the dielectric layer 8 extends from the nucleation layer 5 over a height H x less than the height H 2 of the first doped portion 10.
  • height we mean the longitudinal extent, according to the longitudinal axis ⁇ , of a layer or portion.
  • a so-called upper zone 13I1 of the lateral edge 13 of the first doped portion 10 which extends from the height H x to the height H 2 , is not covered by the dielectric layer 8, and is called free zone.
  • a second enlarged portion 36 may be formed from the lateral edge 13 of the first doped portion 10 at the free zone 13I1.
  • This second enlarged portion 36 is also made of the second semiconductor compound and has a mean diameter greater than the average diameter of the first doped portion.
  • it is covered by the multiple quantum wells 35, the second doped portion 20 and the second polarization electrode 6.
  • This second enlarged portion 36 is formed by epitaxial growth from the free zone 13I1 of the lateral edge 13 of the first doped portion 10, and as such, undergone mechanical stresses related to the mismatch with the first semiconductor compound, in the extent that it has a large nucleation surface with the first doped portion 10. Also, the crystalline quality of the second enlarged portion 36 is less than that of the enlarged monocrystalline portion 31.
  • the wire 2 may not have a dielectric layer 8 covering at least part of the lateral edge 13 of the first doped portion 10.
  • the second enlarged portion 36 can then cover the lateral edge 13 of the first portion doped over substantially the entire height H 2 .
  • the growth mask 7, advantageously dielectric, then provides electrical isolation between the second bias electrode and the conductive substrate.
  • FIG. 5 schematically illustrates a partial cross-sectional view of a second embodiment of an optoelectronic device 1 comprising three-dimensional semiconductor structures 2 forming wire electroluminescent diodes in radial configuration and with a single quantum well.
  • the optoelectronic device 1 differs from that shown in FIG. 2 essentially in that the active zone 30 comprises a single quantum well formed by the enlarged monocrystalline portion 31.
  • the active zone 30 thus comprises a single quantum well made in the second semiconductor compound, here InGaN, formed of the first semiconductor compound, here GaN, in which is incorporated at least one additional element, here indium.
  • the atomic proportion of the elements of the second In x Ga (i- x ) N semiconductor compound is preferably substantially homogeneous within the quantum well, and the second semiconductor compound is preferably unintentionally doped.
  • the single quantum well of InGaN forms a monocrystal 31 which extends from the upper face 14 of the first doped portion 10 and has a mean diameter greater than the average diameter of the first doped portion 10. It comprises a base 32 in contact with the upper face 14 of the first doped portion 10, a lateral edge 33 and an upper edge 34.
  • the lateral edges 33 and upper 34 have in this example semi-polar faces, that is to say, inclined faces vis-à-vis the longitudinal axis ⁇ .
  • the enlarged monocrystalline portion 31 is covered at least in part by the second doped portion 20, which here covers the lateral edge 33 and the upper edge 34.
  • the second doped portion 20 is in contact with the second polarization electrode 6.
  • the expanded monocrystalline portion 31 is made of InGaN with an atomic proportion of indium of the order of 18% making it possible to obtain an emission wavelength centered on 420 nm at 440 nm or even 25% for obtain a transmission wavelength of the order of soonm.
  • the mean diameter of the enlarged monocrystalline portion 31 is of the order of 5 ⁇ and its average thickness is of the order of 5 ⁇ .
  • the expanded monocrystalline portion 31 thus has, by its epitaxy from a reduced nucleation surface, namely the upper face 14 of the first doped portion 10, a good crystalline quality whose density of structural defects decreases with its volume.
  • FIGS. 6 and 7 schematically illustrate partial sectional views of two variants of the polarization of an optoelectronic device 1 comprising three-dimensional semiconductor structures 2 similar to that shown in FIG. 4.
  • the yarns 2 comprise an active zone 30 with an enlarged monocrystalline portion 31 coated at least in part by multiple quantum wells 35, themselves being coated by the second doped portion 20.
  • the expanded monocrystalline portion 31 is formed of a single crystal of the second semiconductor compound, here of InGaN, having semi-polar faces formed by the borders Lateral 33 and higher 34.
  • quantum wells do not have the same optical properties due to differences in thickness and / or atomic proportion of indium, depending on whether they are arranged on the semi-polar face of the upper edge 34 or on the semi-polar face of the lateral edge 33.
  • the wires 2 differ from that shown in FIG. 4 essentially in that the second polarization electrode 6 is no longer in the form of a layer continuously covering the second doped portion 20 , but in the form of a layer arranged to substantially polarize the quantum wells located at the inclined upper edge 34.
  • the optoelectronic device comprises a thick layer 9 of a dielectric material, disposed between the wires 2 to a height such that it covers the first doped portion 10 and the portion of the second doped portion 20 located at the edge
  • the dielectric material is at least partly transparent with respect to the emission spectrum of the wires and has a refractive index chosen so as to allow the light radiation to be extracted from the wires.
  • the dielectric material may be, inter alia, a silicon oxide or an aluminum or silicon nitride.
  • the second polarization electrode 6 On the thick dielectric layer 9 is deposited the second polarization electrode 6, in the form of a layer of a conductive material and transparent vis-à-vis the emission spectrum of the son, this conductive layer covering the portion of the second portion doped 20 located at the inclined upper edge 34.
  • the second doped portion 20 has a portion located at the inclined upper edge 34 which is in contact with the second bias electrode 6, and a portion at the inclined lateral edge 33 which is in contact with the the dielectric thick layer 9.
  • the electrical resistance of this portion 20 is such that the electric field lines are oriented substantially rectilinearly in the thickness. of the second doped portion 20 from the electrode 6, and do not extend substantially in the transverse directions, in the thickness of the portion 20. Also, only the portion of the second doped portion 20 in contact with the 6 is able to be polarized, the portion of the second doped portion located at the inclined lateral edge 33 and which is not in contact with the electrode 6 being substantially not polarized by the electrode 6.
  • the optoelectronic device 1 comprises two second polarization electrodes, called the upper 6h and the lower 6b electrodes, arranged in such a way as to polarize, for the upper electrode 6h, essentially the portion of the second doped portion 20 located at the inclined upper edge 34, and for the electrode lower 6b, essentially the portion of the second doped portion 20 located at the inclined lateral edge 33.
  • the electrode 6b rests on a dielectric layer 9b and the electrode 6h rests on a dielectric layer 9I1.
  • the second upper 6h and lower 6b electrodes are adapted to apply a distinct or identical electrical potential to the two parts of the second doped portion 20, according to the desired properties of the emission spectrum.
  • the two parts of the second doped portion 20 are polarized by one and / or the other upper 6h and lower 6b electrodes, substantially without interference or crosstalk (in English), because of the electrical resistance of the portion 20.
  • the second biasing electrode can be arranged in the form of not a substantially flat layer, but structured layers as illustrated in US8937297.
  • Three-dimensional semiconductor structures adapted to emit light radiation from an electrical signal have been described, thereby forming light-emitting diodes.
  • the structures may be adapted to detect incident light radiation and to respond to an electrical signal thereby forming a photodiode.
  • Applications may be in the field of optoelectronics or photovoltaics.

Abstract

The invention relates to an optoelectronic device (1), comprising at least one microwire or nanowire (2) extending along a longitudinal axis (Δ) substantially orthogonal to a plane of a substrate (3), and comprising: - a first doped portion (10) produced from a first semiconductor compound; - an active zone (30) extending from the first doped portion (10); - a second doped portion (20), at least partially covering the active zone (30); characterised in that the active zone comprises a wider single-crystal portion (31): - formed of a single crystal of a second semiconductor compound made from a mixture of the first semiconductor compound and at least one additional element; - extending from an upper face (14) of one end (11) of the first doped portion (10), and - having a mean diameter greater than that of the first doped portion.

Description

DISPOSITIF OPTOELECTRONIQUE COMPORTANT DES STRUCTURES SEMICONDUCTRICES TRIDIMENSIONNELLES A PORTION MONOCRISTALLINE ELARGIE  OPTOELECTRONIC DEVICE COMPRISING THREE-DIMENSIONAL SEMICONDUCTOR STRUCTURES WITH EXTENDED MONOCRYSTALLINE PORTION
D OMAINE TECHNIQUE TECHNICAL AREA
Le domaine de l'invention est celui des dispositifs optoélectroniques comportant des structures semiconductrices tridimensionnelles, telles que des nanofils ou microfils, adaptées à émettre ou détecter un rayonnement lumineux.  The field of the invention is that of optoelectronic devices comprising three-dimensional semiconductor structures, such as nanowires or microwires, adapted to emit or detect light radiation.
ÉTAT DE LA TECHNIQUE ANTÉRIEURE STATE OF THE PRIOR ART
Il existe des dispositifs optoélectroniques comportant des structures semiconductrices tridimensionnelles de type nanofils ou microfils formant par exemple des diodes électroluminescentes. Les nanofils ou microfils comportent habituellement une première portion dopée, par exemple de type n, de forme filaire, et une seconde portion dopée du type de conductivité opposé, par exemple de type p, entre lesquelles se situe une zone active comportant au moins un puits quantique.  There are optoelectronic devices comprising three-dimensional semiconductor structures of nanowires or microwires forming, for example, light-emitting diodes. The nanowires or microfilts usually comprise a first doped portion, for example n-type, wire-shaped, and a second doped portion of the opposite conductivity type, for example p-type, between which is located an active zone comprising at least one well quantum.
Les nanofils ou microfils peuvent être réalisés dans une configuration dite axiale, dans laquelle la zone active et la seconde portion dopée p s'étendent essentiellement dans le prolongement de la première portion dopée, suivant un axe longitudinal de croissance épitaxiale, sans entourer la périphérie de cette dernière. Ils peuvent également être réalisés dans une configuration dite radiale, également appelée cœur/coquille, dans laquelle la zone active et la seconde portion dopée p entourent une extrémité de la première portion dopée n.  The nanowires or microwires may be made in a so-called axial configuration, in which the active zone and the second p-doped portion extend essentially in the extension of the first doped portion, along a longitudinal axis of epitaxial growth, without surrounding the periphery of the the latter. They can also be made in a so-called radial configuration, also called core / shell, in which the active zone and the second p-doped portion surround one end of the first n-doped portion.
Les nanofils ou microfils en configuration radiale peuvent cependant présenter un désaccord de maille entre le composé semiconducteur formant la zone active et celui formant la première portion dopée. Un tel désaccord de maille est susceptible d'entraîner une dégradation des propriétés électroniques et/ou optiques des nanofils ou microfils.  Nanowires or microwires in radial configuration may, however, have a mismatch between the semiconductor compound forming the active zone and the one forming the first doped portion. Such mesh clash is likely to result in degradation of the electronic and / or optical properties of the nanowires or microwires.
EXPOSÉ DE L'INVENTION STATEMENT OF THE INVENTION
L'invention a pour objectif de remédier au moins en partie aux inconvénients de l'art antérieur. Pour cela, l'objet de l'invention est un dispositif optoélectronique, comportant au moins une structure semiconductrice tridimensionnelle s'étendant suivant un axe longitudinal sensiblement orthogonal à un plan d'un substrat sur lequel elle repose, et comportant une première portion dopée, s'étendant à partir du substrat suivant l'axe longitudinal, et réalisée en un premier composé semiconducteur ; une zone active comportant au moins un puits quantique, et s'étendant à partir de la première portion dopée ; une seconde portion dopée, recouvrant au moins en partie la zone active. The object of the invention is to remedy at least in part the disadvantages of the prior art. For this, the object of the invention is an optoelectronic device, comprising at least one three-dimensional semiconductor structure extending along a longitudinal axis substantially orthogonal to a plane of a substrate on which it rests, and comprising a first doped portion, extending from the substrate along the axis longitudinal, and made of a first semiconductor compound; an active zone comprising at least one quantum well, and extending from the first doped portion; a second doped portion, at least partially covering the active zone.
Selon l'invention, la zone active comporte une portion monocristalline élargie formée d'un monocristal d'un second composé semiconducteur formé d'un mélange du premier composé semiconducteur et d'au moins un élément supplémentaire ; s'étendant à partir d'une face supérieure d'une extrémité de la première portion dopée opposée au substrat ; et présentant un diamètre moyen supérieur à celui de la première portion dopée.  According to the invention, the active zone comprises an enlarged monocrystalline portion formed of a single crystal of a second semiconductor compound formed of a mixture of the first semiconductor compound and at least one additional element; extending from an upper face of an end of the first doped portion opposite the substrate; and having a mean diameter greater than that of the first doped portion.
De plus, la zone active est réalisée à base dudit second composé semiconducteur. Autrement dit, la zone active est réalisée en un ou plusieurs matériaux semiconducteurs qui comportent chacun au moins les mêmes éléments que ceux du second composé semiconducteur. Elle ne comporte donc pas de couche réalisée en le premier composé semiconducteur. De préférence, elle est constituée d'au moins un composé semiconducteur comportant au moins les mêmes éléments que le premier composé semiconducteur et au moins l'élément supplémentaire.  In addition, the active zone is made based on said second semiconductor compound. In other words, the active zone is made of one or more semiconductor materials which each comprise at least the same elements as those of the second semiconductor compound. It therefore does not include a layer made of the first semiconductor compound. Preferably, it consists of at least one semiconductor compound comprising at least the same elements as the first semiconductor compound and at least the additional element.
Ainsi, on limite le désaccord de maille dans la zone active par le fait qu'elle est réalisée à base du même composé semiconducteur. Le désaccord de maille le plus important est alors reporté à l'interface entre le premier composé semiconducteur de la première portion dopée et le second composé semiconducteur du monocristal. Il est alors possible de réaliser une zone active de plus grande épaisseur et/ou à plus grande proportion atomique de l'élément supplémentaire, alors que la première portion dopée est réalisée en le premier composé semiconducteur.  Thus, the mesh mismatch in the active zone is limited by the fact that it is made from the same semiconductor compound. The most important mismatch is then transferred to the interface between the first semiconductor compound of the first doped portion and the second semiconductor compound of the single crystal. It is then possible to make an active zone of greater thickness and / or greater atomic proportion of the additional element, while the first doped portion is made of the first semiconductor compound.
Par mélange, on entend un alliage, et de préférence un alliage ternaire, formé du premier composé semiconducteur, par exemple du GaN, et de l'élément supplémentaire, par exemple de l'indium. Dans cet exemple, le deuxième composé semiconducteur est de l'InGaN.  By mixing is meant an alloy, and preferably a ternary alloy, formed of the first semiconductor compound, for example GaN, and the additional element, for example indium. In this example, the second semiconductor compound is InGaN.
Certains aspects préférés mais non limitatifs de ce dispositif optoélectronique sont les suivants.  Some preferred but non-limiting aspects of this optoelectronic device are as follows.
La zone active peut comporter des puits quantiques multiples qui recouvrent au moins une partie de la portion monocristalline élargie. Les puits quantiques multiples peuvent être formés d'une alternance de couches barrières et de couches formant des puits quantiques, lesdites couches barrières et puits quantiques étant réalisées à base du second composé semiconducteur. Les couches barrières présentent une première valeur non nulle de proportion atomique en ledit élément supplémentaire du second composé semiconducteur. Et les puits quantiques présentent une deuxième valeur de proportion atomique en ledit élément supplémentaire supérieure à la première valeur. The active zone may include multiple quantum wells that overlap at least a portion of the enlarged monocrystalline portion. Multiple quantum wells may be formed of alternating barrier layers and quantum well forming layers, said barrier layers and quantum wells being made based on the second semiconductor compound. The barrier layers have a first nonzero value of atomic proportion to said additional element of the second semiconductor compound. And the quantum wells have a second atomic proportion value in said additional element greater than the first value.
Ainsi, on limite le désaccord de maille entre les puits quantiques multiples réalisés à base du second composé semiconducteur et la première portion dopée réalisée en le premier composé semiconducteur. En limitant le désaccord de maille, il est possible de réaliser des puits quantiques de plus grande épaisseur et/ou à plus grande proportion atomique de l'élément supplémentaire.  Thus, the mismatch between the multiple quantum wells made based on the second semiconductor compound and the first doped portion made in the first semiconductor compound is limited. By limiting the mismatch, it is possible to make quantum wells of greater thickness and / or greater atomic proportion of the additional element.
De préférence, le second composé semiconducteur de la portion monocristalline élargie peut être dopé du même type de conductivité que celui de la première portion dopée. De préférence, le premier composé semiconducteur est du nitrure de gallium et le second composé semiconducteur est du nitrure de gallium et d'indium.  Preferably, the second semiconductor compound of the expanded monocrystalline portion may be doped with the same type of conductivity as that of the first doped portion. Preferably, the first semiconductor compound is gallium nitride and the second semiconductor compound is gallium indium nitride.
De préférence, la première valeur de proportion atomique en ledit élément supplémentaire des couches barrières est comprise entre 15% et 23%, et la deuxième valeur de proportion atomique en ledit élément supplémentaire des puits quantiques est comprise entre 22% et 30%. Ainsi, dans le cas où le premier composé semiconducteur est du GaN et le second composé semiconducteur de l'InGaN, il est possible de réaliser des puits quantiques dont la proportion atomique d'indium permet d'émettre un rayonnement lumineux dans le vert, c'est-à-dire dont le spectre d'émission présente un pic d'intensité à une longueur d'onde comprise entre 495nm et sôonm, par exemple égale à 530nm environ, tout en ayant un rendement quantique interne amélioré alors que la première portion dopée est réalisée en GaN.  Preferably, the first atomic proportion value in said additional element of the barrier layers is between 15% and 23%, and the second atomic proportion value in said additional element of the quantum wells is between 22% and 30%. Thus, in the case where the first semiconductor compound is GaN and the second semiconductor compound of InGaN, it is possible to produce quantum wells whose atomic proportion of indium makes it possible to emit light radiation into the green, c. that is to say, whose emission spectrum has a peak intensity at a wavelength of between 495 nm and 50 nm, for example equal to about 530 nm, while having an improved internal quantum efficiency while the first portion doped is made of GaN.
De préférence, le monocristal présente une proportion atomique en ledit élément supplémentaire égale à celle de la couche barrière en contact avec celui-ci. Ainsi, on limite le désaccord de maille entre le monocristal et la couche barrière en contact avec celui-ci, le désaccord de maille le plus important étant reporté à l'interface entre le premier composé semiconducteur de la première portion dopée et le second composé semiconducteur du monocristal, ce qui permet de limiter les contraintes mécaniques entre le monocristal et la couche barrière en contact. Il est alors possible de réaliser des puits quantiques de plus grande épaisseur et/ou à plus grande proportion atomique de l'élément supplémentaire La portion monocristalline élargie peut présenter une épaisseur moyenne, suivant l'axe longitudinal, supérieure à 10 nm.  Preferably, the monocrystal has an atomic proportion to said additional element equal to that of the barrier layer in contact therewith. Thus, the mismatch between the single crystal and the barrier layer in contact therewith is limited, the most important mismatch being transferred to the interface between the first semiconductor compound of the first doped portion and the second semiconductor compound. of the single crystal, which limits the mechanical stresses between the single crystal and the barrier layer in contact. It is then possible to make quantum wells of greater thickness and / or greater atomic proportion of the additional element. The enlarged monocrystalline portion may have an average thickness, along the longitudinal axis, greater than 10 nm.
La portion monocristalline élargie peut présenter un diamètre moyen supérieur à 110% du diamètre moyen de la première portion dopée.  The enlarged monocrystalline portion may have an average diameter greater than 110% of the average diameter of the first doped portion.
Ledit puits quantique peut être réalisé en un matériau semiconducteur à base du second composé semiconducteur. Le premier composé semiconducteur peut être choisi parmi les composés III-V, les composés II-VI et les éléments ou composés IV, et de préférence est un composé III-N.Said quantum well may be made of a semiconductor material based on the second semiconductor compound. The first semiconductor compound may be selected from III-V compounds, II-VI compounds and IV elements or compounds, and preferably is a III-N compound.
La seconde portion dopée peut être au moins en partie entourée par une électrode de polarisation. The second doped portion may be at least partially surrounded by a bias electrode.
La portion monocristalline élargie peut former un unique puits quantique, le second composé semiconducteur étant de préférence non intentionnellement dopé. The expanded monocrystalline portion may form a single quantum well, the second semiconductor compound preferably being unintentionally doped.
La portion monocristalline élargie peut présenter au moins deux faces semi-polaires d'inclinaisons différentes par rapport à l'axe longitudinal, lesdites faces semi-polaires étant recouvertes par au moins un puits quantique revêtu par la seconde portion dopée.  The enlarged monocrystalline portion may have at least two semi-polar faces of different inclinations with respect to the longitudinal axis, said semi-polar faces being covered by at least one quantum well coated by the second doped portion.
Le dispositif optoélectronique peut comporter au moins deux électrodes de polarisation adaptées à polariser chacune une partie de la seconde portion dopée située au niveau de l'une ou l'autre desdites faces semi-polaires. The optoelectronic device may comprise at least two polarization electrodes adapted to each polarize a portion of the second doped portion located at one or other of said semi-polar faces.
L'invention porte également sur un procédé de réalisation d'un dispositif optoélectronique selon l'une quelconque des caractéristiques précédentes, dans lequel la structure semiconductrice tridimensionnelle est formée par dépôt chimique en phase vapeur, le premier composé semiconducteur étant un composé III-V.  The invention also relates to a method for producing an optoelectronic device according to any one of the preceding features, wherein the three-dimensional semiconductor structure is formed by chemical vapor deposition, the first semiconductor compound being a III-V compound.
De préférence, lors de la formation de la première portion dopée, un rapport V/III entre un flux du gaz précurseur de l'élément V sur un flux du gaz précurseur de l'élément III présente une valeur inférieure ou égale à 100, et dans lequel lors de la formation de la portion monocristalline élargie, ledit rapport V/III présente une valeur supérieure ou égale à 500. Preferably, during the formation of the first doped portion, a V / III ratio between a precursor gas stream of element V on a precursor gas stream of element III has a value less than or equal to 100, and wherein during the formation of the expanded monocrystalline portion, said V / III ratio has a value greater than or equal to 500.
De préférence, lors de la formation de la première portion dopée, un rapport H2/N2 entre une proportion de flux molaire d'hydrogène sur une proportion de flux molaire d'azote présente une valeur supérieure ou égale à 60/40, de préférence supérieure ou égale à 70/30, et dans lequel lors de la formation de la portion monocristalline élargie, ledit rapport H2/N2 présente une valeur inférieure ou égale à 40/60, de préférence inférieure ou égale à 30/70. Preferably, during the formation of the first doped portion, an H 2 / N 2 ratio between a proportion of molar flow of hydrogen over a proportion of molar flow of nitrogen has a value greater than or equal to 60/40, preferably greater than or equal to 60/40. or equal to 70/30, and wherein during formation of the expanded single crystal portion, said H2 / N2 ratio has a value less than or equal to 40/60, preferably less than or equal to 30/70.
BRÈVE DESCRIPTION DES DESSINS BRIEF DESCRIPTION OF THE DRAWINGS
D'autres aspects, buts, avantages et caractéristiques de l'invention apparaîtront mieux à la lecture de la description détaillée suivante de formes de réalisation préférées de celle-ci, donnée à titre d'exemple non limitatif, et faite en référence aux dessins annexés sur lesquels :  Other aspects, objects, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and with reference to the accompanying drawings. on which ones :
la figure 1 est une vue partielle et schématique, en coupe transversale, d'un exemple de dispositif optoélectronique comportant des nanofils ou microfils en configuration radiale ; la figure 2 est une vue partielle et schématique, en coupe transversale, d'un premier mode de réalisation d'un dispositif optoélectronique comportant des nanofils ou microfils en configuration radiale et dont la zone active comprend une portion monocristalline élargie entourée par des puits quantiques multiples ; FIG. 1 is a partial and schematic cross-sectional view of an example of an optoelectronic device comprising nanowires or microwires in a radial configuration; FIG. 2 is a partial schematic cross-sectional view of a first embodiment of an optoelectronic device comprising nanowires or microfilts in a radial configuration and whose active zone comprises an enlarged monocrystalline portion surrounded by multiple quantum wells; ;
la figure 3 est une vue partielle et schématique, en coupe transversale, du dispositif optoélectronique représenté sur la figure 2, illustrant les angles d'inclinaison a et β que forment respectivement les bordures latérale et supérieure vis-à-vis de l'axe longitudinal Δ du fil ; FIG. 3 is a partial diagrammatic cross-sectional view of the optoelectronic device shown in FIG. 2, illustrating the angles of inclination a and β respectively formed by the lateral and upper edges with respect to the longitudinal axis. Δ of the wire;
la figure 4 est une vue partielle et schématique, en coupe transversale, d'une variante du premier mode de réalisation d'un dispositif optoélectronique ; FIG. 4 is a partial and schematic cross-sectional view of a variant of the first embodiment of an optoelectronic device;
la figure 5 est une vue partielle et schématique, en coupe transversale, d'un second mode de réalisation d'un dispositif optoélectronique comportant des nanofils ou microfils en configuration radiale et dont la zone active comprend une portion monocristalline élargie formant un puits quantique unique ; FIG. 5 is a partial and schematic cross-sectional view of a second embodiment of an optoelectronic device comprising nanowires or microfilts in radial configuration and whose active zone comprises an enlarged monocrystalline portion forming a single quantum well;
les figures 6 et 7 sont des vues partielles et schématiques, en coupe transversale, de deux variantes du dispositif optoélectronique selon le premier mode de réalisation dans lesquelles la ou les secondes électrodes de polarisation sont agencées pour polariser différentes parties de la seconde portion dopée reposant sur des faces semi-polaires des fils. FIGS. 6 and 7 are partial and schematic cross-sectional views of two variants of the optoelectronic device according to the first embodiment in which the second polarization electrode or electrodes are arranged to polarize different parts of the second doped portion resting on semipolar faces of the wires.
EXPOSÉ DÉTAILLÉ DE MODES DE RÉALISATION PARTICULIERS DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
Sur les figures et dans la suite de la description, les mêmes références représentent les éléments identiques ou similaires. De plus, les différents éléments ne sont pas représentés à l'échelle de manière à privilégier la clarté des figures. Par ailleurs, les termes « sensiblement », « approximativement », « environ » s'entendent « à 10% près ».  In the figures and in the remainder of the description, the same references represent identical or similar elements. In addition, the various elements are not represented on the scale so as to favor the clarity of the figures. In addition, the terms "substantially", "approximately", "approximately" are "within 10%".
L'invention porte sur un dispositif optoélectronique comportant des structures semiconductrices tridimensionnelles adaptées à former des diodes électroluminescentes ou des photodiodes. The invention relates to an optoelectronic device comprising three-dimensional semiconductor structures adapted to form light-emitting diodes or photodiodes.
Les structures semiconductrices tridimensionnelles présentent une forme allongée suivant un axe longitudinal Δ, c'est-à-dire dont la dimension longitudinale suivant l'axe longitudinal Δ est supérieure aux dimensions transversales. Les structures tridimensionnelles sont alors appelées « fils », « nanofils » ou « microfils ». Les dimensions transversales des fils, c'est- à-dire leurs dimensions dans un plan orthogonal à l'axe longitudinal Δ, peuvent être comprises entre îonm et ιομηι, par exemple comprises entre îoonm et ιομηι, et de préférence comprises entre 100 nm et 5μηι. La hauteur des fils, c'est-à-dire leur dimension longitudinale suivant l'axe longitudinal Δ, est supérieure aux dimensions transversales, par exemple 2 fois, 5 fois et de préférence au moins 10 fois supérieure. The three-dimensional semiconducting structures have an elongated shape along a longitudinal axis Δ, that is to say whose longitudinal dimension along the longitudinal axis Δ is greater than the transverse dimensions. The three-dimensional structures are then called "son", "nanowires" or "microfilts". The transverse dimensions of the wires, that is to say their dimensions in a plane orthogonal to the longitudinal axis Δ, may be between 1 μm and 1 μm, for example between 1 μm and 10 μm, and preferably between 100 nm and 5μηι. The height of the wires, that is to say their longitudinal dimension along the longitudinal axis Δ, is greater than the transverse dimensions, for example 2 times, 5 times and preferably at least 10 times greater.
La section droite des fils, dans un plan orthogonal à l'axe longitudinal Δ, peut présenter différentes formes, par exemple une forme circulaire, ovale, polygonale par exemple triangulaire, carrée, rectangulaire voire hexagonale. On définit ici le diamètre comme étant une grandeur associée au périmètre du fil au niveau d'une section droite. Il peut s'agir du diamètre d'un disque présentant la même surface que la section droite du fil. Le diamètre local est le diamètre du fil à une hauteur donnée de celui-ci suivant l'axe longitudinal Δ. Le diamètre moyen est la moyenne, par exemple arithmétique, des diamètres locaux le long du fil ou d'une portion de celui-ci.  The cross section of the son, in a plane orthogonal to the longitudinal axis Δ, may have different shapes, for example a circular shape, oval, polygonal for example triangular, square, rectangular or hexagonal. The diameter is defined here as a quantity associated with the perimeter of the wire at a cross-section. It can be the diameter of a disc having the same surface as the cross section of the wire. The local diameter is the diameter of the wire at a given height thereof along the longitudinal axis Δ. The average diameter is the average, for example arithmetic, of local diameters along the wire or a portion thereof.
La figure 1 illustre schématiquement une vue partielle en coupe d'un exemple de dispositif optoélectronique 1 comportant des structures semiconductrices tridimensionnelles 2 formant des diodes électroluminescentes filaires en configuration radiale. FIG. 1 schematically illustrates a partial sectional view of an example of an optoelectronic device 1 comprising three-dimensional semiconductor structures 2 forming wire electroluminescent diodes in a radial configuration.
On définit ici et pour la suite de la description un repère orthonormé tridimensionnel (Χ,Υ,Ζ), où le plan (X,Y) est sensiblement parallèle au plan d'un substrat du dispositif optoélectronique, l'axe Z étant orienté suivant une direction sensiblement orthogonale au plan du substrat.  A three-dimensional orthonormal reference (Χ, Υ, Ζ) is defined here and for the rest of the description, in which the plane (X, Y) is substantially parallel to the plane of a substrate of the optoelectronic device, the Z axis being oriented according to a direction substantially orthogonal to the plane of the substrate.
Dans cet exemple, une première portion 10, dopée d'un premier type de conductivité, se présente sous la forme d'un fil qui s'étend suivant un axe longitudinal Δ, celui-ci étant orienté de manière sensiblement orthogonale au plan (X,Y) d'une face avant 3b d'un substrat 3. L'extrémité 11 de la première portion dopée 10, opposée au substrat 3, est recouverte, au niveau de sa bordure supérieure 14 et de sa bordure latérale 13, par une couche ou un empilement de couches formant une zone active 30 qui comporte au moins un puits quantique. La zone active 30 est elle-même recouverte par une couche formant une seconde portion 20, dopée d'un second type de conductivité opposé au premier type. La première portion dopée 10 et la seconde portion dopée 20 forment respectivement le cœur et la coquille du fil 2 dit en configuration cœur/coquille. In this example, a first portion 10, doped with a first type of conductivity, is in the form of a wire which extends along a longitudinal axis Δ, the latter being oriented substantially orthogonal to the plane (X , Y) of a front face 3b of a substrate 3. The end 11 of the first doped portion 10, opposite the substrate 3, is covered, at its upper edge 14 and its lateral edge 13, by a layer or stack of layers forming an active zone 30 which comprises at least one quantum well. The active zone 30 is itself covered by a layer forming a second portion 20, doped with a second type of conductivity opposite to the first type. The first doped portion 10 and the second doped portion 20 respectively form the core and the shell of the wire 2 said core / shell configuration.
Le fil 2 est réalisé à base d'un premier composé semiconducteur, par exemple du GaN. Ainsi, les première et seconde portions dopées 10, 20 peuvent être réalisées en GaN dopé respectivement de type n et de type p. La zone active 30 comporte au moins un puits quantique sous forme d'une couche située entre les première et seconde portions dopées 10, 20, et réalisée en un second composé semiconducteur formé d'un mélange du premier composé semiconducteur et d'au moins un élément supplémentaire, par exemple de 1'InGaN, de sorte que son énergie de bande interdite soit inférieure à celles des première et seconde portions dopées 10, 20. La couche formant le puits quantique peut être disposée entre deux couches barrières assurant un meilleur confinement des porteurs de charge.The wire 2 is made based on a first semiconductor compound, for example GaN. Thus, the first and second doped portions 10, 20 may be made of respectively n-type and p-type doped GaNs. The active zone 30 comprises at least one quantum well in the form of a layer located between the first and second doped portions 10, 20, and made of a second semiconductor compound formed of a mixture of the first semiconductor compound and at least one additional element, for example from InGaN, so that its bandgap energy is less than that of the first and second doped portions 10, 20. The quantum well forming layer may be disposed between two barrier layers providing better confinement of the charge carriers.
Les inventeurs ont mis en évidence un inconvénient provenant alors du désaccord de maille entre le premier composé semiconducteur de la première portion dopée, ici le GaN, et le second composé semiconducteur de la zone active, ici l'InGaN. Un tel désaccord de maille peut se traduire par l'apparition de défauts structuraux à l'interface entre les premier et second composés semiconducteurs, défauts susceptibles de dégrader les propriétés électroniques et/ou optiques de la zone active. Le désaccord de maille s'entend comme la différence relative entre le paramètre de maille ac2 du second composé semiconducteur et celui aci du premier composé semiconducteur, et peut s'exprimer par le paramètre Aa/a = (aC2-aci)/aC2. Le second composé semiconducteur croît avec un paramètre de maille sensiblement égal à celui du premier composé semiconducteur mais subit une déformation de sa structure cristallographique qui se traduit par la génération de contraintes mécaniques, notamment en compression ou en tension. A partir d'une épaisseur dite critique, de l'ordre de îonm, les contraintes subies par le second composé semiconducteur peuvent relaxer et provoquer l'apparition de défauts structuraux, par exemple des dislocations dites de désaccord de maille localisées à l'interface entre les premier et second composés semiconducteurs, entraînant alors une dégradation des propriétés électroniques et/ ou optiques du fil. The inventors have demonstrated a drawback then arising from the mismatch between the first semiconductor compound of the first doped portion, here GaN, and the second semiconductor compound of the active zone, here InGaN. Such clash of mesh may result in the appearance of structural defects at the interface between the first and second semiconductor compounds, defects likely to degrade the electronic and / or optical properties of the active zone. The mismatch is understood as the relative difference between the mesh parameter a c2 of the second semiconductor compound and that a c i of the first semiconductor compound, and can be expressed by the parameter Aa / a = (a C 2 -a c i) / a C 2. The second semiconductor compound increases with a mesh parameter substantially equal to that of the first semiconductor compound but undergoes a deformation of its crystallographic structure which results in the generation of mechanical stresses, in particular in compression or in tension . From a so-called critical thickness, of the order of 1 μm, the stresses experienced by the second semiconductor compound can relax and cause the appearance of structural defects, for example so-called disordered mesh dislocations located at the interface between the first and second semiconductor compounds, thereby causing degradation of the electronic and / or optical properties of the wire.
Le désaccord de maille entre les premier et second composés semiconducteurs introduit alors une contrainte en termes d'épaisseur du second composé semiconducteur, et/ou en termes de proportion atomique de l'élément supplémentaire dans le second composé semiconducteur. Ces inconvénients viennent notamment limiter la réalisation de diodes électroluminescentes aptes à émettre à des grandes longueurs d'onde, par exemple dans le vert ou le rouge, ainsi que la réalisation de diodes électroluminescentes à zone active de grande épaisseur.  The mismatch between the first and second semiconductor compounds then introduces a constraint in terms of the thickness of the second semiconductor compound, and / or in terms of the atomic proportion of the additional element in the second semiconductor compound. These drawbacks in particular limit the production of light-emitting diodes capable of emitting at long wavelengths, for example in green or red, as well as the production of electroluminescent diodes with a large active area.
Les figures 2 et 3 illustrent schématiquement une vue partielle en coupe d'un premier mode de réalisation d'un dispositif optoélectronique 1 comportant des structures semiconductrices tridimensionnelles 2 formant des diodes électroluminescentes filaires en configuration radiale. Figures 2 and 3 schematically illustrate a partial sectional view of a first embodiment of an optoelectronic device 1 having three-dimensional semiconductor structures 2 forming wire electroluminescent diodes in radial configuration.
Dans cet exemple, le dispositif optoélectronique 1 comporte :  In this example, the optoelectronic device 1 comprises:
- un substrat 3, par exemple réalisé en un matériau semiconducteur, présentant deux faces, dite arrière 3a et avant 3b, opposées l'une à l'autre ; - une première électrode de polarisation 4, ici en contact avec la face arrière 3a du substrat ; - A substrate 3, for example made of a semiconductor material, having two faces, said rear 3a and before 3b, opposite to each other; a first polarization electrode 4, here in contact with the rear face 3a of the substrate;
- une couche de nucléation 5, réalisée en un matériau adapté à la croissance épitaxiale des structures semiconductrices tridimensionnelles, recouvrant la face avant 3b du substrat ;  a nucleation layer 5, made of a material adapted to the epitaxial growth of the three-dimensional semiconducting structures, covering the front face 3b of the substrate;
- au moins une structure semiconductrice tridimensionnelle 2, ici sous forme d'un fil, qui s'étend à partir de la couche de nucléation 5 suivant un axe longitudinal Δ orienté de manière sensiblement orthogonale au plan (X,Y) de la face avant 3b du substrat 3, le fil 2 comportant une première portion dopée 10 en contact avec la couche de nucléation 5, une zone active 30 et une seconde portion dopée 20 ;  at least one three-dimensional semiconductor structure 2, here in the form of a wire, which extends from the nucleation layer 5 along a longitudinal axis Δ oriented substantially orthogonal to the plane (X, Y) of the front face 3b of the substrate 3, the wire 2 comprising a first doped portion 10 in contact with the nucleation layer 5, an active zone 30 and a second doped portion 20;
- une couche de seconde électrode de polarisation 6, en contact avec la seconde portion dopée 20.  a layer of second polarization electrode 6, in contact with the second doped portion 20.
Le fil 2 représenté ici présente une configuration radiale, ou configuration cœur/coquille, dans la mesure où la seconde portion dopée 20 entoure et recouvre au moins en partie la zone active 30, et notamment la bordure latérale de celle-ci. Il présente donc une configuration qui se distingue de la configuration axiale dans laquelle la portion dopée n, la zone active et la portion dopée p sont empilées les unes sur les autres suivant l'axe longitudinal du fil, sans que la bordure latérale de la zone active ne soit sensiblement recouverte par la portion dopée p.  The wire 2 represented here has a radial configuration, or core / shell configuration, insofar as the second doped portion 20 surrounds and covers at least part of the active zone 30, and in particular the lateral edge thereof. It therefore has a configuration that differs from the axial configuration in which the n-doped portion, the active zone and the p-doped portion are stacked one over the other along the longitudinal axis of the wire, without the lateral edge of the zone. active is substantially covered by the p-doped portion.
Par bordure latérale ou supérieure, on entend une surface d'une partie du fil qui s'étend respectivement de manière sensiblement parallèle ou orthogonale à l'axe longitudinal Δ. Une bordure latérale peut être également appelée bordure radiale, ou flanc latéral. Une bordure supérieure peut être également appelée bordure axiale. By lateral or upper edge is meant a surface of a portion of the wire which extends respectively substantially parallel or orthogonal to the longitudinal axis Δ. A lateral border may also be called a radial edge, or lateral flank. An upper border can also be called an axial border.
Comme l'illustre la figure 3, les bordures latérales peuvent être inclinées lorsqu'elles forment un angle d'inclinaison a non nul avec l'axe longitudinal Δ. A titre d'exemple, la bordure 33 de la zone active 30 est ici dite inclinée dans la mesure où elle forme un angle d'inclinaison a vis-à-vis de l'axe longitudinal Δ différent de 0°, et en particulier strictement supérieur à 0° et strictement inférieur à 900, ou strictement inférieur à 0° et strictement supérieur à -900. De manière similaire, une bordure supérieure, par exemple ici la bordure 34 de la zone active 30, est dite inclinée lorsqu'elle forme un angle d'inclinaison β vis-à-vis de l'axe longitudinal Δ différent de 900, et en particulier strictement supérieur à 900 et strictement inférieur à 1800, ou strictement inférieur à 900 et strictement supérieur à 0°.As illustrated in Figure 3, the lateral edges may be inclined when they form a non-zero inclination angle with the longitudinal axis Δ. By way of example, the edge 33 of the active zone 30 is here called inclined insofar as it forms an angle of inclination with respect to the longitudinal axis Δ other than 0 °, and in particular strictly greater than 0 ° and strictly less than 90 0 , or strictly less than 0 ° and strictly greater than -90 0 . Similarly, an upper edge, for example here the edge 34 of the active zone 30, is said to be inclined when it forms an angle of inclination β with respect to the longitudinal axis Δ other than 90 ° , and in particular strictly greater than 90 ° and strictly less than 180 ° , or strictly less than 90 ° and strictly greater than 0 °.
Le substrat 3 est ici une structure semiconductrice, par exemple en silicium. Il peut être monobloc ou formé d'un empilement de couches tel qu'un substrat du type SOI (acronyme de Silicon On Insulator, en anglais). Plus largement, le substrat peut être en un matériau semiconducteur, par exemple en silicium, en germanium, en carbure de silicium, ou en un composé III-V ou II- VI. Il peut également être en un matériau métallique ou en un matériau isolant. Il peut comporter une couche de graphène, de sulfure ou séléniure de molybdène (M0S2, MoSe2), ou de tout autre matériau équivalent. Dans cet exemple, le substrat est en silicium monocristallin de type n fortement dopé. The substrate 3 is here a semiconductor structure, for example silicon. It may be monoblock or formed of a stack of layers such as a substrate of the SOI type (acronym for Silicon On Insulator). More broadly, the substrate may be of a material semiconductor, for example silicon, germanium, silicon carbide, or a compound III-V or II-VI. It can also be made of a metallic material or an insulating material. It may comprise a layer of graphene, molybdenum sulphide or selenide (MoS2, MoSe2), or any other equivalent material. In this example, the substrate is made of highly doped n-type monocrystalline silicon.
La première électrode de polarisation 4 est en contact avec le substrat 3, ici électriquement conducteur, par exemple au niveau de sa face arrière 3a. Elle peut être réalisée en aluminium ou en tout autre matériau adapté.  The first polarization electrode 4 is in contact with the substrate 3, here electrically conductive, for example at its rear face 3a. It can be made of aluminum or any other suitable material.
La couche de nucléation 5 est réalisée en un matériau favorisant la nucléation et la croissance des fils, par exemple en nitrure d'aluminium (AIN) ou en oxyde d'aluminium (AI2O3), en nitrure de magnésium (MgxNy), en nitrure ou en carbure d'un métal de transition ou en tout autre matériau adapté. L'épaisseur de la couche de nucléation peut être de l'ordre de quelques nanomètres ou quelques dizaines de nanomètres. Dans cet exemple, la couche de nucléation est en AIN. The nucleation layer 5 is made of a material that promotes the nucleation and growth of the yarns, for example aluminum nitride (AlN) or aluminum oxide (Al 2 O 3 ), magnesium nitride (MgxN y ), nitride or carbide of a transition metal or any other suitable material. The thickness of the nucleation layer may be of the order of a few nanometers or a few tens of nanometers. In this example, the nucleation layer is AlN.
La première portion dopée 10 du fil repose sur le substrat 3 au niveau de la couche de nucléation 5. Elle présente une forme filaire qui s'étend suivant l'axe longitudinal Δ, et forme le cœur du fil en configuration cœur/coquille. Elle présente une extrémité 11, opposée au substrat, délimitée longitudinalement par une face dite supérieure 14. La face supérieure 14 s'étend ici de manière sensiblement orthogonale à l'axe longitudinal Δ mais peut être inclinée vis-à-vis de l'axe Δ, voire être formée d'une ou plusieurs faces dites alors élémentaires. The first doped portion 10 of the wire rests on the substrate 3 at the level of the nucleation layer 5. It has a wire shape which extends along the longitudinal axis Δ, and forms the heart of the wire heart / shell configuration. It has an end 11, opposite to the substrate, delimited longitudinally by a so-called upper face 14. The upper face 14 extends here substantially orthogonal to the longitudinal axis Δ but can be inclined with respect to the axis Δ, or even be formed of one or more so-called then elementary faces.
La première portion dopée 10 est réalisée en un premier composé semiconducteur, qui peut être choisi parmi les composés III-V comportant au moins un élément de la colonne III et au moins un élément de la colonne V du tableau périodique, parmi les composés II-VI comportant au moins un élément de la colonne II et au moins un élément de la colonne VI, ou parmi les éléments ou composés IV comportant au moins un élément de la colonne IV. A titre d'exemple, des composés III-V peuvent être des composés III-N, tels que GaN, InGaN, AlGaN, AIN, InN ou AlInGaN, voire des composés comportant un élément de la colonne V du type arsenic ou phosphore, par exemple l'AsGa ou l'InP. Par ailleurs, des composés II-VI peuvent être CdTe, HgTe, CdHgTe, ZnO, ZnMgO, CdZnO ou CdZnMgO. Enfin, des éléments ou composés IV peuvent être utilisés, tels que Si, C, Ge, SiC, SiGe, ou GeC. La première portion est dopée selon un premier type de conductivité.  The first doped portion 10 is made of a first semiconductor compound, which may be chosen from compounds III-V comprising at least one element of column III and at least one element of column V of the periodic table, among the compounds II- VI comprising at least one element of column II and at least one element of column VI, or of elements or compounds IV having at least one element of column IV. By way of example, III-V compounds may be III-N compounds, such as GaN, InGaN, AlGaN, AlN, InN or AlInGaN, or even compounds comprising an arsenic or phosphorus-type V column element, for example. example AsGa or InP. On the other hand, compounds II-VI can be CdTe, HgTe, CdHgTe, ZnO, ZnMgO, CdZnO or CdZnMgO. Finally, elements or compounds IV may be used, such as Si, C, Ge, SiC, SiGe, or GeC. The first portion is doped according to a first type of conductivity.
Dans cet exemple, la première portion dopée 10 est réalisée en GaN dopé de type n, notamment par du silicium. La première portion dopée 10 présente ici un diamètre moyen approximativement égal au diamètre local. Le diamètre moyen de la première portion dopée 10 peut être compris entre îonm et ιομηι, par exemple compris entre soonm et 5μηι, et est ici sensiblement égal à ΐμηι. La hauteur de la première portion dopée peut être comprise entre îoonm et ιομηι, par exemple comprise entre soonm et 5μηι, et est ici sensiblement égale à 5μηι. In this example, the first doped portion 10 is made of n-type doped GaN, in particular with silicon. The first doped portion 10 here has an average diameter approximately equal to the local diameter. The average diameter of the first doped portion 10 can be between 1 m and ιομηι, for example between soonm and 5μηι, and is here substantially equal to ΐμηι. The height of the first doped portion may be between 1oonm and ιομηι, for example between soonm and 5μηι, and here is substantially equal to 5μηι.
Dans cet exemple, une couche diélectrique 7 recouvre ici la couche de nucléation 5 et forme un masque de croissance autorisant l'épitaxie des fils à partir d'ouvertures débouchant localement sur la couche de nucléation, et une seconde couche diélectrique 8 recouvre la bordure latérale de la première portion dopée 10. In this example, a dielectric layer 7 here covers the nucleation layer 5 and forms a growth mask allowing the epitaxy of the son from openings opening locally on the nucleation layer, and a second dielectric layer 8 covers the lateral border of the first doped portion 10.
La zone active 30 est la portion du fil 2 au niveau de laquelle est émis l'essentiel du rayonnement lumineux du fil. Elle comprend au moins un puits quantique réalisé en un composé semiconducteur présentant une énergie de bande interdite inférieure à celles de la première portion dopée 10 et de la seconde portion dopée 20. Elle s'étend à partir de l'extrémité 11 de la première portion dopée 10 et plus précisément à partir de la face supérieure 14. Comme détaillé plus loin, la zone active 30 peut comporter un unique puits quantique ou des puits quantiques multiples sous forme de couches ou de boîtes intercalées entre des couches barrières.  The active zone 30 is the portion of the wire 2 at which most of the light radiation of the wire is emitted. It comprises at least one quantum well made of a semiconductor compound having a band gap energy lower than that of the first doped portion 10 and the second doped portion 20. It extends from the end 11 of the first portion doped 10 and more precisely from the upper face 14. As detailed below, the active zone 30 may comprise a single quantum well or multiple quantum wells in the form of layers or boxes interposed between barrier layers.
La zone active 30 comporte une portion monocristalline dite élargie 31 qui s'étend suivant l'axe longitudinal Δ à partir de la face supérieure 14 de l'extrémité 11 de la première portion dopée 10.  The active zone 30 comprises a so-called widened monocrystalline portion 31 which extends along the longitudinal axis Δ from the upper face 14 of the end 11 of the first doped portion 10.
La portion monocristalline élargie 31 est formée d'un monocristal d'un second composé semiconducteur, différent du premier composé semiconducteur dans le sens où il comprend au moins un élément supplémentaire non contenu dans le premier composé. Le second composé est ainsi formé d'un mélange du premier composé et d'au moins un élément supplémentaire. La proportion atomique de l'élément supplémentaire est choisie en fonction des propriétés optiques et/ou électroniques recherchées et notamment du spectre d'émission du fil. A titre d'exemple, dans le cas d'une première portion dopée 10 réalisée en GaN, le second composé est préférentiellement de l'InGaN, de formule générale InxGa(i-x)N, avec par exemple un pourcentage atomique d'indium de l'ordre de 18%. Le second composé semiconducteur de la portion monocristalline élargie 31 peut être non intentionnellement dopé, ou dopé selon le même type de conductivité et éventuellement au même niveau de dopage que la première portion dopée 10. The expanded monocrystalline portion 31 is formed of a single crystal of a second semiconductor compound, different from the first semiconductor compound in the sense that it comprises at least one additional element not contained in the first compound. The second compound is thus formed of a mixture of the first compound and at least one additional element. The atomic proportion of the additional element is chosen as a function of the optical and / or electronic properties sought, and in particular of the emission spectrum of the wire. By way of example, in the case of a first doped portion 10 made of GaN, the second compound is preferably InGaN, of general formula In x Ga (i- x ) N, with, for example, an atomic percentage of indium of the order of 18%. The second semiconductor compound of the expanded monocrystalline portion 31 may be unintentionally doped or doped according to the same type of conductivity and possibly at the same doping level as the first doped portion 10.
La portion monocristalline élargie 31 est formée d'un unique cristal du second composé semiconducteur, délimité par une base 32 en contact avec la face supérieure 14 de la première portion dopée 10, une bordure latérale 33 et une bordure supérieure 34. Comme détaillé plus loin, les bordures latérale 33 et supérieure 34 peuvent présenter des faces semi- polaires, c'est-à-dire des faces inclinées vis-à-vis de l'axe longitudinal Δ. The enlarged monocrystalline portion 31 is formed of a single crystal of the second semiconductor compound, delimited by a base 32 in contact with the upper face 14 of the first doped portion 10, a lateral edge 33 and an upper edge 34. detailed later, the lateral edges 33 and upper 34 may have semi-polar faces, that is to say faces inclined vis-à-vis the longitudinal axis Δ.
La portion monocristalline 31 est dite élargie dans la mesure où elle présente un diamètre moyen supérieur au diamètre moyen de la première portion dopée 10. Elle présente ainsi un diamètre moyen qui peut être compris entre 1,1 et 20 fois le diamètre moyen de la première portion dopée 10, par exemple compris entre 2 et 10 fois le diamètre moyen de la première portion dopée 10, et est ici sensiblement égal à 5μηι.  The monocrystalline portion 31 is said to be enlarged insofar as it has a mean diameter greater than the average diameter of the first doped portion 10. It thus has a mean diameter which may be between 1.1 and 20 times the average diameter of the first doped portion 10, for example between 2 and 10 times the average diameter of the first doped portion 10, and is here substantially equal to 5μηι.
De plus, la portion monocristalline élargie 31 peut présenter une épaisseur moyenne supérieure à îonm qui est l'ordre de grandeur de l'épaisseur critique du second composé semiconducteur, ici l'InGaN. L'épaisseur locale est l'épaisseur de la portion monocristalline élargie 31 suivant un axe donné parallèle à l'axe longitudinal Δ à partir de la surface supérieure de la première portion dopée. L'épaisseur moyenne est la moyenne, par exemple arithmétique, des épaisseurs locales. L'épaisseur moyenne peut être comprise entre îonm et 2θμηι, par exemple comprise entre soonm et ιομηι, et est ici sensiblement égale à 5μηι. La zone active 30 comporte au moins un puits quantique, qui recouvre ici au moins en partie la portion monocristalline élargie 31, et en particulier ses bordures latérale 33 et supérieure 34. Dans cet exemple, la zone active comporte des puits quantiques multiples 35 se présentant sous forme d'un empilement de couches, dont une ou plusieurs couches forment des puits quantiques intercalés entre deux couches barrières.  In addition, the enlarged monocrystalline portion 31 may have an average thickness greater than 1 μm which is the order of magnitude of the critical thickness of the second semiconductor compound, here InGaN. The local thickness is the thickness of the enlarged monocrystalline portion 31 along a given axis parallel to the longitudinal axis Δ from the upper surface of the first doped portion. The average thickness is the average, for example arithmetic, of the local thicknesses. The average thickness may be between 1 μm and 2θμηι, for example between soonm and ιομηι, and is here substantially equal to 5μηι. The active zone 30 comprises at least one quantum well, which here covers at least in part the enlarged monocrystalline portion 31, and in particular its lateral edges 33 and upper 34. In this example, the active zone comprises multiple quantum wells 35 presenting in the form of a stack of layers, one or more layers forming quantum wells interposed between two barrier layers.
Les couches formant les puits quantiques, et de préférence également les couches barrières, sont réalisées dans un matériau semiconducteur à base du second composé semiconducteur, c'est-à-dire comportant au moins les mêmes éléments que le second composé semiconducteur, ici en InGaN. Elles sont de préférence réalisées dans le même second composé semiconducteur, avec des fractions molaires différentes pour les couches barrières et pour les puits quantiques. The layers forming the quantum wells, and preferably also the barrier layers, are made of a semiconductor material based on the second semiconductor compound, that is to say having at least the same elements as the second semiconductor compound, here in InGaN . They are preferably made in the same second semiconductor compound, with different mole fractions for the barrier layers and for the quantum wells.
Les couches barrières peuvent ainsi être réalisées en InxiGai-xiN avec une proportion atomique d'indium xi comprise entre 15% et 23% environ, par exemple égale à 18% environ, et les couches formant les puits quantiques peuvent être réalisées en Inx2Gai-x2N avec une proportion atomique d'indium x2 comprise entre 22% et 30% environ, par exemple égale à 25% environ, permettant ici d'obtenir une longueur d'onde d'émission comprise entre 495nm et sôonm environ, par exemple égale à soonm environ. La proportion atomique x2 est supérieure à la proportion atomique xi. La diode électroluminescente est alors d'émettre un rayonnement lumineux dans le vert, avec un bon rendement lumineux dans la mesure où le rendement quantique interne est amélioré par le fait qu'on limite le désaccord de maille entre la portion monocristalline en InGaN et les puits quantiques multiples alors même que la première portion dopée est réalisée en GaN. De préférence, la portion monocristalline en InGaN présente une proportion atomique égale à celle de la couche barrière qui est en contact avec elle. The barrier layers can thus be made of In x iGai x iN with an atomic proportion of indium xi of between approximately 15% and 23%, for example equal to approximately 18%, and the layers forming the quantum wells can be produced by In x2 Gai-x 2 N with an atomic proportion of indium x2 of between approximately 22% and 30%, for example equal to approximately 25%, thereby making it possible to obtain an emission wavelength of between 495nm and sôonm about, for example equal to about min. The atomic proportion x2 is greater than the atomic proportion xi. The light-emitting diode is then to emit light radiation in the green, with a good light output insofar as the internal quantum efficiency is improved by the fact that the mesh mismatch between the monocrystalline portion in InGaN and the wells is limited. multiple quantum then same as the first doped portion is made of GaN. Preferably, the monocrystalline portion of InGaN has an atomic proportion equal to that of the barrier layer which is in contact with it.
La seconde portion dopée 20 forme une couche qui recouvre et entoure au moins en partie la zone active 30, c'est-à-dire ici la portion monocristalline élargie 31 et les puits quantiques multiples 35. Elle est réalisée en un composé semiconducteur dopé d'un second type de conductivité opposé au premier type. Le composé semiconducteur peut être le premier composé semiconducteur, à savoir ici le GaN, ou de préférence le second composé semiconducteur, à savoir ici l'InGaN. Il peut également comporter un ou plusieurs éléments supplémentaires. Dans cet exemple, la seconde portion dopée 20 est réalisée en InGaN, et est dopée de type p, notamment par du magnésium. L'épaisseur de la seconde portion dopée peut être comprise entre 20 nm et 500 nm, par exemple de l'ordre de 150 nm.  The second doped portion 20 forms a layer that covers and at least partially surrounds the active zone 30, that is to say here the expanded single crystal portion 31 and the multiple quantum wells. It is made of a d-doped semiconductor compound. a second type of conductivity opposite to the first type. The semiconductor compound may be the first semiconductor compound, namely here GaN, or preferably the second semiconductor compound, namely here InGaN. It may also include one or more additional elements. In this example, the second doped portion 20 is made of InGaN, and is p-type doped, in particular with magnesium. The thickness of the second doped portion may be between 20 nm and 500 nm, for example of the order of 150 nm.
La seconde portion dopée 20 peut comprendre une couche de blocage d'électrons (non représentée) située à l'interface avec la zone active 30. La couche de blocage d'électrons peut ici être formée d'un composé ternaire III-N, par exemple de l'AlGaN ou de ΓΑΐΙηΝ, avantageusement dopée p. Elle permet d'accroître le taux de recombinaisons radiatives au sein de la zone active.  The second doped portion 20 may comprise an electron-blocking layer (not shown) located at the interface with the active zone 30. The electron-blocking layer can here be formed of a ternary compound III-N, for example example of AlGaN or ΓΑΐΙηΝ, advantageously doped p. It makes it possible to increase the rate of radiative recombinations within the active zone.
La seconde électrode de polarisation 6 recouvre ici la seconde portion dopée 20 et est adaptée à appliquer une polarisation électrique au fil 2. Elle est réalisée en un matériau sensiblement transparent vis-à-vis du rayonnement lumineux émis par le fil, par exemple de l'oxyde d'indium étain (ITO, pour Indium Tin Oxide). Elle présente une épaisseur de quelques nanomètres à quelques dizaines ou centaines de nanomètres.  The second polarization electrode 6 here covers the second doped portion 20 and is adapted to apply an electrical polarization to the wire 2. It is made of a substantially transparent material vis-à-vis the light radiation emitted by the wire, for example the indium tin oxide (ITO, for Indium Tin Oxide). It has a thickness of a few nanometers to a few tens or hundreds of nanometers.
Ainsi, lorsqu'une différence de potentiel est appliquée au fil 2 dans un sens direct par l'intermédiaire des deux électrodes de polarisation, le fil 2 émet un rayonnement lumineux dont le spectre d'émission présente un pic d'intensité à une longueur d'onde dépendant principalement de la composition du ou des puits quantiques.  Thus, when a potential difference is applied to the wire 2 in a direct direction via the two polarization electrodes, the wire 2 emits light radiation whose emission spectrum has a peak intensity at a length of wave depending mainly on the composition of the quantum well.
Il ressort ainsi que le fil, en configuration radiale, comprend une zone active à puits quantique comportant une portion monocristalline élargie, celle-ci reposant sur une face supérieure de la première portion dopée, cette face supérieure formant ainsi un germe de nucléation pour la portion monocristalline élargie. It thus emerges that the wire, in radial configuration, comprises a quantum well active zone comprising an enlarged monocrystalline portion, the latter lying on an upper face of the first doped portion, this upper face thus forming a nucleation seed for the portion expanded monocrystalline.
Ainsi, malgré le désaccord de maille entre le premier composé semiconducteur de la première portion dopée et le second composé semiconducteur de la portion monocristalline élargie, cette dernière présente une structure cristallographique sensiblement relaxée, c'est- à-dire non contrainte, son paramètre de maille étant sensiblement identique au paramètre de maille naturel du composé. Cela s'explique par le fait qu'à la différence du fil décrit en référence à la figure 1, la surface permettant la nucléation de la portion monocristalline élargie est réduite et inférieure au diamètre moyen de la portion monocristalline. Thus, despite the mesh mismatch between the first semiconductor compound of the first doped portion and the second semiconductor compound of the enlarged monocrystalline portion, the latter has a substantially relaxed, i.e. unconstrained, crystallographic structure. mesh being substantially identical to the parameter natural mesh of the compound. This is explained by the fact that unlike the wire described with reference to Figure 1, the area for nucleation of the expanded monocrystalline portion is reduced and less than the average diameter of the monocrystalline portion.
La portion monocristalline élargie présente alors une bonne qualité cristalline, avec une densité limitée de défauts structuraux. La densité de défauts structuraux, c'est-à-dire le nombre de défauts par unité de volume, diminue en particulier avec l'augmentation du volume de la portion monocristalline élargie. En effet, les défauts structuraux, du type dislocation, sont essentiellement issus d'une relaxation plastique du second composé semiconducteur dans la zone de nucléation à partir de la face supérieure de la première portion dopée, et ne sont sensiblement pas engendrés par l'élargissement de la portion monocristalline élargie.  The expanded monocrystalline portion then has a good crystalline quality, with a limited density of structural defects. The density of structural defects, that is to say the number of defects per unit volume, decreases in particular with the increase in the volume of the expanded monocrystalline portion. Indeed, the structural defects, of the dislocation type, are essentially derived from a plastic relaxation of the second semiconductor compound in the nucleation zone from the upper face of the first doped portion, and are not substantially generated by the enlargement. of the enlarged monocrystalline portion.
Ainsi, la zone active peut comporter au moins un puits quantique, réalisé en un matériau à base du second composé semiconducteur, et qui repose sur la portion monocristalline élargie ou qui est formé par celle-ci. On limite ainsi dans la zone active, en particulier au niveau du ou des puits quantiques, les effets du désaccord de maille entre le premier composé semiconducteur de la première portion dopée et le matériau semiconducteur formant le ou les puits quantiques. Le ou les puits quantiques présentent alors une qualité cristalline améliorée et donc un rendement quantique interne augmenté.  Thus, the active zone may comprise at least one quantum well, made of a material based on the second semiconductor compound, and which rests on the enlarged monocrystalline portion or is formed by it. In the active zone, and particularly at the level of the quantum well (s), the effects of the mismatch between the first semiconductor compound of the first doped portion and the semiconductor material forming the quantum well (s) are thus limited. The quantum well (s) then have an improved crystalline quality and thus an increased internal quantum yield.
Il est alors possible de réduire voire de s'affranchir des limites, mentionnées en référence à la figure 1, relatives à l'épaisseur des puits quantiques et/ou à la proportion atomique de l'élément supplémentaire. Il est en effet possible de réaliser une zone active dont le ou les puits quantiques présentent une grande épaisseur, supérieure à l'épaisseur critique, et/ou présentent une proportion atomique importante de l'élément supplémentaire, ici d'indium. It is then possible to reduce or even overcome the limits mentioned with reference to FIG. 1 relating to the thickness of the quantum wells and / or to the atomic proportion of the additional element. It is indeed possible to produce an active zone whose quantum well or wells have a large thickness, greater than the critical thickness, and / or have a significant atomic proportion of the additional element, here of indium.
Enfin, dans l'exemple de la figure 2, les puits quantiques multiples recouvrent et entourent au moins en partie la portion monocristalline élargie, ce qui permet d'obtenir une plus grande surface d'émission. Cette surface d'émission augmentée, conjuguée au rendement quantique interne optimisé, permet d'augmenter également le rendement optique du fil, celui-ci étant défini comme le rapport du flux lumineux émis sur la puissance électrique absorbée. Finally, in the example of FIG. 2, the multiple quantum wells cover and surround at least in part the enlarged monocrystalline portion, which makes it possible to obtain a larger emission area. This increased emission surface, combined with optimized internal quantum efficiency, also increases the optical performance of the wire, the latter being defined as the ratio of the light flux emitted on the absorbed electrical power.
Lorsque la zone active est formée à base du deuxième composé semiconducteur, par exemple à base d'InGaN, on limite les contraintes mécaniques dans la zone active alors même que la première portion dopée est réalisée en le premier composé semiconducteur, par exemple en GaN. On améliore ainsi le meilleur rendement quantique. Il est possible de réaliser une zone active de plus grande épaisseur et/ou d'incorporer davantage d'élément supplémentaire du second composé semiconducteur, par exemple d'indium dans le cas de l'InGaN. Dans le cas où la zone active est formée des puits quantiques multiples 35 qui recouvrent au moins une partie de la portion monocristalline élargie 31, formés d'une alternance de couches barrières présentant une première valeur Inxi non nulle de proportion atomique en indium et de couches formant des puits quantiques présentant une deuxième valeur Inx2 de proportion atomique en indium supérieure à la première valeur Inxl, il est possible de réaliser une zone active dont la valeur xi est comprise entre 15% et 23% et dont la valeur x2 est comprise entre 22% et 30%, alors même que la première portion dopée est réalisée en GaN. La diode est en mesure d'émettre un rayonnement lumineux dans le vert, avec un bon rendement lumineux dans la mesure où le rendement quantique interne est amélioré. When the active area is formed based on the second semiconductor compound, for example based on InGaN, limiting the mechanical stresses in the active area while the first doped portion is made of the first semiconductor compound, for example GaN. This improves the best quantum efficiency. It is possible to make an active zone of greater thickness and / or to incorporate more additional element of the second semiconductor compound, for example indium in the case of InGaN. In the case where the active zone is formed of multiple quantum wells 35 which cover at least a portion of the enlarged monocrystalline portion 31, formed of an alternation of barrier layers having a first non-zero value In xi of indium atomic proportion and of quantum well forming layers having a second value In x2 of indium atomic proportion higher than the first value In xl , it is possible to make an active zone whose value xi is between 15% and 23% and whose value x2 is between 22% and 30%, even though the first doped portion is made of GaN. The diode is able to emit light radiation in the green, with a good light output as far as the internal quantum efficiency is improved.
Un exemple de procédé de réalisation du dispositif optoélectronique illustré sur la figure 2 est maintenant décrit. Dans cet exemple, le fil 2 est réalisé par croissance épitaxiale par dépôt chimique en phase vapeur organométallique (MOCVD, pour Metal-Organic Chem ical Vapor Déposition, en anglais) et sont ici réalisés à base de GaN. An exemplary method for producing the optoelectronic device illustrated in FIG. 2 is now described. In this example, the yarn 2 is made by epitaxial growth by chemical vapor deposition organometallic (MOCVD, for Metal-Organic Chemical Vapor Deposition, in English) and here are made based on GaN.
Dans le cadre d'une croissance épitaxiale de type MOCVD, les paramètres influençant la croissance épitaxiale sont notamment : In the context of an epitaxial growth of MOCVD type, the parameters influencing the epitaxial growth are in particular:
le rapport V/III nominal, défini comme le rapport entre le flux molaire d'éléments de la colonne V sur le flux molaire d'éléments de la colonne III, c'est-à-dire ici le rapport N/Ga lors de la croissance de la première portion dopée réalisée en GaN, et le rapport N/(Ga+In), lors de la croissance de la portion monocristalline élargie et les puits quantiques multiples, réalisés en InGaN ;  the nominal V / III ratio, defined as the ratio between the molar flow of elements of column V on the molar flow of elements of column III, that is to say here the N / Ga ratio during the growth of the first doped portion made of GaN, and the ratio N / (Ga + In), during the growth of the expanded monocrystalline portion and the multiple quantum wells, made in InGaN;
le rapport H2/N2), défini comme le rapport entre la proportion de flux molaire de H2 dans le gaz porteur de H2 et de N2, à savoir φΗ2/ (φΗ2+φ 2), sur la proportion de flux molaire de N2, à savoir φ 2/(φΗ2+φ 2), ψΗ2 et φΝ2 étant respectivement les flux molaires d'hydrogène et d'azote ; the ratio H 2 / N 2 ), defined as the ratio between the proportion of molar flux of H 2 in the carrier gas of H 2 and N 2 , namely φ Η 2 / (φ 2 + φ 2 ), on the proportion molar flow of N 2, namely φ 2 / (φΗ 2 + φ 2) and φ Ν2 ψΗ 2 being respectively the mole ratios of hydrogen and nitrogen stream;
la température de croissance T, mesurée ici au niveau du substrat.  the growth temperature T, measured here at the substrate.
Lors d'une première étape, on forme la première portion dopée 10 par croissance épitaxiale à partir de la couche de nucléation 5. L'épitaxie peut être effectuée à partir d'ouvertures formées dans un masque de croissance 7 en un matériau diélectrique, par exemple du Si3N4, préalablement déposé sur la couche de nucléation 5. In a first step, the first doped portion 10 is formed by epitaxial growth from the nucleation layer 5. The epitaxy can be performed from openings formed in a growth mask 7 of a dielectric material, by example of Si 3 N 4 , previously deposited on the nucleation layer 5.
La température de croissance est portée à une première valeur ΊΊ, par exemple comprise entre 950°C et noo°C, et notamment comprise entre 990°C et io6o°C. Le rapport V/III nominal, ici le rapport N/Ga, présente une première valeur (V/III)i comprise entre 10 et 100 environ, par exemple sensiblement égale à 30. Les éléments du groupe III et du groupe V sont issus de précurseurs injectés dans le réacteur d'épitaxie, par exemple le triméthylgallium (TMGa) ou le triéthylgallium (TEGa) pour le gallium, et l'ammoniac (NH3) pour l'azote. Le rapport H2/N2 présente une première valeur (H2/N2)i supérieure ou égale à 60/40, de préférence supérieure ou égale à 70/30, voire davantage, par exemple sensiblement égale à 90/10. La pression peut être fixée à 8oombar environ. The growth temperature is brought to a first value ΊΊ, for example between 950 ° C and noo ° C, and especially between 990 ° C and io6o ° C. The nominal V / III ratio, here the N / Ga ratio, has a first value (V / III) i of between 10 and approximately 100, for example substantially equal to 30. The elements of group III and of group V come from precursors injected into the epitaxial reactor, for example the trimethylgallium (TMGa) or triethylgallium (TEGa) for gallium, and ammonia (NH 3 ) for nitrogen. The ratio H 2 / N 2 has a first value (H 2 / N 2 ) i greater than or equal to 60/40, preferably greater than or equal to 70/30, or even more, for example substantially equal to 90/10. The pressure can be set at about 8mbar.
On obtient ainsi une première portion dopée 10 qui présente une forme d'un fil qui s'étend suivant l'axe longitudinal Δ. Le premier composé semiconducteur de la première portion dopée 10, à savoir ici le GaN, est dopé de type n par du silicium. La première portion dopée 10 présente ici une hauteur de 5μηι environ et un diamètre moyen de ΐμηι environ. Elle présente une face supérieure 14, opposée au substrat 3 et orientée suivant l'axe cristallographique c, sensiblement plane. Cette face supérieure 14 forme la face axiale 14 de l'extrémité de la première portion dopée, et assure la fonction de surface de nucléation pour la formation de la portion monocristalline élargie. This gives a first doped portion 10 which has the shape of a wire which extends along the longitudinal axis Δ. The first semiconductor compound of the first doped portion 10, namely here GaN, is n-doped with silicon. The first doped portion 10 here has a height of approximately 5μηι and an average diameter of ΐμηι approximately. It has an upper face 14, opposite the substrate 3 and oriented along the crystallographic axis c, substantially flat. This upper face 14 forms the axial face 14 of the end of the first doped portion, and provides the nucleation surface function for the formation of the enlarged monocrystalline portion.
La formation d'une couche diélectrique 8 recouvrant la bordure latérale 13 de la première portion dopée 10 peut être effectuée simultanément à la formation de la première portion dopée. Pour cela, un précurseur d'un élément supplémentaire, par exemple du silane (SiH4) dans le cas du silicium, est injecté avec les précurseurs mentionnés précédemment, avec un rapport des flux molaires du précurseur du gallium sur le précurseur du silicium de préférence compris entre 500 et 5000 environ. On obtient ainsi une couche 8 de nitrure de silicium, par exemple du Si3N4 d'une épaisseur de l'ordre de îonm, qui revêt la bordure latérale 13 de la première portion dopée, ici sur toute sa hauteur. The formation of a dielectric layer 8 covering the lateral edge 13 of the first doped portion 10 can be performed simultaneously with the formation of the first doped portion. For this, a precursor of an additional element, for example silane (SiH 4 ) in the case of silicon, is injected with the precursors mentioned above, with a ratio of the molar flows of the gallium precursor on the silicon precursor preferably. between about 500 and 5000. Thus, a layer 8 of silicon nitride, for example Si 3 N 4 of a thickness of the order of 1 μm, which covers the lateral edge 13 of the first doped portion, here over its entire height.
Lors d'une seconde étape, on forme la portion monocristalline élargie 31 par croissance épitaxiale à partir de la face supérieure 14 de la première portion dopée 10.  In a second step, the enlarged monocrystalline portion 31 is formed by epitaxial growth from the upper face 14 of the first doped portion 10.
La température de croissance est portée à une seconde valeur T2 inférieure à la valeur ΊΊ, par exemple comprise entre 700°C et 8oo°C, ici égale à 750°C environ. De manière à former un second composé semiconducteur comportant les éléments du premier composé ainsi qu'au moins un élément supplémentaire, on maintient l'injection des précurseurs des éléments III et V et on ajoute un précurseur de l'élément supplémentaire, par exemple du triméthylindium (TMIn) dans le cas de l'indium. Le rapport V/III nominal présente une seconde valeur (V/III)2 supérieure à la valeur (V/III)!, par exemple comprise entre 500 et 5000 environ, ici sensiblement égale à 1500. De plus, le rapport H2/N2 présente une seconde valeur (H2/N2)2 inférieure à la valeur (H2/N2)i et inférieure ou égale à 40/60, de préférence inférieure ou égale à 30/70, voire davantage, par exemple sensiblement égale à 3/97. Par ailleurs, la pression peut rester inchangée, et l'injection du précurseur de silicium est préalablement stoppée. The growth temperature is brought to a second value T 2 lower than the value ΊΊ, for example between 700 ° C. and 8oo ° C., here equal to about 750 ° C. In order to form a second semiconductor compound comprising the elements of the first compound and at least one additional element, the injection of the precursors of the elements III and V is maintained and a precursor of the additional element, for example trimethylindium, is added. (TMIn) in the case of indium. The nominal V / III ratio has a second value (V / III) 2 greater than the value (V / III), for example between about 500 and 5000, here substantially equal to 1500. Moreover, the ratio H 2 / N 2 has a second value (H 2 / N 2 ) 2 less than the value (H 2 / N 2 ) i and less than or equal to 40/60, preferably less than or equal to 30/70, or even more, for example substantially equal to 3/97. Furthermore, the pressure can remain unchanged, and the injection of the silicon precursor is previously stopped.
On obtient ainsi une portion monocristalline 31 du second composé semiconducteur, ici de l'InGaN avec une proportion atomique d'indium de l'ordre de 18%, par croissance épitaxiale à partir de la face supérieure 14 de la première portion dopée 10. De plus, l'augmentation de la valeur du rapport V/III, associée à la diminution du rapport H2/N2, conduit à l'élargissement de la portion monocristalline d'InGaN. La portion monocristalline élargie peut être non intentionnellement dopée, mais est avantageusement dopée selon le même type de conductivité et de préférence au même niveau de dopage que la première portion dopée 10, limitant ainsi la résistance série associée aux portions 10, 31. Thus, a monocrystalline portion 31 of the second semiconductor compound, here of InGaN with an atomic proportion of indium of the order of 18%, is obtained by epitaxial growth. from the upper face 14 of the first doped portion 10. In addition, the increase in the value of the V / III ratio, associated with the reduction of the H 2 / N 2 ratio, leads to the enlargement of the monocrystalline portion. InGaN. The expanded monocrystalline portion may be unintentionally doped, but is advantageously doped according to the same type of conductivity and preferably at the same doping level as the first doped portion 10, thus limiting the series resistance associated with the portions 10, 31.
Lors d'une troisième étape, on forme des puits quantiques multiples 35 par croissance épitaxiale à partir de la portion monocristalline élargie 31, ici au niveau de la bordure latérale 33 et de la bordure supérieure 34.  In a third step, multiple quantum wells are formed by epitaxial growth from the expanded monocrystalline portion 31, here at the lateral border 33 and the upper border 34.
Plus précisément, on forme un empilement de couches barrières et d'au moins une couche formant un puits quantique, lesdites couches étant alternées dans le sens de la croissance épitaxiale. Les couches formant les puits quantiques et les couches barrières sont avantageusement réalisées dans un composé semiconducteur qui comprend les mêmes éléments que le second composé semiconducteur, à savoir ici l'InGaN, avec des proportions atomiques différentes pour les couches de puits quantiques et les couches barrières. A titre d'exemple, les couches barrières sont réalisées dans le second composé semiconducteur, ici de l'InxGa(i-x)N avec x égal à 18% atomique environ, et les couches de puits quantiques sont également réalisées en InyGa(i-y)N, avec y supérieur à x, par exemple de l'ordre de 25% atomique, de manière à améliorer le confinement quantique des porteurs de charge dans les puits quantiques. More specifically, a stack of barrier layers and at least one layer forming a quantum well is formed, said layers being alternated in the direction of epitaxial growth. The layers forming the quantum wells and the barrier layers are advantageously made in a semiconductor compound which comprises the same elements as the second semiconductor compound, namely here InGaN, with different atomic proportions for the quantum well layers and the barrier layers. . For example, the barrier layers are made in the second semiconductor compound, here In x Ga (i- x ) N with x equal to about 18 atomic%, and the quantum well layers are also made in y Ga (i- y ) N, with y greater than x, for example of the order of 25 atomic%, so as to improve the quantum confinement of the charge carriers in the quantum wells.
La formation des couches barrières et des couches de puits quantiques peut être réalisée à une valeur T3 de température de croissance sensiblement égale à la valeur T2, à savoir ici 750°C. Le rapport V/III présente une valeur (V /III)3 sensiblement égale à la valeur (V /III)2. Le rapport H2/N2 présente une valeur sensiblement égale à la valeur (H2/N2)2 lors de la formation des couches barrières et présente une valeur sensiblement inférieure à la valeur (H2/N2)2 lors de la formation des couches de puits quantiques, par exemple 1/99. La pression peut rester inchangée. On obtient ainsi des couches barrières en InGaN avec 18% atomique environ d'indium et des couches de puits quantiques en InGaN avec 25% atomique environ d'indium. The formation of the barrier layers and quantum well layers can be carried out at a growth temperature value T 3 substantially equal to the value T 2 , namely here 750 ° C. The ratio V / III has a value (V / III) 3 substantially equal to the value (V / III) 2 . The ratio H 2 / N 2 has a value substantially equal to the value (H 2 / N 2 ) 2 during the formation of the barrier layers and has a value substantially lower than the value (H 2 / N 2 ) 2 during the formation of quantum well layers, for example 1/99. The pressure can remain unchanged. Thus, InGaN barrier layers with about 18 atomic% indium and InGaN quantum well layers are obtained with about 25 atomic% of indium.
Lors d'une quatrième étape, on forme la seconde portion dopée 20 par croissance épitaxiale de manière à recouvrir et entourer au moins en partie la zone active 30. In a fourth step, the second doped portion 20 is formed by epitaxial growth so as to cover and surround at least part of the active zone 30.
Pour cela, la température de croissance peut être portée à une quatrième valeur T4 supérieure à la valeur T3, par exemple de l'ordre de 885°C. Le rapport V/III peut être porté à une quatrième valeur (V/III)4 supérieure à la valeur (V/III)3, par exemple de l'ordre de 4000. Le rapport H2/N2 est porté à une quatrième valeur (H2/N2)4 supérieure à la valeur (H2/N2)2, par exemple de l'ordre de 15/85. Enfin, la pression peut être diminuée à une valeur de l'ordre de 300mbar. For this, the growth temperature can be increased to a fourth value T 4 greater than the value T 3 , for example of the order of 885 ° C. The ratio V / III may be increased to a fourth value (V / III) 4 greater than the value (V / III) 3 , for example of the order of 4000. The ratio H 2 / N 2 is increased to a fourth value (H 2 / N 2 ) 4 greater than the value (H 2 / N 2 ) 2 , for example of the order of 15/85. Finally, the pressure can be decreased to a value of the order of 300mbar.
On obtient ainsi une seconde portion dopée 20, par exemple en GaN ou InGaN dopé de type p, qui recouvre et entoure ici continûment la zone active 30, c'est-à-dire les puits quantiques multiples ainsi que la portion monocristalline élargie. La seconde portion dopée 20 forme ainsi la coquille du fil de configuration cœur/coquille.  A second doped portion 20 is thus obtained, for example p-type doped GaN or InGaN, which continuously covers and surrounds here the active zone 30, that is to say the multiple quantum wells as well as the enlarged monocrystalline portion. The second doped portion 20 thus forms the shell of the core / shell configuration wire.
Enfin, la seconde électrode de polarisation 6 peut être déposée de manière à être en contact avec au moins une partie de la seconde portion dopée 20. La seconde électrode 6 est réalisée en un matériau électriquement conducteur et transparent au rayonnement lumineux émis par les fils. Ainsi, l'application d'une différence de potentiel en direct aux fils par les deux électrodes de polarisation conduit à l'émission d'un rayonnement lumineux dont les propriétés du spectre d'émission dépend de la composition du ou des puits quantiques dans la zone active.  Finally, the second polarization electrode 6 may be deposited so as to be in contact with at least a portion of the second doped portion 20. The second electrode 6 is made of an electrically conductive material and transparent to the light radiation emitted by the son. Thus, the application of a direct potential difference to the wires by the two polarization electrodes leads to the emission of light radiation whose properties of the emission spectrum depends on the composition of the quantum well or quantum wells. active area.
Selon un mode de réalisation, comme le représente les figures 2 et 3, la portion monocristalline élargie 31 présente des faces semi-polaires, formées par les bordures latérale 33 et supérieure 34. Les bordures latérale et supérieure forment des faces inclinées vis-à-vis de l'axe longitudinal Δ et correspondent à des plans cristallins semi-polaires. Ainsi, la bordure latérale inclinée correspond à des plans cristallins voisins du type (3 o -3 -2) incliné d'un angle a d'environ 200 par rapport à l'axe longitudinal Δ, et la bordure supérieure inclinée correspond des plans cristallins voisins du type (1 o -1 3) incliné d'un angle β d'environ 1200 par rapport à l'axe longitudinal Δ. According to one embodiment, as shown in FIGS. 2 and 3, the enlarged monocrystalline portion 31 has semi-polar faces, formed by the lateral 33 and upper 34 edges. The lateral and upper edges form faces inclined vis-à- screws of the longitudinal axis Δ and correspond to semi-polar crystalline planes. Thus, the inclined lateral edge corresponds to adjacent crystalline planes of the type (3 o -3 -2) inclined at an angle α of about 20 ° relative to the longitudinal axis Δ, and the inclined upper edge corresponds to planes neighboring crystalline type (1 o -1 3) inclined at an angle β of about 120 0 relative to the longitudinal axis Δ.
La différence d'inclinaison entre les différentes faces semi-polaires 33, 34 conduit à la formation de couches de puits quantiques qui diffèrent mutuellement par l'épaisseur et/ou la proportion atomique des éléments. En effet, dans le cas d'une couche formant un puits quantique réalisé en InGaN, le taux d'incorporation d'indium et/ou l'épaisseur de la couche formée est différent selon que le dépôt est effectué sur une face plus ou moins inclinée vis- à-vis de l'axe longitudinal Δ. Cela se traduit alors par des différences de propriétés optiques, notamment une différence de longueur d'onde d'émission, entre les puits quantiques reposant sur les faces semi-polaires. Le rayonnement lumineux émis par un tel fil peut alors présenter un spectre d'émission élargi lorsqu'il provient des puits quantiques situés sur les différentes faces semi-polaires.  The difference in inclination between the different semi-polar faces 33, 34 leads to the formation of quantum well layers which differ mutually by the thickness and / or the atomic proportion of the elements. Indeed, in the case of a quantum well forming layer made of InGaN, the incorporation rate of indium and / or the thickness of the layer formed is different depending on whether the deposition is carried out on one side more or less inclined vis-à-vis the longitudinal axis Δ. This then results in differences in optical properties, including a difference in emission wavelength, between the quantum wells resting on the semi-polar faces. The light radiation emitted by such a wire can then have an expanded emission spectrum when it comes from the quantum wells located on the different semi-polar faces.
La figure 4 illustre schématiquement une vue partielle en coupe d'une variante du premier mode de réalisation d'un dispositif optoélectronique 1 comportant des structures semiconductrices tridimensionnelles 2 formant des diodes électroluminescentes filaires en configuration radiale et à puits quantiques multiples. FIG. 4 schematically illustrates a partial sectional view of a variant of the first embodiment of an optoelectronic device 1 comprising structures 3-dimensional semiconductors 2 forming wired light emitting diodes in radial configuration and with multiple quantum wells.
Le dispositif optoélectronique 1 se distingue de celui représenté sur la figure 2 essentiellement en ce que la couche diélectrique 8 recouvrant la bordure latérale 13 de la première portion dopée 10 ne s'étend pas sur toute la hauteur de cette dernière. Dans cet exemple, la couche diélectrique 8 s'étend à partir de la couche de nucléation 5 sur une hauteur Hx inférieure à la hauteur H2 de la première portion dopée 10. Par hauteur, on entend l'étendue longitudinale, suivant l'axe longitudinal Δ, d'une couche ou portion. Ainsi, une zone dite supérieure 13I1 de la bordure latérale 13 de la première portion dopée 10, qui s'étend à partir de la hauteur Hx jusqu'à la hauteur H2, n'est pas recouverte par la couche diélectrique 8, et est appelée zone libre. The optoelectronic device 1 differs from that shown in Figure 2 essentially in that the dielectric layer 8 covering the lateral edge 13 of the first doped portion 10 does not extend over the entire height of the latter. In this example, the dielectric layer 8 extends from the nucleation layer 5 over a height H x less than the height H 2 of the first doped portion 10. By height, we mean the longitudinal extent, according to the longitudinal axis Δ, of a layer or portion. Thus, a so-called upper zone 13I1 of the lateral edge 13 of the first doped portion 10, which extends from the height H x to the height H 2 , is not covered by the dielectric layer 8, and is called free zone.
Lors de la formation épitaxiale de la portion monocristalline élargie 31, une seconde portion élargie 36, peut être formée à partir de la bordure latérale 13 de la première portion dopée 10, au niveau de la zone libre 13I1. Cette seconde portion élargie 36 est réalisée également en le second composé semiconducteur et présente un diamètre moyen supérieur au diamètre moyen de la première portion dopée. Elle est ici recouverte par les puits quantiques multiples 35, par la seconde portion dopée 20 et par la seconde électrode de polarisation 6.  During the epitaxial formation of the enlarged monocrystalline portion 31, a second enlarged portion 36 may be formed from the lateral edge 13 of the first doped portion 10 at the free zone 13I1. This second enlarged portion 36 is also made of the second semiconductor compound and has a mean diameter greater than the average diameter of the first doped portion. Here it is covered by the multiple quantum wells 35, the second doped portion 20 and the second polarization electrode 6.
Cette seconde portion élargie 36 est formée par croissance épitaxiale à partir de la zone libre 13I1 de la bordure latérale 13 de la première portion dopée 10, et à ce titre, subie des contraintes mécaniques liées au désaccord de maille avec le premier composé semiconducteur, dans la mesure où elle présente une surface de nucléation importante avec la première portion dopée 10. Aussi, la qualité cristalline de la seconde portion élargie 36 est moindre que celle de la portion monocristalline élargie 31.  This second enlarged portion 36 is formed by epitaxial growth from the free zone 13I1 of the lateral edge 13 of the first doped portion 10, and as such, undergone mechanical stresses related to the mismatch with the first semiconductor compound, in the extent that it has a large nucleation surface with the first doped portion 10. Also, the crystalline quality of the second enlarged portion 36 is less than that of the enlarged monocrystalline portion 31.
En variante (non représentée), le fil 2 peut ne pas comporter de couche diélectrique 8 recouvrant au moins en partie la bordure latérale 13 de la première portion dopée 10. La seconde portion élargie 36 peut alors recouvrir la bordure latérale 13 de la première portion dopée, sur sensiblement toute la hauteur H2. Le masque de croissance 7, avantageusement diélectrique, assure alors l'isolation électrique entre la seconde électrode de polarisation et le substrat conducteur. Alternatively (not shown), the wire 2 may not have a dielectric layer 8 covering at least part of the lateral edge 13 of the first doped portion 10. The second enlarged portion 36 can then cover the lateral edge 13 of the first portion doped over substantially the entire height H 2 . The growth mask 7, advantageously dielectric, then provides electrical isolation between the second bias electrode and the conductive substrate.
La figure 5 illustre schématiquement une vue partielle en coupe d'un second mode de réalisation d'un dispositif optoélectronique 1 comportant des structures semiconductrices tridimensionnelles 2 formant des diodes électroluminescentes filaires en configuration radiale et à puits quantique unique. Le dispositif optoélectronique 1 se distingue de celui représenté sur la figure 2 essentiellement en ce que la zone active 30 comporte un puits quantique unique formé par la portion monocristalline élargie 31. FIG. 5 schematically illustrates a partial cross-sectional view of a second embodiment of an optoelectronic device 1 comprising three-dimensional semiconductor structures 2 forming wire electroluminescent diodes in radial configuration and with a single quantum well. The optoelectronic device 1 differs from that shown in FIG. 2 essentially in that the active zone 30 comprises a single quantum well formed by the enlarged monocrystalline portion 31.
La zone active 30 comporte ainsi un puits quantique unique réalisé dans le second composé semiconducteur, ici de l'InGaN, formé du premier composé semiconducteur, ici du GaN, dans lequel est incorporé au moins un élément supplémentaire, ici de l'indium. La proportion atomique des éléments du second composé semiconducteur InxGa(i-x)N est de préférence sensiblement homogène au sein du puits quantique, et le second composé semiconducteur est de préférence non intentionnellement dopé. The active zone 30 thus comprises a single quantum well made in the second semiconductor compound, here InGaN, formed of the first semiconductor compound, here GaN, in which is incorporated at least one additional element, here indium. The atomic proportion of the elements of the second In x Ga (i- x ) N semiconductor compound is preferably substantially homogeneous within the quantum well, and the second semiconductor compound is preferably unintentionally doped.
Le puits quantique unique d'InGaN forme un monocristal 31 qui s'étend à partir de la face supérieure 14 de la première portion dopée 10 et présente un diamètre moyen supérieur au diamètre moyen de la première portion dopée 10. Il comporte une base 32 en contact avec la face supérieure 14 de la première portion dopée 10, une bordure latérale 33 et une bordure supérieure 34. Les bordures latérale 33 et supérieure 34 présentent dans cet exemple des faces semi-polaires, c'est-à-dire des faces inclinées vis-à-vis de l'axe longitudinal Δ. The single quantum well of InGaN forms a monocrystal 31 which extends from the upper face 14 of the first doped portion 10 and has a mean diameter greater than the average diameter of the first doped portion 10. It comprises a base 32 in contact with the upper face 14 of the first doped portion 10, a lateral edge 33 and an upper edge 34. The lateral edges 33 and upper 34 have in this example semi-polar faces, that is to say, inclined faces vis-à-vis the longitudinal axis Δ.
La portion monocristalline élargie 31 est recouverte au moins en partie par la seconde portion dopée 20, qui revêt ici la bordure latérale 33 et la bordure supérieure 34. La seconde portion dopée 20 est en contact avec la seconde électrode 6 de polarisation.  The enlarged monocrystalline portion 31 is covered at least in part by the second doped portion 20, which here covers the lateral edge 33 and the upper edge 34. The second doped portion 20 is in contact with the second polarization electrode 6.
Dans cet exemple, la portion monocristalline élargie 31 est réalisée en InGaN avec une proportion atomique d'indium de l'ordre de 18% permettant d'obtenir une longueur d'onde d'émission centrée sur 420nm à 440nm, voire de 25% pour obtenir une longueur d'onde d'émission de l'ordre de soonm. Le diamètre moyen de la portion monocristalline élargie 31 est de l'ordre de 5μηι et son épaisseur moyenne est de l'ordre de 5μηι. La portion monocristalline élargie 31 présente ainsi, par son épitaxie à partir d'une surface réduite de nucléation, à savoir la face supérieure 14 de la première portion dopée 10, une bonne qualité cristalline dont la densité de défauts structuraux diminue avec son volume.  In this example, the expanded monocrystalline portion 31 is made of InGaN with an atomic proportion of indium of the order of 18% making it possible to obtain an emission wavelength centered on 420 nm at 440 nm or even 25% for obtain a transmission wavelength of the order of soonm. The mean diameter of the enlarged monocrystalline portion 31 is of the order of 5μηι and its average thickness is of the order of 5μηι. The expanded monocrystalline portion 31 thus has, by its epitaxy from a reduced nucleation surface, namely the upper face 14 of the first doped portion 10, a good crystalline quality whose density of structural defects decreases with its volume.
Les figures 6 et 7 illustrent schématiquement des vues partielles en coupe de deux variantes de la polarisation d'un dispositif optoélectronique 1 comportant des structures semiconductrices tridimensionnelles 2 similaires à celle représentée sur la figure 4. FIGS. 6 and 7 schematically illustrate partial sectional views of two variants of the polarization of an optoelectronic device 1 comprising three-dimensional semiconductor structures 2 similar to that shown in FIG. 4.
Dans cet exemple, les fils 2 comportent une zone active 30 à portion monocristalline élargie 31 revêtue au moins en partie par des puits quantiques multiples 35, eux-mêmes étant revêtus par la seconde portion dopée 20.  In this example, the yarns 2 comprise an active zone 30 with an enlarged monocrystalline portion 31 coated at least in part by multiple quantum wells 35, themselves being coated by the second doped portion 20.
La portion monocristalline élargie 31 est formée d'un monocristal du second composé semiconducteur, ici de l'InGaN, présentant des faces semi-polaires formées par les bordures latérale 33 et supérieure 34. Comme mentionné précédemment, les puits quantiques ne présentent pas les mêmes propriétés optiques du fait de différences d'épaisseur et/ou de proportion atomique d'indium, selon qu'ils sont disposés sur la face semi-polaire de la bordure supérieure 34 ou sur la face semi-polaire de la bordure latérale 33. The expanded monocrystalline portion 31 is formed of a single crystal of the second semiconductor compound, here of InGaN, having semi-polar faces formed by the borders Lateral 33 and higher 34. As mentioned above, quantum wells do not have the same optical properties due to differences in thickness and / or atomic proportion of indium, depending on whether they are arranged on the semi-polar face of the upper edge 34 or on the semi-polar face of the lateral edge 33.
Dans la variante illustrée sur la figure 6, les fils 2 se distinguent de celui représenté sur la figure 4 essentiellement en ce que la seconde électrode de polarisation 6 se présente, non plus sous la forme d'une couche recouvrant continûment la seconde portion dopée 20, mais sous forme d'une couche agencée de manière à polariser essentiellement les puits quantiques situés au niveau de la bordure supérieure inclinée 34. In the variant illustrated in FIG. 6, the wires 2 differ from that shown in FIG. 4 essentially in that the second polarization electrode 6 is no longer in the form of a layer continuously covering the second doped portion 20 , but in the form of a layer arranged to substantially polarize the quantum wells located at the inclined upper edge 34.
Plus précisément, le dispositif optoélectronique comporte une couche épaisse 9 en un matériau diélectrique, disposée entre les fils 2 sur une hauteur telle qu'elle recouvre la première portion dopée 10 ainsi que la partie de la seconde portion dopée 20 située au niveau de la bordure latérale inclinée 33. Le matériau diélectrique est au moins en partie transparent vis-à-vis du spectre d'émission des fils et présente un indice de réfraction choisi de manière à permettre l'extraction du rayonnement lumineux hors des fils. Le matériau diélectrique peut être, entre autres, un oxyde de silicium ou un nitrure d'aluminium ou de silicium. Sur la couche épaisse diélectrique 9 est déposée la seconde électrode de polarisation 6, sous forme d'une couche en un matériau conducteur et transparent vis-à-vis du spectre d'émission des fils, cette couche conductrice recouvrant la partie de la seconde portion dopée 20 située au niveau de la bordure supérieure inclinée 34. More specifically, the optoelectronic device comprises a thick layer 9 of a dielectric material, disposed between the wires 2 to a height such that it covers the first doped portion 10 and the portion of the second doped portion 20 located at the edge The dielectric material is at least partly transparent with respect to the emission spectrum of the wires and has a refractive index chosen so as to allow the light radiation to be extracted from the wires. The dielectric material may be, inter alia, a silicon oxide or an aluminum or silicon nitride. On the thick dielectric layer 9 is deposited the second polarization electrode 6, in the form of a layer of a conductive material and transparent vis-à-vis the emission spectrum of the son, this conductive layer covering the portion of the second portion doped 20 located at the inclined upper edge 34.
Ainsi, la seconde portion dopée 20 comporte une partie située au niveau de la bordure supérieure inclinée 34 qui est en contact avec la seconde électrode de polarisation 6, ainsi qu'une partie située au niveau de la bordure latérale inclinée 33 qui est en contact avec la couche épaisse diélectrique 9.  Thus, the second doped portion 20 has a portion located at the inclined upper edge 34 which is in contact with the second bias electrode 6, and a portion at the inclined lateral edge 33 which is in contact with the the dielectric thick layer 9.
Dans le cas d'une seconde portion dopée 20 réalisée en GaN dopé de type p ou en InGaN dopée de type p, la résistance électrique de cette portion 20 est telle que les lignes de champ électrique sont orientées de manière sensiblement rectiligne dans l'épaisseur de la seconde portion dopée 20 à partir de l'électrode 6, et ne s'étendent sensiblement pas suivant les directions transversales, dans l'épaisseur de la portion 20. Aussi, seule la partie de la seconde portion dopée 20 en contact avec l'électrode 6 est apte à être polarisée, la partie de la seconde portion dopée située au niveau de la bordure latérale inclinée 33 et qui n'est pas en contact avec l'électrode 6 n'étant sensiblement pas polarisée par l'électrode 6. In the case of a second doped portion 20 made of p-type doped GaN or p-type doped InGaN, the electrical resistance of this portion 20 is such that the electric field lines are oriented substantially rectilinearly in the thickness. of the second doped portion 20 from the electrode 6, and do not extend substantially in the transverse directions, in the thickness of the portion 20. Also, only the portion of the second doped portion 20 in contact with the 6 is able to be polarized, the portion of the second doped portion located at the inclined lateral edge 33 and which is not in contact with the electrode 6 being substantially not polarized by the electrode 6.
Dans la variante illustrée sur la figure 7, le dispositif optoélectronique 1 comporte deux secondes électrodes de polarisation, dites supérieure 6h et inférieure 6b, agencées de manière à polariser, pour l'électrode supérieure 6h, essentiellement la partie de la seconde portion dopée 20 située au niveau de la bordure supérieure inclinée 34, et pour l'électrode inférieure 6b, essentiellement la partie de la seconde portion dopée 20 située au niveau de la bordure latérale inclinée 33. L'électrode 6b repose sur une couche diélectrique 9b et l'électrode 6h repose sur une couche diélectrique 9I1. In the variant illustrated in FIG. 7, the optoelectronic device 1 comprises two second polarization electrodes, called the upper 6h and the lower 6b electrodes, arranged in such a way as to polarize, for the upper electrode 6h, essentially the portion of the second doped portion 20 located at the inclined upper edge 34, and for the electrode lower 6b, essentially the portion of the second doped portion 20 located at the inclined lateral edge 33. The electrode 6b rests on a dielectric layer 9b and the electrode 6h rests on a dielectric layer 9I1.
Les secondes électrodes supérieure 6h et inférieure 6b sont adaptées à appliquer un potentiel électrique distinct ou identique aux deux parties de la seconde portion dopée 20, selon les propriétés recherchées du spectre d'émission.  The second upper 6h and lower 6b electrodes are adapted to apply a distinct or identical electrical potential to the two parts of the second doped portion 20, according to the desired properties of the emission spectrum.
Ici également, dans le cas d'une seconde portion dopée 20 réalisée en GaN dopé de type p ou en InGaN dopé de type p, les deux parties de la seconde portion dopée 20 sont polarisées par l'une et/ou l'autre des électrodes supérieure 6h et inférieure 6b, sensiblement sans interférences ou diaphotie (crosstalk, en anglais), du fait de la résistance électrique de la portion 20.  Here also, in the case of a second doped portion 20 made of p-type doped GaN or p-type doped InGaN, the two parts of the second doped portion 20 are polarized by one and / or the other upper 6h and lower 6b electrodes, substantially without interference or crosstalk (in English), because of the electrical resistance of the portion 20.
Bien entendu, ces exemples sont donnés à titre purement illustratif. D'autres agencements de la seconde électrode de polarisation sont possibles, par exemple pour ne polariser que la zone de la seconde portion dopée située au niveau de la bordure latérale inclinée. Par ailleurs, la ou les secondes électrodes de polarisation peuvent être agencées sous forme, non pas de couche sensiblement plane, mais de couches structurées comme l'illustre le document US8937297.  Of course, these examples are given for purely illustrative purposes. Other arrangements of the second biasing electrode are possible, for example to polarize only the area of the second doped portion located at the inclined lateral edge. Furthermore, the second or second polarization electrodes can be arranged in the form of not a substantially flat layer, but structured layers as illustrated in US8937297.
Des modes de réalisation particuliers viennent d'être décrits. Différentes variantes et modifications apparaîtront à l'homme du métier. On a décrit des structures semiconductrices tridimensionnelles adaptées à émettre un rayonnement lumineux à partir d'un signal électrique, formant ainsi des diodes électroluminescentes. Alternativement, les structures peuvent être adaptées à détecter un rayonnement lumineux incident et à produire en réponse un signal électrique, formant ainsi une photodiode. Les applications peuvent concerner le domaine de l'optoélectronique ou du photovoltaïque. Specific embodiments have just been described. Various variations and modifications will occur to those skilled in the art. Three-dimensional semiconductor structures adapted to emit light radiation from an electrical signal have been described, thereby forming light-emitting diodes. Alternatively, the structures may be adapted to detect incident light radiation and to respond to an electrical signal thereby forming a photodiode. Applications may be in the field of optoelectronics or photovoltaics.

Claims

REVENDICATIONS
1. Dispositif optoélectronique (ι), comportant au moins une structure semiconductrice tridimensionnelle (2) s'étendant suivant un axe longitudinal (Δ) sensiblement orthogonal à un plan d'un substrat (3) sur lequel elle repose, et comportant : An optoelectronic device (ι), comprising at least one three-dimensional semiconductor structure (2) extending along a longitudinal axis (Δ) substantially orthogonal to a plane of a substrate (3) on which it rests, and comprising:
- une première portion dopée (10), s'étendant à partir du substrat (3) suivant l'axe longitudinal (Δ), et réalisée en un premier composé semiconducteur ;  a first doped portion (10), extending from the substrate (3) along the longitudinal axis (Δ), and made of a first semiconductor compound;
- une zone active (30) comportant au moins un puits quantique, et s'étendant à partir de la première portion dopée (10), la zone active comportant une portion élargie, s'étendant à partir d'une face supérieure (14) d'une extrémité (11) de la première portion dopée (10) opposée au substrat (3), et présentant un diamètre moyen supérieur à celui de la première portion dopée (10),  an active zone (30) comprising at least one quantum well and extending from the first doped portion (10), the active zone comprising an enlarged portion extending from an upper face (14); one end (11) of the first doped portion (10) opposite the substrate (3), and having a mean diameter greater than that of the first doped portion (10),
- une seconde portion dopée (20), recouvrant au moins en partie la zone active (30) ; caractérisé en ce que :  a second doped portion (20) covering at least part of the active zone (30); characterized in that
- la portion élargie (31) est monocristalline, et est formée d'un monocristal d'un second composé semiconducteur formé d'un mélange du premier composé semiconducteur et d'au moins un élément supplémentaire ; et  - The enlarged portion (31) is monocrystalline, and is formed of a single crystal of a second semiconductor compound formed of a mixture of the first semiconductor compound and at least one additional element; and
la zone active est réalisée à base dudit second composé semiconducteur.  the active zone is made based on said second semiconductor compound.
2. Dispositif optoélectronique selon la revendication 1, dans lequel la zone active (30) comporte des puits quantiques multiples (35) qui recouvrent au moins une partie de la portion monocristalline élargie (31), formés d'une alternance de couches barrières présentant une première valeur (lnx non nulle de proportion atomique en ledit élément supplémentaire et de couches formant des puits quantiques présentant une deuxième valeur (Inx2) de proportion atomique en ledit élément supplémentaire supérieure à la première valeur (Inxi). An optoelectronic device according to claim 1, wherein the active area (30) comprises multiple quantum wells (35) which cover at least a portion of the enlarged single crystal portion (31) formed of alternating barrier layers having a plurality of first value (ln x nonzero atomic proportion to said additional element and quantum well forming layers having a second value (In x2 ) of atomic proportion to said additional element greater than the first value (In x i).
3. Dispositif optoélectronique selon la revendication 2, dans lequel la première valeur de proportion atomique en ledit élément supplémentaire des couches barrières est comprise entre 15% et 23% et la deuxième valeur de proportion atomique en ledit élément supplémentaire des puits quantiques est comprise entre 22% et 30%.  Optoelectronic device according to claim 2, wherein the first atomic proportion value in said additional element of the barrier layers is between 15% and 23% and the second atomic proportion value in said additional element of the quantum wells is between 22% and 23%. % and 30%.
4. Dispositif optoélectronique selon la revendication 2 ou 3, dans lequel le monocristal présente une proportion atomique en ledit élément supplémentaire égale à celle de la couche barrière en contact avec celui-ci. Optoelectronic device according to claim 2 or 3, wherein the single crystal has an atomic proportion to said additional element equal to that of the barrier layer in contact therewith.
5. Dispositif optoélectronique selon la revendication 1, dans lequel la portion monocristalline élargie (31) forme un unique puits quantique, le second composé semiconducteur étant de préférence non intentionnellement dopé. An optoelectronic device according to claim 1, wherein the expanded monocrystalline portion (31) forms a single quantum well, the second semiconductor compound preferably being unintentionally doped.
6. Dispositif optoélectronique selon l'une quelconque des revendications 1 à 5, dans lequel la portion monocristalline élargie (31) présente une épaisseur moyenne suivant l'axe longitudinal (Δ) supérieure à 10 nm. Optoelectronic device according to any one of claims 1 to 5, wherein the enlarged single crystal portion (31) has a mean thickness along the longitudinal axis (Δ) greater than 10 nm.
7. Dispositif optoélectronique selon l'une quelconque des revendications 1 à 6, dans lequel la portion monocristalline élargie (31) présente un diamètre moyen supérieur à 110% du diamètre moyen de la première portion dopée (10). Optoelectronic device according to any one of claims 1 to 6, wherein the enlarged monocrystalline portion (31) has an average diameter greater than 110% of the average diameter of the first doped portion (10).
8. Dispositif optoélectronique selon l'une quelconque des revendications 1 à 7, le premier composé semiconducteur est choisi parmi les composés III-V, les composés II-VI et les éléments ou composés IV, et de préférence est un composé III-N. Optoelectronic device according to any one of claims 1 to 7, the first semiconductor compound is selected from compounds III-V compounds II-VI and elements or compounds IV, and preferably is a compound III-N.
9. Dispositif optoélectronique selon l'une quelconque des revendications 1 à 8, le premier composé semiconducteur étant du GaN et le second composé semiconducteur étant de l'InGaN. Optoelectronic device according to any one of claims 1 to 8, the first semiconductor compound being GaN and the second semiconductor compound being InGaN.
10. Dispositif optoélectronique selon l'une quelconque des revendications 1 à 9, dans lequel la seconde portion dopée (20) est au moins en partie entourée par une électrode de polarisation (6). Optoelectronic device according to any one of claims 1 to 9, wherein the second doped portion (20) is at least partly surrounded by a bias electrode (6).
11. Dispositif optoélectronique selon l'une quelconque des revendications 2 à 10 dépendantes de la revendication 2, dans lequel la portion monocristalline élargie (31) présente au moins deux faces semi-polaires (33, 34) d'inclinaisons différentes par rapport à l'axe longitudinal (Δ), lesdites faces semi-polaires étant recouvertes par au moins un puits quantique (35) revêtu par la seconde portion dopée (20). An optoelectronic device according to any one of claims 2 to 10 dependent on claim 2, wherein the enlarged monocrystalline portion (31) has at least two semi-polar faces (33, 34) of different inclinations with respect to longitudinal axis (Δ), said semi-polar faces being covered by at least one quantum well (35) coated with the second doped portion (20).
12. Dispositif optoélectronique selon la revendication 11, comportant au moins deux électrodes de polarisation (6h, 6b) adaptées à polariser chacune une partie de la seconde portion dopée (20) située au niveau de l'une ou l'autre desdites faces semi-polaires (33, 34). Optoelectronic device according to claim 11, comprising at least two polarization electrodes (6h, 6b) each adapted to polarize a portion of the second doped portion (20) located at one or other of said semi-faces. polar (33, 34).
13. Procédé de réalisation d'un dispositif optoélectronique (1) selon l'une quelconque des revendications précédentes, dans lequel la structure semiconductrice tridimensionnelle (2) est formée par dépôt chimique en phase vapeur, le premier composé semiconducteur étant un composé III-V. A method of producing an optoelectronic device (1) according to any one of the preceding claims, wherein the three-dimensional semiconductor structure (2) is formed by chemical vapor deposition, the first semiconductor compound being a III-V compound. .
14. Procédé de réalisation d'un dispositif optoélectronique (1) selon la revendication 13, dans lequel, lors de la formation de la première portion dopée (10), un rapport V/III entre un flux du gaz précurseur de l'élément V sur un flux du gaz précurseur de l'élément III présente une valeur inférieure ou égale à 100, et dans lequel lors de la formation de la portion monocristalline élargie (31), ledit rapport V/III présente une valeur supérieure ou égale à 500. 14. A method of producing an optoelectronic device (1) according to claim 13, wherein, during the formation of the first doped portion (10), a V / III ratio between a flow of the precursor gas of the element V a flow of the precursor gas of the element III has a value less than or equal to 100, and wherein during the formation of the enlarged monocrystalline portion (31), said V / III ratio has a value greater than or equal to 500.
15. Procédé de réalisation d'un dispositif optoélectronique (1) selon la revendication 13 ou 14, dans lequel, lors de la formation de la première portion dopée (10), un rapport H2/N2 entre une proportion de flux molaire d'hydrogène sur une proportion de flux molaire d'azote présente une valeur supérieure ou égale à 60/40, de préférence supérieure ou égale à 70/30, et dans lequel lors de la formation de la portion monocristalline élargie (31), ledit rapport H2/N2 présente une valeur inférieure ou égale à 40/60, de préférence inférieure ou égale à 30/70. 15. A method of producing an optoelectronic device (1) according to claim 13 or 14, wherein, during the formation of the first doped portion (10), a ratio H 2 / N 2 between a proportion of molar flux d hydrogen on a proportion of molar flow of nitrogen has a value greater than or equal to 60/40, preferably greater than or equal to 70/30, and wherein during the formation of the enlarged monocrystalline portion (31), said ratio H 2 / N 2 has a value less than or equal to 40/60, preferably less than or equal to 30/70.
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