CN212659825U - Quaternary system tensile strain semiconductor laser epitaxial wafer - Google Patents

Abstract

The invention relates to the technical field of semiconductors, in particular to a quaternary system tensile strain semiconductor laser epitaxial wafer, which is characterized in that: the grating structure sequentially comprises a substrate, a buffer layer, a grating layer, an InP cover layer, a covering layer, an isolating layer, a lower limiting layer, a lower gradient waveguide layer, a multi-quantum well layer, an upper gradient waveguide layer, an upper limiting layer, an upper cladding layer, an upper gradient layer and a contact layer from bottom to top, wherein N-face grating patterns are prepared on the grating layer and the InP cover layer. The laser epitaxial wafer prepared by the invention improves the transport speed of current carriers and the optical gain and reliability of the semiconductor laser.

Description

Quaternary system tensile strain semiconductor laser epitaxial wafer

Technical Field

The utility model relates to the field of semiconductor technology, especially, relate to a quaternary system tensile strain semiconductor laser epitaxial wafer.

Background

Since the semiconductor laser appeared in the early sixties of the last century, the semiconductor laser has been widely applied to the fields of daily life, industrial and agricultural production, national defense and military and the like of people due to the performance advantages of wide wavelength coverage range, compact structure, high reliability, easy integration and the like. The performance of semiconductor lasers depends to a large extent on the quality of semiconductor epitaxial wafers, and therefore the preparation of high-quality epitaxial wafers is critical for the preparation of high-performance semiconductor lasers. In particular, in the 80 s of the 20 th century, the quantum well structure has made the semiconductor laser a great leap. In the quantum well structure, when the thickness of the ultrathin active layer material is less than the de Broglie wavelength of electrons, the active region becomes a potential well region, the broadband system materials at two sides become barrier regions, and the motion of the electrons and the holes along the direction vertical to the well wall has the characteristic of quantization. The presence of strained quantum wells fundamentally changes the band structure of the semiconductor material. It is possible to obtain the band structure we need by adjusting the type of strain and the magnitude of the amount of strain. Up to now, a great leap has appeared in the performance of semiconductor devices, and the application of semiconductor lasers in many fields has been realized. At present, as a light source, a quantum well semiconductor laser has the advantages of small volume, low threshold current density, good temperature characteristic, large output power, good dynamic characteristic, direct modulation and the like, and then a grating is introduced for Distributed Feedback (DFB), so that the quantum well DFB laser becomes the most ideal light source in high-speed communication. The tensile stress quantum well brings new opportunities for high-speed laser application due to different energy band structures and carrier transport characteristics of the quantum well. However, in current communication applications, the most commonly used light source is based on a compressive strain quantum well, and in order to meet the requirement of high-speed applications of over 25G, the differential gain of the active region of the laser is generally improved by increasing the stress of the quantum well and the number of the quantum wells, but the excessive stress and the number of the quantum wells bring great challenges to the reliability of the device.

In view of the above, it is an urgent need in the art to provide a quaternary system tensile strained semiconductor laser epitaxial wafer to overcome the above technical defects.

Disclosure of Invention

An object of the utility model is to overcome prior art's shortcoming, provide a quaternary system tensile strain semiconductor laser epitaxial wafer, improved the speed of transport of current carrier and semiconductor laser's optical gain and reliability.

For solving the above technical problem, the technical scheme of the utility model is that: a quaternary system tensile strain semiconductor laser epitaxial wafer is characterized in that: the grating structure sequentially comprises a substrate, a buffer layer, a grating layer, an InP cover layer, a covering layer, an isolating layer, a lower limiting layer, a lower gradient waveguide layer, a multi-quantum well layer, an upper gradient waveguide layer, an upper limiting layer, an upper cladding layer, an upper gradient layer and a contact layer from bottom to top, wherein N-face grating patterns are prepared on the grating layer and the InP cover layer.

According to the technical scheme, the buffer layer is made of InP, the thickness of the InP is 500-1000nm, and the doping concentration is 1 multiplied by 10¹⁸~3×10¹⁸cm^-3The growth rate is between 0.4 and 0.6 nm/s.

According to the technical scheme, the grating layer is made of InGaAsP, the thickness of the grating layer is 10-50 nm, and the band gap wavelength is 1000-1300 nm.

According to the technical scheme, the grating duty cycle range of the grating layer is 20% -80%.

According to the technical scheme, the covering layer is made of InP and has the thickness of 30-150 nm.

According to the technical scheme, the multiple quantum well layer is formed by a plurality of In_x(Al_yGa_1-y)_1-xThe As quantum well material has tensile strain relative to the substrate, and the strain capacity is between-0.5% and-2.0%.

According to the technical scheme, a plurality ofBarrier layers between the quantum wells are stressed by compressive stress In_x(Al_yGa_1-y)_1-xAs is, the strain capacity is between +0.3% and + 1.5%.

According to the technical scheme, the logarithm of the quantum well is between 1 and 20, the thickness of the quantum well is between 5 and 15nm, and the thickness of the potential barrier is between 5 and 20 nm.

According to the technical scheme, the lower gradient waveguide layer and the upper gradient waveguide layer are In with gradually changed components_x(Al_yGa_1-y)_{1- x}As and Al components gradually change from 0.8-0.5, and x ranges from 0.4-0.6.

According to the technical scheme, the material of the lower limiting layer and the upper limiting layer is In_x(Al_yGa_1-y)_1-xAs, Al component content y is between 0.6 and 1, x ranges between 0.4 and 0.7.

By the above scheme, the utility model discloses a quaternary system tensile strain semiconductor laser epitaxial wafer, it cuts out the active region of design many pairs of quaternary system tensile strain InAlGaAs quantum wells through the energy band structure, improves semiconductor laser optical gain and reliability; the impedance of a carrier passing through the Bragg reflector is reduced through the design of the N-plane grating, and the carrier transport speed is improved; and designing the epitaxial wafer structure with high coupling efficiency by matching the structure parameters of the isolation layer with the theoretical model of the optical field distribution of the quantum well layer. The high-speed laser prepared by the epitaxial wafer is very suitable for the application requirements of high-speed optical transmission such as 5G communication.

Drawings

Fig. 1 is a schematic view of an overall structure of a laser epitaxial wafer according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a laser epitaxial wafer before a grating is prepared;

fig. 3 is a schematic structural diagram of a laser epitaxial wafer after a grating is prepared;

wherein: 1-a substrate; 2-a buffer layer; 3-a grating layer; 4-InP cover layer, 5-covering layer and 6-isolating layer; 7-a lower limiting layer; 8-a lower graded waveguide layer; 9-a multi-quantum well layer; 10-an upper graded waveguide layer; 11-an upper confinement layer; 12-upper cladding; 13-upper graded layer; 14-contact layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the following, many aspects of the present invention will be better understood with reference to the drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, in the several views of the drawings, like reference numerals designate corresponding parts.

The word "exemplary" or "illustrative" as used herein means serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" or "illustrative" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described below are exemplary embodiments provided to enable persons skilled in the art to make and use the examples of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. In other instances, well-known features and methods have been described in detail so as not to obscure the invention. For purposes of the description herein, the terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," and derivatives thereof shall relate to the invention as oriented in fig. 1. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

Referring to fig. 1, the present invention provides a quaternary system tensile strained semiconductor laser epitaxial wafer, which is different in that: the InP substrate comprises an InP substrate 1, a buffer layer 2, a grating layer 3, an InP cover layer 4, a covering layer 5, an isolation layer 6, a lower limiting layer 7, a lower gradient waveguide layer 8, a multi-quantum well layer 9, an upper gradient waveguide layer 10, an upper limiting layer 11, an upper cladding layer 12, an upper gradient layer 13 and a contact layer 14 from bottom to top in sequence, wherein N-face grating patterns are prepared on the grating layer 3 and the InP cover layer 4.

Preferably, the buffer layer 2 is made of InP, the thickness is 500-1000nm, and the doping concentration is 1 × 10¹⁸~3×10¹⁸cm^-3The growth rate is between 0.4 and 0.6 nm/s.

Preferably, the material of the grating layer 3 is InGaAsP, the thickness is 10 to 50nm, and the band gap wavelength is between 1000 to 1300 nm.

Preferably, the grating duty cycle of the grating layer 3 ranges from 20% to 80%.

Preferably, the material of the covering layer 5 is InP, and the thickness is 30-150 nm.

Preferably, the multiple quantum well layer 9 is composed of a plurality of In_x(Al_yGa_1-y)_1-xThe As quantum well material has tensile strain relative to the substrate, and the strain capacity is between-0.5% and-2.0%.

Preferably, the barrier layers between a plurality of said quantum wells are stressed by compressive stress In_x(Al_yGa_1-y)_1-xAs is, the strain capacity is between +0.3% and + 1.5%.

Preferably, the logarithm of the quantum well is between 1 and 20, the thickness of the quantum well is between 5 and 15nm, and the thickness of the potential barrier is between 5 and 20 nm.

Preferably, the lower graded waveguide layer 8 and the upper graded waveguide layer 10 are In graded composition_x(Al_yGa_1-y)_1-xAs and Al components gradually change from 0.8-0.5, and x ranges from 0.4-0.6.

Preferably, the material of the lower limiting layer 7 and the upper limiting layer 11 is In_x(Al_yGa_1-y)_1-xThe content y of As and Al components is between 0.6 and 1And x ranges from 0.4 to 0.7.

The embodiment of the utility model provides an in, the concrete step of preparation this quaternary system tensile strain semiconductor laser epitaxial wafer is as follows:

step 1: selecting an InP substrate 1, wherein the InP substrate 1 is an InP single crystal wafer with crystal orientation (001) and deflection angle of + -0.5^oWithin the range of 325-375 μm in thickness and with a doping concentration of (2-8). times.10¹⁸ cm^-3。

Step 2: depositing an InP buffer layer 2, a grating layer 3 and an InP cover layer 4 on the substrate 1 in sequence; the thickness of the InP buffer layer 2 is 500-1000nm, and the growth temperature is between 630 and 680^oBetween C, SiH is adopted₄As dopant, the doping concentration is 1 × 10¹⁸To 3X 10¹⁸cm^-3Meanwhile, the growth speed is about 0.4-0.6 nm/s, and the excessively fast growth speed is not beneficial to the formation of a high-quality buffer layer; the grating layer 3 is InGaAsP material, the band gap wavelength is between 1100-1200nm, the lattice mismatch degree is less than +/-500 ppm, and the total thickness is 20-40 nm. The InP cap layer 4 has a thickness of 5-20 nm.

And step 3: and manufacturing a grating pattern on the epitaxial substrate. Specifically, the substrate is cleaned by using an organic solvent, washed by using a large amount of deionized water and dried by spin-drying. The first-order Bragg grating required by manufacturing the DFB semiconductor laser epitaxial wafer is obtained after the processes of pre-baking, glue homogenizing, post-baking, electron beam exposure, developing, film hardening, etching, glue removing and the like. The duty ratio of 0.5 is obtained by the combination of the exposure time and the development time. The grating period is between 195 and 210nm, and the depth is set to 60 nm. After the manufacturing is finished, the surface appearance, the period and the depth of the grating are tested through an Atomic Force Microscope (AFM) and a Scanning Electron Microscope (SEM), and the manufactured graph is ensured to meet the design requirement. In this step, a pattern is etched on the grating layer 3 and the InP capping layer 4, and then the capping layer 5 and the subsequent layers continue to be epitaxially grown twice in the etched trench.

And 4, step 4: continuously growing a covering layer 5, an isolating layer 6, a lower limiting layer 7, a lower gradient waveguide layer 8, a multi-quantum well layer 9, an upper gradient waveguide layer 10, an upper limiting layer 11, an upper cladding layer 12, an upper gradient layer 13 and a contact layer 14 on a substrate with a grating pattern; in particular toAnd (3) cleaning the residual photoresist on the substrate manufactured in the step (3) by using a solvent, washing the substrate by using a large amount of deionized water, and drying the substrate by spin-drying. Then placing the substrate into an MOCVD growth reaction chamber, and fully desorbing the surface oxide layer of the substrate by heating. Wherein, the covering layer 5 is made of InP material and has a growth thickness of 50-100nm, so as to ensure that the grating layer is fully covered. The isolation layer 6 is made of InP material and has a thickness of 50-150 nm. The lower limiting layer 7 is matched In_x(Al_yGa_1-y)_1-xAs and Al component y is 0.9, the thickness is 10-30nm, the lower gradient waveguide layer 8 and the upper gradient waveguide layer 10 are In with gradually-changed components_x(Al_yGa_1-y)_1-xAs and Al components gradually change from 0.8 to 0.5, and x ranges from 0.4 to 0.6. Multiple quantum well layer 9 consisting of multiple In_x(Al_yGa_1-y)_1-xThe As quantum well consists of y in the range of 0-0.6, x in the range of 0-0.6, and quantum well material with tensile strain in the range of-0.5% to-2.0% relative to the substrate. Barrier layer formed by compressive stress In_x(Al_yGa_1-y)_1-xAs composition, the strain amount is between +0.3% and +1.5%, and the logarithm of quantum wells is between 4 and 10. The thickness of the quantum well is between 5 and 15 nm; the barrier thickness is between 5-15 nm. The upper limiting layer 11 is made of InAlAs material and has a thickness of 10-30 nm. The upper cladding layer 12 is InP material with P doping concentration of 8 × 10¹⁷To 2.5X 10¹⁸cm^-3And (6) gradually changing. The upper graded layer 13 is InGaAsP material, the forbidden band wavelength is 1100-1500nm, and the doping concentration is 3 × 10¹⁸cm^-3The contact layer 14 is InGaAs material with doping concentration greater than 5E18 cm^-3The growth temperature is lower than 650 ℃. In this example, the doping concentration of 2.5E19 cm is used^-3The growth temperature is 600 ℃, and the excessive growth temperature can cause the outward diffusion escape of Zn, thereby reducing the doping concentration of the contact layer and increasing the contact resistance.

The epitaxial material growth equipment is MOCVD, and the sources used in the epitaxial growth process are trimethyl indium (TMIn), trimethyl gallium (TMGa), triethyl gallium (TEGa), arsine (AsH 3), phosphine (PH 3), silane (SiH 4) and diethyl zinc (DEZn).

The embodiment of the utility model provides a based on energy band structural design, grow InP base semiconductor laser epitaxial substrate and secondary epitaxial material through MOCVD. The quaternary system tensile strain semiconductor laser epitaxial material is grown through Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD), and a grating microstructure is manufactured by combining holographic and electron beam exposure technologies, so that the high-speed low-power-consumption semiconductor laser epitaxial wafer is realized.

The foregoing is a more detailed description of the present invention that is presented in conjunction with specific embodiments, and it is not to be understood that the specific embodiments of the present invention are limited to these descriptions. To the utility model belongs to the technical field of ordinary technical personnel, do not deviate from the utility model discloses under the prerequisite of design, can also make a plurality of simple deductions or replacement, all should regard as belonging to the utility model discloses a protection scope.

Claims (8)

1. A quaternary system tensile strain semiconductor laser epitaxial wafer is characterized in that: the grating structure sequentially comprises a substrate, a buffer layer, a grating layer, an InP cover layer, a covering layer, an isolating layer, a lower limiting layer, a lower gradient waveguide layer, a multi-quantum well layer, an upper gradient waveguide layer, an upper limiting layer, an upper cladding layer, an upper gradient layer and a contact layer from bottom to top, wherein N-face grating patterns are prepared on the grating layer and the InP cover layer.

2. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 1, wherein: the buffer layer is made of InP, the thickness of the buffer layer is 500-1000nm, and the doping concentration is 1 multiplied by 10¹⁸~3×10¹⁸cm^-3The growth rate is between 0.4 and 0.6 nm/s.

3. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 1, wherein: the grating layer is made of InGaAsP, the thickness of the grating layer is 10-50 nm, and the band gap wavelength is 1000-1300 nm.

4. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 3, wherein: the grating duty cycle range of the grating layer is 20% -80%.

5. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 1, wherein: the covering layer is made of InP and has a thickness of 30-150 nm.

6. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 1, wherein: the multiple quantum well layer is composed of multiple In_x(Al_yGa_1-y)_1-xThe As quantum well material has tensile strain relative to the substrate, and the strain capacity is between-0.5% and-2.0%.

7. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 6, wherein: barrier layers between multiple quantum wells are stressed by compressive stress In_x(Al_yGa_1-y)_1-xAs is, the strain capacity is between +0.3% and + 1.5%.

8. The quaternary tensilely strained semiconductor laser epitaxial wafer of claim 7, wherein: the logarithm of the quantum well is between 1 and 20, the thickness of the quantum well is between 5 and 15nm, and the thickness of the potential barrier is between 5 and 20 nm.

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