A kind of epitaxial structure and its manufacturing method
Technical field
The present invention relates to semiconductor laser technique field, particularly a kind of epitaxial structure that can adjust internal optical field distribution
And its manufacturing method.
Background technology
At present, semiconductor laser is widely used for the various aspects of national economy, adds including daily electronic product, industry
Work, optical-fibre communications, medical treatment, scientific research and national defense applications etc..Semiconductor laser material generally use molecular beam epitaxy (MBE) or
The methods of metal organic chemical vapor deposition (MOCVD) grown on corresponding substrate material according to the structure being pre-designed and
Into.Typical semiconductor extension structure includes N-shaped covering, undoped active area and p-type covering, and wherein active area includes hair
The Quantum Well and ducting layer of light.
Reliability is a most important technical indicator of semiconductor laser.The reliability of laser and the power of device
Density is closely related, and density is bigger, and the possibility of component failure is bigger, and the service life is shorter.Reliability is by certain test-strips
Under part, the possibility of component failure characterizes.There are two kinds of failure modes for semiconductor laser at present:1) intracavitary light injury calamity
Become (COD), 2) Cavity surface light injury catastrophe (COMD).The failure of major part device is all by 2) Cavity surface light injury catastrophe at present
(COMD) caused by, the reason is that:1) destruction of laser lattice causes surface a large amount of non-radiative recombination center occur, compound
Center occurs non-radiative recombination in laser operational process and generates a large amount of heat, and the aggregation of big calorimetric leads to component failure;
2) for the semiconductor laser device containing aluminium element in material, after Cavity surface in an atmosphere cleavage, it is exposed to air
Aluminium in environment is easily aoxidized, so as to introduce more Cavity surface defects;3) Cavity surface of laser needs to plate other materials
Change emissivity of the light in Cavity surface, since the material characters such as the coefficient of thermal expansion of plated material and semi-conducting material exist very very much not
Together, it is possible to cause to fail in laser operational process.
The problem of above-mentioned device reliability, can be solved by reducing optical power density.For high power laser light, use
The epitaxial structure for reducing power density designs to realize;However, now, the greatest problem faced is:It is exported in face of higher power
Market demands, further by design reduce the optical power density in device and at Cavity surface it is more and more difficult in addition be difficult
It realizes.This is because the reduction of optical power density can influence the whole electro-optic conversion of threshold current, external quantum efficiency and device
The important parameters such as efficiency.
Invention content
The purpose of the present invention is to provide a kind of epitaxial structure and its manufacturing method, the raising of device reliability and right is realized
Spot size it is controllable.
The present invention provides a kind of epitaxial structure, the epitaxial structure includes substrate and lamination is set to along the first direction
First wave conducting shell, quantum well layer and second waveguide layer on the substrate, wherein in the second party perpendicular to the first direction
Upwards, the first wave conducting shell and second waveguide layer are divided into quantum well mixing enhancement region and quantum well mixing inhibition zone,
Described in quantum well mixing enhancement region be used to expand the emergent light along the second direction of the quantum well mixing inhibition zone
Optical field distribution.
Wherein, the first wave conducting shell and second waveguide layer are respectively to replace shape by the material of at least two different refractivities
Into superlattices laminated construction, the superlattices laminated construction forms the quantum well mixing through quantum well mixing process to be pressed down
Area processed and the quantum well mixing enhancement region, wherein at least two different refractivity in the quantum well mixing inhibition zone
Material severity of mixing up be less than at least two different refractivity in the quantum well mixing enhancement region material it is mixed
Miscellaneous degree.
Wherein, the first wave conducting shell and second waveguide layer are respectively by AlxGa1-xAs and AlyGa1-yTwo kinds of materials of As are handed over
For the superlattices laminated construction of formation;Wherein 0≤x≤1,0≤y≤1, y < x.
Wherein, the epitaxial structure further comprises being set in turn in the first wave conducting shell, quantum well layer and the second wave
It first limiting layer of the laminated construction side of conducting shell, the first N-type covering, third ducting layer and the second N-type covering and sets successively
The second limiting layer of the laminated construction opposite side of the first wave conducting shell, quantum well layer and second waveguide layer and p-type covering are placed in,
Wherein described first limiting layer and the second limiting layer are disposed adjacent respectively with the first wave conducting shell and the second waveguide layer.
Wherein, the refractive index of first limiting layer is identical with the refractive index of second limiting layer, and first limit
Maximum refractive index and minimum folding of the refractive index of preparative layer and the second limiting layer between the material of at least two different refractivity
Penetrate between rate, the refractive index of the third ducting layer between the material of at least two different refractivity maximum refractive index and
Between lowest refractive index, the refractive index of the third ducting layer is more than the refraction of the first N-type covering and the second N-type covering
Rate, first limiting layer, the second limiting layer, the first N-type covering, the second N-type covering and third ducting layer refractive index for pair
Answer the mean refractive index of layer.
Wherein, the third ducting layer, first limiting layer and second limiting layer are respectively by single refractive index
The limitation heterojunction structure respectively that material is formed.
Wherein, the quantum well mixing enhancement region is set close to the Cavity surface of the epitaxial structure, the quantum well mixing suppression
Cavity surface setting of the area processed far from the epitaxial structure.
The present invention provides a kind of manufacturing methods of epitaxial structure, which is characterized in that the manufacturing method includes following step
Suddenly:
Substrate is provided;
First wave conducting shell, quantum well layer and the second waveguide layer of lamination setting along the first direction are formed over the substrate,
Wherein described first wave guide layer and second waveguide layer are respectively the super crystalline substance being alternatively formed by the material of at least two different refractivities
Lattice laminated construction;
Quantum well mixing process is carried out to the superlattices laminated construction, with perpendicular to the of the first direction
The first wave conducting shell and second waveguide layer are divided into quantum well mixing enhancement region on two directions and quantum well mixing inhibits
Area, wherein the severity of mixing up of the material of at least two different refractivity in the quantum well mixing inhibition zone be less than it is described
The severity of mixing up of the material of at least two different refractivity in quantum well mixing enhancement region.
Wherein, the first wave conducting shell for forming the setting of lamination along the first direction over the substrate, quantum well layer and the
Further comprise before the step of two ducting layers:
The second N-type covering, third ducting layer, the first N-type covering and the first limiting layer are sequentially formed over the substrate;
First wave conducting shell, quantum well layer and the second waveguide for forming lamination setting along the first direction over the substrate
Further comprise after the step of layer and before the progress quantum well mixing process to the superlattices laminated construction:
The second limiting layer sequentially formed on the laminated construction of the first wave conducting shell, quantum well layer and second waveguide layer
With p-type covering, wherein first limiting layer and the second limiting layer respectively with the first wave conducting shell and the second waveguide layer
It is disposed adjacent.
Wherein, described the step of carrying out quantum well mixing process to the superlattices laminated construction, includes:
First medium film is covered on the position corresponding to quantum well mixing inhibition zone of the epitaxial structure, and described
Second medium film is covered on the position corresponding to the quantum well mixing enhancement region of epitaxial structure, wherein the first medium film
It can inhibit the quantum well mixing in overlay area below, the second medium film can enhance in overlay area below
Quantum well mixing;
The epitaxial structure of the first medium film and second medium film will be formed under nitrogen protection in annealing furnace
Middle carry out cycle annealing.
The beneficial effects of the invention are as follows:By the way that first wave conducting shell and second waveguide layer are divided into quantum well mixing enhancement region
And quantum well mixing inhibition zone, using the Material property differences of Quantum Well hybrid buildup area and quantum well mixing inhibition zone come
Change optical field distribution, and then realize the control to optical power density, help to improve the reliability and controllability of device.Into one
Step, above structure can also be used for other situations for needing to carry out optical field distribution.
Description of the drawings
Fig. 1 is the structure diagram of epitaxial structure first embodiment of the present invention;
Fig. 2 is superlattices laminated construction of the present invention and corresponding refractive index schematic diagram;
Fig. 3 is the epitaxial structure of second embodiment of the invention and corresponding refractive index schematic diagram;
Fig. 4 is the schematic diagram that laser cavity surface is formed about big light field;
Fig. 5 is the laser near-field distribution schematic diagram of actual computer emulation;
Fig. 6 is the structure diagram that surface deposits two kinds of deielectric-coating of different nature in manufacturing method of the present invention;
Fig. 7 is the structure chart of epitaxial structure obtained after annealing in manufacturing method of the present invention.
Specific embodiment
As shown in Figure 1, the structure diagram of the first embodiment of epitaxial structure of the present invention, epitaxial structures include substrate
1 and Y laminations are set to first wave conducting shell 6, quantum well layer 7 and second waveguide layer 8 on substrate along the first direction, wherein hanging down
Directly on the second direction X of first direction Y, first wave conducting shell 6 and second waveguide layer 7 be divided into quantum well mixing enhancement region and
Quantum well mixing inhibition zone, wherein quantum well mixing enhancement region are used to expand the quantum well mixing enhancement region in a second direction
The optical field distribution of the emergent light of X.
Wherein, first wave conducting shell 6 and second waveguide layer 8 are respectively to be alternatively formed by the material of at least two different refractivities
Superlattices laminated construction, Fig. 2 show superlattices laminated construction and corresponding refractive index schematic diagram.For example, first wave conducting shell 6
It is respectively by Al with second waveguide layer 8xGa1-xAs and AlyGa1-yThe superlattices laminated construction that two kinds of materials of As are alternatively formed;Wherein
0≤x≤1,0≤y≤1, y < x, the thickness of two kinds of alternative materials is respectively several nanometers to several wherein in superlattices laminated construction
Ten nanometers.
Further, this superlattices laminated construction forms quantum well mixing inhibition zone and quantum through quantum well mixing process
The severity of mixing up of at least two different materials in trap hybrid buildup area, wherein quantum well mixing inhibition zone is mixed less than Quantum Well
The severity of mixing up of at least two different materials in miscellaneous enhancement region.In a preferred embodiment, at by quantum well mixing technique
After reason, mixing between the first wave conducting shell 6 and second waveguide layer 8 in quantum well mixing inhibition zone is suppressed so that
The refractive index of the two shows periodic distribution corresponding with original superlattice structure respectively, and inhibits positioned at quantum well mixing
Fully mixed between first wave conducting shell 6 and second waveguide floor 8 in area, the refractive index of the two is caused to reach unanimity.Pass through
Above structure, the optical field distribution of quantum well mixing inhibition zone internal transmission light is relatively small, and in quantum well mixing enhancement region
The optical field distribution of the light of transmission can be then extended.
In addition to above-mentioned composition layer, which further comprises being set in turn in first wave conducting shell 6,7 and of quantum well layer
The first limiting layer 5, the first N-type covering 4, the 3 and second N-type covering 2 of third ducting layer of the laminated construction side of second waveguide layer 8
And it is set in turn in the second limit of the laminated construction opposite side of the first wave conducting shell 6, quantum well layer 7 and second waveguide layer 8
Preparative layer 9 and p-type covering 10, wherein the first limiting layer 5 and the second limiting layer 9 respectively with 8 phase of first wave conducting shell 6 and second waveguide layer
Neighbour's setting.
Wherein the refractive index of the first limiting layer 5 is identical with the refractive index of the second limiting layer 9, and the first limiting layer 5 and second
The refractive index of limiting layer 9 maximum refractive index of the material of at least two different refractivities and minimum in superlattices laminated construction
Between refractive index, the refractive index of third ducting layer 3 material of at least two different refractivities in superlattices laminated construction
Between maximum refractive index and lowest refractive index, the refractive index of third ducting layer 3 is more than the first N-type covering 4 and the second N-type covering 2
Refractive index, the refraction of the first limiting layer 5, the second limiting layer 9, the first N-type covering 4, the second N-type covering 2 and third ducting layer 3
Rate is the mean refractive index of respective layer, and as refractive index curve is to the integration of thickness and the ratio of corresponding layer thickness.
Wherein third ducting layer 3, the first limiting layer 5 and the second limiting layer 9 are respectively what is formed by single refraction materials
Heterojunction structure is limited respectively.Third ducting layer 3 has not only acted as the work for reducing laser beam divergent angle in the epitaxial structure
With, and after being handled by quantum well mixing, the relationship hair between third ducting layer 3 and first wave conducting shell 6 and second waveguide layer 8
Raw to change, first wave conducting shell 6 and second waveguide layer 8 die down, and so as to change the distribution of light field, reduce optical density distribution.Wherein
First limiting layer 5 and the second limiting layer 9 limit in hole and electronics therebetween, therefore the light of hole and the compound generation of electronics
Wave can be effectively limited in the ducting layer being made of first wave conducting shell 6, quantum well layer 7 and second waveguide layer 8, greatly improved
External quantum efficiency.
Second embodiment of the invention is in the case of keeping epitaxial structure constant on the basis of first embodiment, to it
In material component and thickness have been defined specifically.
With reference to Fig. 1, wherein the first wave conducting shell 6 of quantum well mixing inhibition zone and second waveguide layer 8, respectively by 40 periods
Al0.5Ga0.5As/GaAs is alternate to be stacked, wherein individual layer Al0.5Ga0.5The thickness of As is 4nm, and the thickness of individual layer GaAs is
4nm。
Wherein two kinds of materials A l in the first wave conducting shell 6 of quantum well mixing enhancement region and second waveguide layer 80.5Ga0.5As/
The severity of mixing up of GaAs is more than quantum well mixing inhibition zone, and thickness is identical with quantum well mixing inhibition zone respectively, i.e. first wave
Conducting shell 6 and second waveguide layer 8 are 320nm.
Wherein third ducting layer 3 is by Al0.27Ga0.73As is formed, thickness 700nm;
Wherein quantum well layer 7 is by In0.1Ga0.9As is formed, thickness 7nm;
Wherein the first limiting layer 5 and the second limiting layer 9 are by Al0.25Ga0.75As is formed, and thickness is respectively 50nm;
Wherein the first N-type covering 4 and the second N-type covering 2 are by Al0.31Ga0.69As form, thickness be respectively 300nm and
1500nm;
Wherein p-type covering 10 is by Al0.36Ga0.64As is formed, thickness 1500nm.
Fig. 3 is above-mentioned epitaxial structure and its corresponding refractive index schematic diagram;As can be seen from the figure:The refractive index of material with
The component of material and thickness are closely related.
Wherein, it is carried out in quantum well mixing technical process in the epitaxial structure, by the Al in 40 periods0.5Ga0.5As/
GaAs is alternate to be stacked in the superlattices laminated construction first wave conducting shell 6 and second waveguide layer 8 formed, by epitaxial structure upper table
The dielectric insulating film SiO that face is formed2Induction under, Al0.5Ga0.5Al in As thin layers is migrated into GaAs thin layers, GaAs thin layers
In Ga to Al0.5Ga0.5It is migrated in As thin layers, makes two kinds of materials in SiO2The corresponding first wave conducting shell 6 in deielectric-coating overlay area
Mix with being realized in second waveguide layer 8, form quantum well mixing enhancement region.It is situated between correspondingly, being formed in other region upper surfaces
Plasma membrane Si3N4Quantum Well can be inhibited to be mingled in the generation in the region, keep 6 and second wave of first wave conducting shell in epitaxial structure
The superlattices laminated construction of conducting shell 8 does not change, which is quantum well mixing inhibition zone.
Epitaxial structure of the present invention is applicable not only to be adapted to AlGaAs material systems, is also applied for other materials system, packet
Include the material systems such as InGaAsP, InGaAlP, InGaAlAs.
Fourth embodiment of the invention is the concrete application of epitaxial structure of the present invention in the laser.The embodiment is second
Method on the basis of embodiment by quantum well mixing processing is used in close to laser cavity surface region, i.e. quantum well mixing enhancement region
Domain is close to laser cavity surface region.Such as Fig. 4, two kinds of superlattice structure in first wave conducting shell 46 and second waveguide layer 48 are not
A kind of basically identical material of component is changed to material, with the variation of material component, the optical property of material also becomes therewith
Change, this to change the property for changing waveguiding structure, third ducting layer 43 expands the effect of near field optical field distribution in addition, so as to make
The small light field obtained originally becomes big optical field distribution, reduces the optical power density of Cavity surface near zone, reduces damage threshold, reduces
The consume of Cavity surface near zone improves the reliability of device.Fig. 4 is the schematic diagram that laser cavity surface is formed about big light field.
Fig. 5 is the laser near-field distribution schematic diagram of actual computer emulation;From fig. 6 it can be seen that 41 press down for Quantum Well
The corresponding optical power density curve in area processed, i.e. the optical power density curve in other regions of the nonluminal surface in semiconductor laser;
42 be the corresponding optical power density curve in Quantum Well enhancement region, i.e., the optical power density in the Cavity surface region in semiconductor laser is bent
Line;As seen from the figure, in the application example of the semiconductor laser, the peak power density of light reduces 35% or so, effectively
Reduce the consume in Cavity surface region, improve the reliability of device, extend the service life of device.
Embodiment five provides a kind of manufacturing method of the epitaxial structure of semiconductor laser, and manufacturing method includes following
Step:
Substrate 51 is provided;
First wave conducting shell 56, quantum well layer 57 and the second waveguide layer of lamination setting along the first direction are formed on substrate 51
58, wherein first wave conducting shell 56 and second waveguide layer 58 is respectively to be surpassed by what the material of at least two different refractivities was alternatively formed
Lattice laminated construction.Preferably, it is referred to whole before embodiment one sequentially forms progress quantum well mixing on substrate 51
Body epitaxial structure.The second N-type covering 52, third ducting layer 53, the first N-type covering are specially sequentially formed on the substrate 51
54th, the first limitation 55, first wave conducting shell 56, quantum well layer 57, second waveguide layer 58, the second limiting layer 59 and p-type covering 60.
As shown in fig. 6, above-mentioned epitaxial structure after cleaning, according to the design needs, is needing to carry out quantum well mixing
The upper surface in region forms one layer of SiO for enhancing to mix using plasma-reinforced chemical sedimentation2Insulating cap 512, the SiO2
Insulating cap 512 can enhance the component phase counterdiffusion between two kinds of different materials of Quantum Well and potential barrier and superlattices;At it
The upper surface in his region forms one layer and inhibits the Si mixed3N4Insulating cap 511, the Si3N4Insulating cap 511 can be with amount of suppression
Component phase counterdiffusion between two kinds of different materials of sub- trap and potential barrier and superlattices;Thus in SiO2512 lower pairs of insulating cap
The first wave conducting shell 56 and the material character of second waveguide layer 58 answered are changed, and Si3N4It is corresponding under insulating cap 511
The material of first wave conducting shell 56 and second waveguide layer 58 is constant so that SiO2The optical field distribution in the region under insulating cap 512 by
High optical power density originally becomes relatively low conversion efficiency.
The product that upper step is obtained is 800 DEG C in temperature, annealing time is followed under conditions of being 8s under nitrogen protection
Ring is annealed 8 times, obtains epitaxial structure as shown in Figure 7.
To superlattices laminated construction through quantum well mixing process, first wave conducting shell 56 and second waveguide layer 58 are divided
For quantum well mixing enhancement region and quantum well mixing inhibition zone, wherein described at least two in quantum well mixing inhibition zone not
The severity of mixing up of same material is less than the severity of mixing up of at least two different materials in the quantum well mixing inhibition zone.It is logical
It crosses Quantum Well QWI process and changes the property of material in quantum well mixing enhancement region, while keep quantum well mixing inhibition zone
Material structure is constant, and then realizes to the controllable of the optical field distribution of specific region.
In this embodiment, using the quantum well mixing technology (IFVD) of free from admixture vacancy induction to the Cavity surface region of laser
Process is carried out, in addition to the method, Quantum Well immingling technology, impurity diffusion quantum well mixing technology are induced using ion implanting
Etc. processes can be achieved.
The present invention proposes the adjustable epitaxial structure of hot spot and its process implementation method after a kind of epitaxial growth.Wherein epitaxy junction
Structure includes the first wave conducting shell that the superlattice structure that is formed by two kinds of different components forms and second waveguide layer and third waveguide
Layer;From effect, first, which can reduce the angle of divergence of laser beam, reduce scattering loss, reduce threshold
It is worth electric current;Secondly, pass through groups different to two kinds in the superlattice structure in specific region in first wave conducting shell and second waveguide layer
Divide mixing for material, and then regulate and control optical field distribution, realize the control to the optical power density in device and at Cavity surface, improve device
Reliability and controllability, improve external quantum efficiency and electro-optical efficiency;Finally, by reducing the light in device and at Cavity surface
Power density reduces the extent of the destruction of laser lattice, reduces non-radiative recombination and generates a large amount of heat, extends the use of device
Service life.
The foregoing is merely embodiments of the present invention, are not intended to limit the scope of the invention, every to utilize this
The equivalent structure or equivalent flow shift that description of the invention and accompanying drawing content are made directly or indirectly is used in other correlations
Technical field, similarly include in the scope of patent protection of this present invention.