A laser epitaxial wafer with a completely asymmetric structure and a method for preparing the same

Abstract

The present disclosure discloses a laser epitaxial wafer with a completely asymmetric structure and a method for preparing the same. In this epitaxial wafer, the N and P confinement layers have asymmetric component content and thickness; the lower and upper waveguide layers both have gradient component content and asymmetric thickness, and the lower waveguide layer is doped with P atoms; and the lower and upper barrier layers both have gradient component content and asymmetric thickness. In this laser epitaxial wafer with a completely asymmetric structure, the asymmetric component content and thickness of the N and P confinement layers reduce series resistance, minimize heat generation, and shift the light field toward the N side, thereby reducing hole absorption of carriers and improving internal quantum efficiency. Both the lower and upper waveguide layers have gradient component content and asymmetric thickness, enabling controllable optical confinement of the quantum well. The asymmetric thickness and gradient component design of the lower and upper barrier layers improve the reliability of the laser at high temperatures and enhance photoelectric conversion efficiency.

Description

Technical Field

[0001] The present disclosure relates to the technical field of semiconductor lasers, and in particular to a laser epitaxial wafer with a completely asymmetric structure and a preparation method thereof. Background Art

[0002] The information disclosed in the background of the present disclosure is only intended to enhance understanding of the overall background of the present disclosure and should not necessarily be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Semiconductor lasers are widely used in industrial processing, laser communications, medical cosmetology, and other fields due to their advantages such as simple production, small size, and high power. During this period, epitaxial wafers, as the core component of semiconductor lasers, have also experienced rapid development. In recent years, industrial demand for the output power of lasers has become increasingly higher. In order to meet this demand, GaAs-based high-power laser epitaxial wafers generally adopt traditional large optical cavity epitaxial structures, and on this basis, an extreme double asymmetric structure has been developed. Although the extreme double asymmetric structure has the advantages of low series resistance and low carrier leakage, its quantum well confinement factor and gain are both low, which restricts the increase in peak power. It still needs to be improved by optimizing the epitaxial structure. Summary of the Invention

[0004] To address the aforementioned issues, the present disclosure provides a laser epitaxial wafer with a completely asymmetric structure and a method for its preparation. The asymmetric composition and structure of this epitaxial wafer compensate for the shortcomings of an extremely bisymmetric structure, reducing the threshold current, improving reliability at high temperatures, and increasing photoelectric conversion efficiency. To achieve these objectives, the present disclosure provides the following technical solutions.

[0005] The core technology of this disclosure is the completely asymmetric epitaxial wafer structure: the N and P confinement layers have asymmetric composition and thickness, i.e., they have different composition contents and thicknesses. Both the lower and upper waveguide layers exhibit a gradient composition and asymmetric thicknesses, and the lower waveguide layer is doped with P to compensate for stress. Both the lower and upper barrier layers exhibit a gradient composition and asymmetric thicknesses.

[0006] Compared with the prior art, the present disclosure has the following beneficial effects: In the aforementioned fully asymmetric laser epitaxial wafer, the asymmetric composition and thickness of the N- and P-confining layers can reduce series resistance, minimize heat generation, and shift the light field toward the N side, thereby reducing hole absorption of carriers and improving internal quantum efficiency. Both the lower and upper waveguide layers have gradient composition and asymmetric thickness, reducing the band gap between interfaces and lowering voltage, thereby achieving controllable optical confinement in the quantum well. Furthermore, stress is compensated by P doping in the lower waveguide layer, thereby achieving stress neutralization of the entire epitaxial structure and improving reliability. Furthermore, the asymmetric thickness and gradient composition of the lower and upper barrier layers ensure that the thickness of the P-confining layer remains unchanged. This asymmetric thickness of the upper and lower barrier layers improves electron confinement in the quantum well, enhancing the confinement capability of the active region, thereby compensating for the shortcomings of the extremely bisymmetric structure, reducing the threshold current, improving the reliability of the laser at high temperatures, and increasing the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which constitute a part of the present disclosure, are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure.

[0008] Figure 1 This is a schematic diagram of the structure of a laser epitaxial wafer with a completely asymmetric structure in the embodiment of the present disclosure, wherein the numbers represent: 1-substrate, 2-buffer layer, 3-Al x1 Ga 1-x1 AsN confinement layer, 4-Al x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer, 5-Al x3 Ga 1-x3 As lower barrier layer, 6-quantum well layer, 7-Al x4 Ga 1-x4 As upper barrier layer, 8-Al x5 G a1-x5 As upper waveguide layer, 9-Al x6 Ga 1-x6 As P confinement layer, 10-ohm contact layer. DETAILED DESCRIPTION

[0009] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used in the present disclosure have the same meanings as those commonly understood by those skilled in the art to which the present disclosure belongs.

[0010] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit the exemplary embodiments of the present disclosure. For ease of description, if the words "upper," "lower," "left," and "right" appear in this disclosure, they only indicate that they are consistent with the upper, lower, left, and right directions of the drawings themselves, and do not limit the structure. They are merely for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, and operate in a specific orientation. Therefore, they should not be understood as limiting this disclosure.

[0011] On the one hand, a laser epitaxial wafer with a completely asymmetric structure is disclosed, which comprises: a substrate, a buffer layer, an Al x1 Ga 1-x1 AsN confinement layer, Al x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer, Al x3 Ga 1-x3 As lower barrier layer, quantum well layer, Al x4 Ga 1-x4 As upper layer, Al x5 G a1-x5 As upper waveguide layer, Al x6 Ga 1-x6 As P confinement layer, ohmic contact layer. The N confinement layer and the P confinement layer have asymmetric compositions (i.e., x1 ≠ x6) and asymmetric thicknesses. The lower waveguide layer and the upper waveguide layer have asymmetric thicknesses, and x2 in the lower waveguide layer gradually decreases from the lower layer to the upper layer, while x5 in the upper waveguide layer gradually decreases from the upper layer to the lower layer. Furthermore, the lower waveguide layer is doped with P atoms. The lower barrier layer and the upper barrier layer have asymmetric thicknesses, and x3 in the lower barrier layer gradually decreases from the lower layer to the upper layer, while x4 in the upper barrier layer gradually decreases from the upper layer to the lower layer, indicating a gradual symmetry in composition.

[0012] In some typical embodiments of the present disclosure, in the N confinement layer, 0.3≤x1≤0.6; in the P confinement layer, 0.5≤x6≤0.9.

[0013] In some typical embodiments of the present disclosure, the thickness of the N confinement layer is 2-3 um, and the thickness of the P confinement layer is 0.5-1 um.

[0014] In some typical embodiments of the present disclosure, x4 in the upper barrier layer gradually decreases from the upper layer to the lower layer to the value of x3 in the uppermost layer of the lower barrier layer. Preferably, 0.1≤x3≤0.4, 0.1≤x4≤0.4.

[0015] In some typical embodiments of the present disclosure, x5 in the upper waveguide layer gradually decreases from the upper layer to the lower layer to the value of x2 in the uppermost layer of the lower waveguide layer. Preferably, 0.3≤x2≤0.4, 0.3≤x5≤0.8, 0.95≤y1≤0.99.

[0016] In some typical embodiments of the present disclosure, the thickness of the lower waveguide layer is 800-1500 nm, and the thickness of the upper waveguide layer is 100-200 nm.

[0017] In some typical embodiments of the present disclosure, the thickness of the lower barrier layer is 100-300 nm, the thickness of the upper barrier layer is 50-100 nm, and in the same epitaxial wafer, the thickness of the lower barrier layer and the upper barrier layer are different to achieve an asymmetric thickness structural design.

[0018] In some typical embodiments of the present disclosure, the material of the quantum well layer includes In z1 Ga 1-z1 Any one of As, AlGaInP, etc. Optionally, the value of z1 in the quantum well layer is 0.1-0.2.

[0019] In some typical embodiments of the present disclosure, the material of the substrate includes any one of GaAs, sapphire, SiC, etc.

[0020] In some typical embodiments of the present disclosure, the material of the buffer layer includes any one of GaAs, InP, GaN, etc. Optionally, the thickness of the buffer layer is 100-300 nm.

[0021] In some typical embodiments of the present disclosure, the material of the quantum well layer includes In z1 Ga 1-z1 Any one of As, AlGaInP, etc. Optionally, the value of z1 is between 0.1 and 0.2.

[0022] In some typical embodiments of the present disclosure, the material of the ohmic contact layer includes any one of GaAs, GaN, GaP, etc. Optionally, the thickness of the ohmic contact layer is 100-300 nm.

[0023] In some typical embodiments of the present disclosure, the N side (buffer layer, N confinement layer, lower waveguide layer) is doped with silicon atoms, and the P side (upper waveguide layer, P confinement layer, ohmic contact layer) is doped with a carbon source.

[0024] Furthermore, the buffer layer is doped with silicon atoms; optionally, the doping concentration is 1E18 to 3E18 atoms / cm 3 .

[0025] Furthermore, the N confinement layer is doped with silicon atoms. Optionally, the doping concentration is 5E17 to 2E18 atoms / cm 3 .

[0026] Furthermore, the lower waveguide layer is doped with silicon atoms. Optionally, the doping concentration is 5E17 to 2E18 atoms / cm 3 .

[0027] Furthermore, the upper waveguide layer is doped with carbon atoms. Optionally, the doping concentration is 5E17-2E18 atoms / cm 3 .

[0028] Furthermore, the P confinement layer is doped with carbon atoms. Optionally, the doping concentration is 1E17 to 5E18 atoms / cm 3 .

[0029] Furthermore, the ohmic contact layer is doped with carbon atoms. Optionally, the doping concentration is 9E18 to 5E19 atoms / cm 3 .

[0030] In the above typical embodiment, the purpose of N-side doping is to provide electrons, and through the change of doping gradient (from N confinement layer to lower barrier layer: Si doping becomes lower and lower until no doping, forming a doping gradient from high to low), a potential difference is achieved that is conducive to the migration of electrons to the quantum well. The purpose of P-side doping is to provide holes, and through the change of doping gradient (from upper barrier layer to P confinement layer: C doping becomes higher and higher from no doping in the upper barrier layer, forming a doping gradient from low to high), a potential difference is achieved that is conducive to the migration of holes to the quantum well, and finally the holes and electrons are recombinated in the quantum well.

[0031] On the other hand, a method for preparing the laser epitaxial wafer with a completely asymmetric structure is disclosed, comprising the following steps:

[0032] (1) Heat treatment of the substrate in a reducing atmosphere to remove surface water and oxygen.

[0033] (2) Growing a buffer layer on the substrate.

[0034] (3) Growing Al on the buffer layer x1 Ga 1-x1 As N limiting layer.

[0035] (4) Growing Al on the N confinement layer x2 Ga 1-x2 As y1 P 1-y1 The lower waveguide layer is formed, and the value of x2 is gradually decreased upward from the lower layer of the lower waveguide layer by linearly changing the amount of Al and Ga introduced with the growth time.

[0036] (5) Growing Al on the lower waveguide layer x3 Ga 1-x3 As lower barrier layer, and the value of x3 is gradually reduced from the lower layer of the lower waveguide layer upward by linearly changing the amount of Al and Ga introduced with the growth time.

[0037] (6) Growing a quantum well layer on the lower barrier layer.

[0038] (7) Growing Al on the quantum well layer x4 Ga 1-x4 As upper barrier layer, and the value of x4 is gradually increased upward from the lower layer of the upper barrier layer by linearly changing the amount of Al and Ga introduced with the growth time.

[0039] (8) Growing Al on the upper barrier layer x5 G a1-x5 As upper waveguide layer, and the value of x5 is gradually increased upward from the lower layer of the upper waveguide layer by linearly changing the amount of Al and Ga introduced with the growth time.

[0040] (9) Growing Al on the upper waveguide layer x6 Ga 1-x6 As P confinement layer, and x1≠x6.

[0041] (10) An ohmic contact layer is grown on the P confinement layer.

[0042] In some typical embodiments of the present disclosure, the above steps (2), (3), and (4) further include the step of doping silicon atoms during the preparation of the buffer layer, the N confinement layer, and the lower waveguide layer.

[0043] In some typical embodiments of the present disclosure, the above steps (8), (9), and (10) further include the step of doping carbon atoms during the preparation of the upper waveguide layer, the P confinement layer, and the ohmic contact layer.

[0044] In some typical embodiments of the present disclosure, the temperature of the heat treatment in the above step (1) is 740-780°C, the growth temperature of step (2) is 720-740°C, the growth temperature of steps (3) to (9) is 640-680°C, and the growth temperature of step (10) is 540-560°C.

[0045] The technical solution of the present disclosure is now further described with reference to the accompanying drawings and specific embodiments.

[0046] Example 1

[0047] A method for preparing a laser epitaxial wafer with a completely asymmetric structure comprises the following steps:

[0048] (1) Place the GaAs substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 780°C and bake for 10 minutes, then introduce AsH3 to heat-treat the GaAs substrate 1 to remove water and oxygen on the substrate surface.

[0049] (2) When the temperature of the reaction chamber drops to 730°C, TMGa and AsH3 (molar ratio: 1:100) are introduced to grow a GaAs buffer layer 2 with a thickness of 300 nm on the GaAs substrate 1, and silicon is doped with Si2H6 as a doping source at a doping concentration of 2E18 atoms / cm 3 .

[0050] (3) When the temperature of the reaction chamber drops to 680°C, TMAl, TMGa and AsH3 are introduced (the molar ratio of TMAl to TMGa is 7:13; the molar ratio of TMAl+TMGa to AsH3 is 1:100), and an Al2O3 layer with a thickness of 2.5 μm is grown on the GaAs buffer layer 2. 0.35 Ga 0.65 As N confines the layer 3, and Si2H6 is used as the doping source for silicon doping with a doping concentration of 1E18 atoms / cm 3 .

[0051] (4) Maintaining the temperature at 680°C, introducing TMAl, TMGa, AsH3 and PH3, 0.35 Ga 0.65 A 0.9 μm thick Al layer is grown on the AsN confinement layer 3. x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer 4; wherein, as the lower waveguide layer 4 grows, y1 = 0.96, and the amount of Al and Ga introduced changes linearly with the growth time to make x2 gradually change from 0.35 to 0.30, and Si2H6 is used as the doping source for silicon doping, and the doping concentration is 7E17 atoms / cm 3 .

[0052] (5) Maintaining the temperature at 680°C, introducing TMAl, TMGa and AsH3, and growing Al with a thickness of 150 nm on the lower waveguide layer 4 x3 Ga 1-x3 As lower barrier layer 5. As the lower barrier layer 5 grows, x3 gradually changes from 0.30 to 0.2 by linearly changing the amount of Al and Ga introduced with the growth time.

[0053] (6) When the temperature of the reaction chamber drops to 660°C, TMIn, TMGa and AsH3 are introduced, and In with a thickness of 7 nm continues to grow on the lower barrier layer 5. 0.15Ga 0.85 As quantum well layer 6.

[0054] (7) When the temperature of the reaction chamber drops to 680°C, TMAl, TMGa and AsH3 are introduced, and Al with a thickness of 80 nm is grown on the quantum well layer 6. x4 Ga 1-x 4As upper barrier layer 7. As the upper barrier layer 7 grows, x4 gradually changes from 0.2 to 0.3 by linearly changing the amount of Al and Ga introduced with the growth time.

[0055] (8) Maintaining the temperature at 680°C, continue to introduce TMAl, TMGa and AsH3 to grow Al with a thickness of 150nm on the upper barrier layer 7. x5 Ga 1-x5 As upper waveguide layer 8. As the upper waveguide layer 8 grows, the amount of Al and Ga introduced changes linearly with the growth time, so that x5 gradually changes from 0.3 to 0.6. At the same time, carbon doping is performed using CBr4 as a doping source, with a doping concentration of 7E17 atoms / cm 3 .

[0056] (9) Maintaining the temperature at 680°C, continue to introduce TMAl, TMGa and AsH3 to grow Al with a thickness of 0.8 μm on the upper waveguide layer 8. 0.6 Ga 0.4 AsP limiting layer 9. At the same time, carbon doping is performed using CBr4 as the doping source, with a doping concentration of 2E18 atoms / cm 3 .

[0057] (10) When the reaction chamber temperature drops to 550°C, TMGa and AsH3 are introduced, and a GaAs ohmic contact layer 10 with a thickness of 300 nm is grown on the P confinement layer 9. At the same time, carbon doping is performed using CBr4 as a doping source, with a doping concentration of 5E19 atoms / cm 3 , that is, the laser epitaxial wafer with a completely asymmetric structure is obtained, and its structural schematic diagram is referenced Figure 1 .

[0058] Example 2

[0059] A method for preparing a laser epitaxial wafer with a completely asymmetric structure comprises the following steps:

[0060] A method for preparing a laser epitaxial wafer with a completely asymmetric structure comprises the following steps:

[0061] (1) Place the GaAs substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 740°C and bake for 10 minutes, then introduce AsH3 to heat-treat the GaAs substrate 1 to remove water and oxygen on the substrate surface.

[0062] (2) When the temperature of the reaction chamber drops to 720°C, TMGa and AsH3 (molar ratio: 1:100) are introduced to grow a GaAs buffer layer 2 with a thickness of 100 nm on the GaAs substrate 1, and silicon is doped with Si2H6 as a doping source at a doping concentration of 1E18 atoms / cm 3 .

[0063] (3) When the temperature of the reaction chamber drops to 640°C, TMAl, TMGa and AsH3 are introduced (the molar ratio of TMAl to TMGa is 3:7; the molar ratio of TMAl+TMGa to AsH3 is 1:100), and an Al2O3 layer with a thickness of 2 μm is grown on the GaAs buffer layer 2. 0.30 Ga 0.70 As N confines the layer 3, and Si2H6 is used as the doping source for silicon doping with a doping concentration of 5E17 atoms / cm 3 .

[0064] (4) Maintaining the temperature at 640°C, introducing TMAl, TMGa, AsH3 and PH3, 0.35 Ga 0.65 A 0.8 μm thick Al layer is grown on the AsN confinement layer 3. x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer 4; wherein, as the lower waveguide layer 4 grows, x2 gradually changes from 0.35 to 0.30 by linearly changing the amount of Al and Ga introduced with the growth time, and y1 = 0.95, and Si2H6 is used as a doping source for silicon doping, with a doping concentration of 7E17 atoms / cm 3 .

[0065] (5) Maintaining the temperature at 640°C, introducing TMAl, TMGa and AsH3, and growing Al with a thickness of 100 nm on the lower waveguide layer 4. x3 Ga 1-x3 As lower barrier layer 5. As the lower barrier layer 5 grows, x3 is gradually changed from 0.30 to 0.2 by linearly changing the amount of Al and Ga introduced with the growth time.

[0066] (6) When the temperature of the reaction chamber drops to 640°C, TMIn, TMGa and AsH3 are introduced, and In with a thickness of 5 nm continues to grow on the lower barrier layer 5. 0.10 Ga 0.90 As quantum well layer 6.

[0067] (7) When the temperature of the reaction chamber drops to 640°C, TMAl, TMGa and AsH3 are introduced, and Al with a thickness of 50 nm is grown on the quantum well layer 6. x4 Ga 1-x 4As upper barrier layer 7. As the upper barrier layer 7 grows, x4 is gradually changed from 0.2 to 0.3 by linearly changing the amount of Al and Ga introduced with the growth time.

[0068] (8) Maintaining the temperature at 640°C, continue to introduce TMAl, TMGa and AsH3 to grow Al with a thickness of 100 nm on the upper barrier layer 7. x5 Ga 1-x5 As upper waveguide layer 8. As the upper waveguide layer 8 grows, x5 gradually changes from 0.3 to 0.6 by linearly changing the amount of Al and Ga introduced with the growth time. At the same time, carbon doping is performed using CBr4 as a doping source with a doping concentration of 5E17 atoms / cm 3 .

[0069] (9) Maintaining the temperature at 640°C, continue to introduce TMAl, TMGa and AsH3 to grow Al with a thickness of 0.5 μm on the upper waveguide layer 8. 0.5 Ga 0.5 AsP limiting layer 9. At the same time, carbon doping is performed using CBr4 as the doping source, with a doping concentration of 1E17 atoms / cm 3 .

[0070] (10) When the reaction chamber temperature drops to 540°C, TMGa and AsH3 are introduced, and a GaAs ohmic contact layer 10 with a thickness of 100 nm is grown on the P confinement layer 9. At the same time, carbon doping is performed using CBr4 as a doping source, with a doping concentration of 9E18 atoms / cm 3 , thus obtaining the laser epitaxial wafer with a completely asymmetric structure.

[0071] Example 3

[0072] A method for preparing a laser epitaxial wafer with a completely asymmetric structure comprises the following steps:

[0073] A method for preparing a laser epitaxial wafer with a completely asymmetric structure comprises the following steps:

[0074] (1) Place the GaAs substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 780°C and bake for 10 minutes, then introduce AsH3 to heat-treat the GaAs substrate 1 to remove water and oxygen on the substrate surface.

[0075] (2) When the temperature of the reaction chamber drops to 740°C, TMGa and AsH3 (molar ratio: 1:100) are introduced to grow a GaAs buffer layer 2 with a thickness of 300 nm on the GaAs substrate 1, and silicon is doped with Si2H6 as a doping source at a doping concentration of 3E18 atoms / cm 3 .

[0076] (3) When the temperature of the reaction chamber drops to 680°C, TMAl, TMGa and AsH3 are introduced (the molar ratio of TMAl to TMGa is 3:2; the molar ratio of TMAl+TMGa to AsH3 is 1:100), and an Al2O3 layer with a thickness of 3 μm is grown on the GaAs buffer layer 2. 0.60 Ga 0.40 As N confines the layer 3, and Si2H6 is used as the doping source for silicon doping with a doping concentration of 2E18 atoms / cm 3 .

[0077] (4) Maintaining the temperature at 680°C, introducing TMAl, TMGa, AsH3 and PH3, 0.35 Ga 0.65 A 1.5 μm thick Al layer is grown on the AsN confinement layer 3. x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer 4; wherein, as the lower waveguide layer 4 grows, x2 gradually changes from 0.35 to 0.30 by linearly changing the amount of Al and Ga introduced with the growth time. y1 = 0.99, and Si2H6 is used as a doping source for silicon doping, with a doping concentration of 2E18 atoms / cm 3 .

[0078] (5) Maintaining the temperature at 680°C, introducing TMAl, TMGa and AsH3, and growing Al with a thickness of 300 nm on the lower waveguide layer 4. x3 Ga 1-x3 As lower barrier layer 5. As the lower barrier layer 5 grows, x3 is gradually changed from 0.30 to 0.2 by linearly changing the amount of Al and Ga introduced with the growth time.

[0079] (6) When the temperature of the reaction chamber drops to 680°C, TMIn, TMGa and AsH3 are introduced, and In with a thickness of 10 nm continues to grow on the lower barrier layer 5. 0.20 Ga 0.80 As quantum well layer 6.

[0080] (7) When the temperature of the reaction chamber drops to 680°C, TMAl, TMGa and AsH3 are introduced, and Al with a thickness of 100 nm is grown on the quantum well layer 6. x4Ga 1-x 4As upper barrier layer 7. As the upper barrier layer 7 grows, x4 is gradually changed from 0.2 to 0.3 by linearly changing the amount of Al and Ga introduced with the growth time.

[0081] (8) Maintaining the temperature at 680°C, continue to introduce TMAl, TMGa and AsH3 to grow Al with a thickness of 200 nm on the upper barrier layer 7. x5 Ga 1-x5 As upper waveguide layer 8. As the upper waveguide layer 8 grows, x5 gradually changes from 0.3 to 0.6 by linearly changing the amount of Al and Ga introduced with the growth time. At the same time, carbon doping is performed using CBr4 as a doping source with a doping concentration of 1E18 atoms / cm 3 .

[0082] (9) Maintaining the temperature at 680°C, continue to introduce TMAl, TMGa and AsH3 to grow Al with a thickness of 1.0 μm on the upper waveguide layer 8. 0.9 Ga 0.1 AsP limiting layer 9. At the same time, carbon doping is performed using CBr4 as the doping source, with a doping concentration of 5E18 atoms / cm 3 .

[0083] (10) When the reaction chamber temperature drops to 560°C, TMGa and AsH3 are introduced, and a GaAs ohmic contact layer 10 with a thickness of 300 nm is grown on the P confinement layer 9. At the same time, carbon doping is performed using CBr4 as a doping source, with a doping concentration of 5E19 atoms / cm 3 , thus obtaining the laser epitaxial wafer with a completely asymmetric structure.

[0084] Comparative Example 1:

[0085] A method for preparing a laser epitaxial wafer with a symmetrical structure, wherein the preparation process is the same as that of Example 1, except that: the lower waveguide layer 4 is Al x2 Ga 1-x2 As, and x2=0.3. The upper waveguide layer 8 is Al x5 Ga 1-x5 As, and x5=0.3. The lower barrier layer 5 is Al x3 Ga 1-x3 As, and x3 = 0.2. The upper barrier layer 7 is made of Al x4 Ga 1-x4 As, and x4=0.2. That is, the waveguide layer and the barrier layer of this embodiment do not adopt the form of composition gradient, and the lower waveguide layer 4 is not doped with P atoms.

[0086] Comparative Example 2:

[0087] A method for preparing a laser epitaxial wafer, wherein the preparation process is the same as that of embodiment 1, except that: the lower waveguide layer 4 is not doped with P.

[0088] Comparative Example 3:

[0089] A method for preparing a laser epitaxial wafer with a symmetrical structure, wherein the preparation process is the same as that of Example 1, except that the upper barrier layer 7 is Al x4 Ga 1-x4 As, and x4 = 0.2. The lower barrier layer 5 is Al x3 Ga 1-x3 As, and x3=0.2, that is, the upper and lower barrier layers do not present the design feature of gradual composition change.

[0090] Comparative Example 4:

[0091] A method for preparing a laser epitaxial wafer with a symmetrical structure, wherein the preparation process is the same as that of Example 1, except that: the lower waveguide layer 4 is Al x2 Ga 1-x2 As, and x2 = 0.3. The upper waveguide layer 8 is Al x5 Ga 1-x 5As, and x5=0.3, that is, the upper and lower waveguide layers present a design feature of gradual composition change.

[0092] The epitaxial wafers prepared in the above embodiments and comparative examples were respectively packaged onto COS heat sinks. The samples were tested at room temperature under a continuous operating current of 25A. Fifteen COS wafers of each sample were selected for continuous aging test at 30A to monitor the number of failures. The results are shown in Table 1.

[0093] Threshold current Output power Operating voltage Number of aging failures Aging time Example 1 1.53A 27.46W 1.62V 0 1000h Example 2 1.60A 26.24W 1.65V 0 1000h Example 3 1.55A 25.93W 1.63V 0 1000h Comparative Example 1 1.68A 25.06W 1.71V 2 1000 Comparative Example 2 1.66A 25.12W 1.78V 5 1000 Comparative Example 3 1.63A 24.85W 1.73V 2 1000 Comparative Example 4 1.62A 25.22W 1.70V 3 1000

[0094] The results in Table 1 show that the embodiment has significantly lower threshold current, operating voltage, and number of aging failures, as well as higher output power. This is because the embodiment adopts asymmetric composition and thickness between the N-limiting layer and the P-limiting layer to reduce series resistance, reduce heat generation, shift the light field toward the N side, reduce hole absorption of carriers, and improve internal quantum efficiency; the waveguide layer and the upper waveguide layer adopt gradient composition and asymmetric thickness, which reduces the band gap between the interfaces, reduces voltage, and realizes controllable optical confinement of the quantum well. In addition, the doping of P in the lower waveguide layer achieves stress neutralization of the entire epitaxial structure, thereby improving reliability; the asymmetric thickness and gradient composition between the lower barrier layer and the upper barrier layer compensate for the shortcomings of the extremely bisymmetric structure, reduce the threshold current, improve reliability at high temperatures, and improve photoelectric conversion efficiency.

[0095] Finally, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this disclosure shall be included within the scope of protection of this disclosure. Although the above description of the specific embodiments of the present disclosure is combined with the accompanying drawings, it is not intended to limit the scope of protection of this disclosure. Those skilled in the art should understand that based on the technical solution of this disclosure, various modifications or variations that can be made by those skilled in the art without expending creative effort are still within the scope of protection of this disclosure.

Claims

1. A laser epitaxial wafer with a completely asymmetric structure, characterized in that: In this epitaxial wafer: the N limiting layer and the P limiting layer have asymmetric composition and thickness; Al x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer, Al x5 G a1-x5 The As upper waveguide layer has an asymmetric thickness, and x2 in the lower waveguide layer decreases gradually from the lower layer to the upper layer, and x5 in the upper waveguide layer decreases gradually from the upper layer to the lower layer, and the lower waveguide layer is doped with P atoms; Al x3 Ga 1-x3 As lower barrier layer, Al x4 Ga 1-x4 The As upper barrier layers all have an asymmetric thickness characteristic, and x3 in the lower barrier layer gradually decreases from the lower layer to the upper layer, and x4 in the upper barrier layer gradually decreases from the upper layer to the lower layer.

2. The laser epitaxial wafer with a completely asymmetric structure according to claim 1, characterized in that: It includes the following: substrate, buffer layer, Al x1 Ga 1-x1 AsN confinement layer, Al x2 Ga 1-x2 As y1 P 1-y1 Lower waveguide layer, Al x3 Ga 1-x3 As lower barrier layer, quantum well layer, Al x4 Ga 1-x4 As upper layer, Al x5 G a1-x5 As upper waveguide layer, Al x6 Ga 1-x6 As P confinement layer, ohmic contact layer; wherein: the components of the N confinement layer and the P confinement layer are asymmetric, that is, x1≠x6.

3. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: In the N restriction layer, 0.3≤x1≤0.6; in the P restriction layer, 0.5≤x6≤0.

9.

4. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The thickness of the N restriction layer is 2-3 μm, and the thickness of the P restriction layer is 0.5-1 μm.

5. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: In the upper barrier layer, x4 gradually decreases from the upper layer to the lower layer to reach the value of x3 in the uppermost layer of the lower barrier layer.

6. The laser epitaxial wafer with a completely asymmetric structure according to claim 5, characterized in that: 0.1≤x3≤0.4, 0.1≤x4≤0.

4.

7. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: In the upper waveguide layer, x5 gradually decreases from the upper layer to the lower layer to reach the value of x2 in the uppermost layer of the lower waveguide layer.

8. The laser epitaxial wafer with a completely asymmetric structure according to claim 7, characterized in that: 0.3≤x2≤0.4, 0.3≤x5≤0.8, 0.95≤y1≤0.

99.

9. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The thickness of the lower waveguide layer is 800-1500 nm, and the thickness of the upper waveguide layer is 100-200 nm.

10. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The thickness of the lower barrier layer is 100-300 nm, and the thickness of the upper barrier layer is 50-100 nm. In the same epitaxial wafer, the thickness of the lower barrier layer and the thickness of the upper barrier layer are different.

11. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The material of the quantum well layer includes In z1 Ga 1-z1 Any one of As and AlGaInP.

12. The laser epitaxial wafer with a completely asymmetric structure according to claim 11, characterized in that: The value of z1 in the quantum well layer is 0.1-0.

2.

13. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The material of the substrate includes any one of GaAs, sapphire, and SiC.

14. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The material of the buffer layer includes any one of GaAs, InP, and GaN.

15. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The thickness of the buffer layer is 100-300 nm.

16. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The material of the quantum well layer includes In z1 Ga 1-z1 Any one of As and AlGaInP.

17. The laser epitaxial wafer with a completely asymmetric structure according to claim 16, characterized in that: The value of z1 is between 0.1 and 0.

2.

18. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The material of the ohmic contact layer includes any one of GaAs, GaN, and GaP.

19. The laser epitaxial wafer with a completely asymmetric structure according to claim 2, characterized in that: The thickness of the ohmic contact layer is 100-300 nm.

20. The laser epitaxial wafer with a completely asymmetric structure according to any one of claims 2 to 19, characterized in that: The N side is doped with silicon atoms, and the P side is doped with a carbon source; wherein the N side includes: a buffer layer, an N confinement layer, and a lower waveguide layer, and the P side includes an upper waveguide layer, a P confinement layer, and an ohmic contact layer.

21. The laser epitaxial wafer with a completely asymmetric structure according to claim 20, characterized in that: The buffer layer is doped with silicon atoms.

22. The laser epitaxial wafer with a completely asymmetric structure according to claim 21, characterized in that: Doping concentration is 1E18~3E18 atoms / cm 3 .

23. The laser epitaxial wafer with a completely asymmetric structure according to claim 22, characterized in that: Doping concentration is 5E17~2E18 atoms / cm 3 .

24. The laser epitaxial wafer with a completely asymmetric structure according to claim 20, characterized in that: The lower waveguide layer is doped with silicon atoms.

25. The laser epitaxial wafer with a completely asymmetric structure according to claim 24, characterized in that: Doping concentration is 5E17~2E18 atoms / cm 3 .

26. The laser epitaxial wafer with a completely asymmetric structure according to claim 20, characterized in that: The upper waveguide layer is doped with carbon atoms.

27. The laser epitaxial wafer with a completely asymmetric structure according to claim 26, characterized in that: Doping concentration is 5E17-2E18 atoms / cm 3 .

28. The laser epitaxial wafer with a completely asymmetric structure according to claim 20, characterized in that: The P confinement layer is doped with carbon atoms.

29. The laser epitaxial wafer with a completely asymmetric structure according to claim 28, characterized in that: Doping concentration is 1E17~5E18 atoms / cm 3 .

30. The laser epitaxial wafer with a completely asymmetric structure according to claim 20, characterized in that: The ohmic contact layer is doped with carbon atoms.

31. The laser epitaxial wafer with a completely asymmetric structure according to claim 30, characterized in that: Doping concentration is 9E18~5E19 atoms / cm 3 .

32. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to any one of claims 1 to 31, characterized in that: The steps include: (1) Heat treatment of the substrate in a reducing atmosphere to remove surface water and oxygen; (2) growing a buffer layer on the substrate; (3) Growing Al on the buffer layer x1 Ga 1-x1 As N limiting layer; (4) Growing Al on the N confinement layer x2 Ga 1-x2 As y1 P 1-y1 a lower waveguide layer, and causing the value of x2 to decrease gradually upward from the lower layer of the lower waveguide layer; (5) Growing Al on the lower waveguide layer x3 Ga 1-x3 As lower barrier layer, and the value of x3 is gradually decreased from the lower layer of the lower waveguide layer upward; (6) growing a quantum well layer on the lower barrier layer; (7) Growing Al on the quantum well layer x4 Ga 1-x4 As is an upper layer, and the value of x4 is gradually increased from the lower layer of the upper layer upward; (8) Growing Al on the upper barrier layer x5 G a1-x5 As upper waveguide layer, and making the value of x5 gradually increase upward from the lower layer of the upper waveguide layer; (9) Growing Al on the upper waveguide layer x6 Ga 1-x6 As P confinement layer, and x1≠x6; (10) An ohmic contact layer is grown on the P confinement layer.

33. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to claim 32, characterized in that: Said (2), (3) and (4) also include the step of doping silicon atoms during the preparation of said buffer layer, N limiting layer and lower waveguide layer.

34. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to claim 32, characterized in that: Said (8), (9) and (10) also include the step of doping carbon atoms during the preparation process of said upper waveguide layer, P confinement layer and ohmic contact layer.

35. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to claim 32, characterized in that: The temperature of the heat treatment in (1) is 740-780°C.

36. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to claim 32, characterized in that: The growth temperature of (2) is 720-740°C.

37. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to claim 32, characterized in that: The growth temperature of (3) to (9) is 640 to 680°C.

38. The method for preparing a laser epitaxial wafer with a completely asymmetric structure according to claim 32, characterized in that: The growth temperature of (10) is 540~560℃.

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