A GaN-based laser and its preparation method

Abstract

The present invention relates to a laser, which comprises at least a quantum well active region and a lower waveguide layer, wherein a stress release layer is arranged between the quantum well active region and the lower waveguide layer, and the quantum well active region has a three-dimensional morphology. The laser adds a stress release structure before the growth of the quantum well active region, thereby reducing the mismatch stress when growing the quantum well active region, reducing the crystal defects and polarization electric field in the active region, thereby weakening the QCSE, increasing the overlap of the electron-hole wave function, and being conducive to improving the radiation recombination efficiency of the GaN-based laser, increasing its limitation factor, and achieving the effect of improving the performance such as power. The preparation method is simple to operate, has good process repeatability, and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the field of lasers, and relates to a laser and a preparation method thereof, and in particular to a GaN-based laser and a preparation method thereof. Background Art

[0002] Gallium nitride-based lasers are a current research hotspot. As a new generation of optoelectronic devices, they have received widespread attention and application in new display, optical communication, and light illumination. Gallium nitride lasers need to work at high current density and have very high requirements for the crystal quality of the material. Unlike other gallium nitride devices, such as LEDs, which are not very sensitive to crystal quality, poor material quality will directly affect the life and output power of the laser for lasers. Existing epitaxial structures and methods are still far from the life and performance of other lasers (GaAs-based).

[0003] Among them, it is very difficult to grow a light-emitting active region of an InGaN / GaN quantum well structure with high crystal quality and high efficiency. The main reasons are: the lattice mismatch between InGaN and GaN is very large, which is even more serious in the green light band with high In content. The large lattice mismatch will produce large mismatch stress and high-density defects, reducing the crystal quality, and thus affecting the performance and reliability of the device. Furthermore, the polarization effect of the InGaN / GaN quantum well active region leads to an ultra-high polarization electric field, such as Figure 3 As shown, the radiation efficiency is sharply reduced. Summary of the invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a GaN-based laser and a preparation method thereof, wherein the GaN-based laser adds a stress release structure before the growth of the quantum well active region, thereby reducing the mismatch stress when growing the quantum well active region, reducing the crystal defects and polarization electric field in the active region, thereby weakening the QCSE, increasing the electron-hole wave function overlap, and being conducive to improving the radiation recombination efficiency of the GaN-based laser, increasing its limitation factor, and achieving the effect of improving performance such as power. The preparation method is simple to operate, has good process repeatability, and is suitable for industrial production.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] One of the purposes of the present invention is to provide a laser, which comprises at least a quantum well active region and a lower waveguide layer, wherein a stress release layer is arranged between the quantum well active region and the lower waveguide layer, and the quantum well active region has a three-dimensional morphology.

[0007] In the present invention, by adding a stress release layer, the bias stress inside the film before the stress release layer is grown is converted into a tensile stress, so that the polarization effect caused by the bias stress is reduced, thereby greatly weakening the energy band tilt and the QCSE; when the quantum well active region is subsequently grown, the material interface fluctuations (such as Figure 5 As shown in the figure, the tensile stress causes the quantum well active region to form a three-dimensional morphology, which absorbs more In components. The increase in the In incorporation rate increases the growth temperature of the quantum well active region, which directly improves the crystal quality and effectively reduces the half-width height of the luminescence spectrum, the gain of the lasing, and the concentration of the laser spot.

[0008] In the present invention, by improving the growth morphology, interface and crystal quality of the quantum well active region, the stress release and the relaxed three-dimensional quantum well band reduce the effects of piezoelectric polarization and spontaneous polarization, so that the energy band tilt is greatly weakened, such as Figure 4 Finally, when electrons and holes are injected, the wave function overlap increases, which again improves the radiative recombination efficiency and the final laser lasing gain.

[0009] As a preferred technical solution of the present invention, the stress release layer is an InGaN / GaN superlattice structure layer, an InGaN single layer or a GaN single layer.

[0010] As a preferred technical solution of the present invention, when the stress release layer is an InGaN / GaN superlattice structure layer or an InGaN single layer, the In element content of the stress release layer is greater than the In element content of the quantum well active region.

[0011] Preferably, the lower waveguide layer is an InGaN waveguide layer.

[0012] Preferably, the In element content of the quantum well active region is greater than the In element content of the InGaN waveguide layer.

[0013] In the present invention, a stress release layer having an In element content greater than that of the quantum well active region is provided between the quantum well active region and the lower waveguide layer. The larger indium component can accelerate the release of the mismatch stress, so that the internal portion of the film changes from a bias stress state to a tensile stress state.

[0014] Preferably, the In content of the stress release layer is 15% to 25%, and the In content of the quantum well active region is 10% to 20%. The In content of the stress release layer can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25%, and the In content of the quantum well active region can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0015] As a preferred technical solution of the present invention, the total thickness of the InGaN single layer or GaN single layer is 5 to 50 nm, such as 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, and the thickness of the InGaN layer and the GaN layer in the InGaN / GaN superlattice structure layer are independently 1 to 5 nm, such as 1 nm, 2 nm, 3 nm, 4 nm or 5 nm, but are not limited to the listed values, and other unlisted values ​​within the above numerical ranges are equally applicable.

[0016] As a preferred technical solution of the present invention, when the stress release layer is a GaN single layer, the GaN single layer at least includes a porous structure or supersaturated Ga atoms.

[0017] In the present invention, by arranging a GaN monolayer with a porous structure between the quantum well active region and the lower waveguide layer, stress relaxation can be performed for the subsequent growth of the quantum well active region; in the GaN monolayer with an oversaturated Ga element content, the oversaturated Ga atoms enter the GaN layer to occupy the N position, and since the Ga atomic radius is greater than the N atomic radius, the bias stress is converted into a tensile stress inside the GaN layer. The above two GaN monolayers can also achieve the effect of converting the bias stress inside the film into a tensile stress, thereby achieving the effect of weakening the QCSE and increasing the In integration rate.

[0018] As a preferred technical solution of the present invention, the hole density in the GaN single layer with a porous structure is within the range of 10 per square centimeter. 10 ~10 15 , such as 10 in the square centimeter range 10 , 10 11 , 10 12 , 10 13 , 10 14 or 10 15 The above numerical ranges are not limited to the above numerical ranges, and other numerical values ​​not listed are also applicable.

[0019] A second object of the present invention is to provide a method for preparing any of the above-mentioned lasers, the method comprising growing a stress release layer on the surface of the lower waveguide layer, growing a quantum well active region on the surface of the stress release layer, and the quantum well active region forming a three-dimensional morphology.

[0020] In the present invention, the preparation method of the laser comprises growing an InGaN / GaN superlattice structure layer on the surface of the InGaN lower waveguide layer as a stress release layer, and forming a three-dimensional morphology on the surface of the InGaN / GaN superlattice structure layer;

[0021] A quantum well active region is grown on the surface of the InGaN / GaN superlattice structure layer, and the In element content of the InGaN / GaN superlattice structure layer is greater than the In element content of the quantum well active region.

[0022] In the present invention, the method for preparing the laser comprises growing an InGaN single layer on the surface of the InGaN lower waveguide layer as a stress release layer, wherein the surface of the InGaN single layer forms a three-dimensional morphology;

[0023] A quantum well active region is grown on the surface of the InGaN single layer, and the In element content of the InGaN single layer is greater than the In element content of the quantum well active region.

[0024] In the present invention, the preparation method of the laser includes growing a GaN single layer on the surface of the GaN lower waveguide layer as a stress release layer, the surface of the GaN single layer forms a three-dimensional morphology; and growing a quantum well active region on the surface of the GaN single layer.

[0025] As a preferred technical solution of the present invention, when the stress release layer is an InGaN / GaN superlattice structure layer, the temperature of growing the stress release layer is 700-800°C, the pressure is 200-500 torr, and the ratio of ammonia to MO source is 1000-10000.

[0026] Among them, the temperature of the growing stress release layer can be 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C or 800°C, etc., the pressure can be 200torr, 250torr, 300torr, 350torr, 400torr, 450torr or 500torr, etc., and the ratio of ammonia to MO source can be 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 or 10000, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical ranges are also applicable.

[0027] In the present invention, the setting of the process conditions of the InGaN / GaN superlattice structure layer can improve the performance of the stress release layer and prepare for the growth of subsequent quantum wells. Among them, the relatively low temperature can improve the infiltration of In, and the high pressure can improve the crystallization rate of In in the film. Since N vacancies are easily formed at low temperatures, it is necessary to suppress them with a high ratio of ammonia and MO sources to improve the quality of the film, thereby forming a stress-reversed high In infiltration and high-quality stress release structure.

[0028] Preferably, when the stress release layer is an InGaN single layer, the temperature for growing the stress release layer is 800-900° C., the growth pressure is 100-300 torr, and the ratio of ammonia gas to MO source is 1000-5000.

[0029] Among them, the temperature of the growing stress release layer can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C, etc., the pressure can be 100torr, 120torr, 150torr, 180torr, 200torr, 220torr, 250torr, 280torr or 300torr, etc., and the ratio of ammonia to MO source can be 1000, 2000, 3000, 4000 or 5000, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical ranges are also applicable.

[0030] As a preferred technical solution of the present invention, when the stress release layer is a GaN single layer, the growth temperature of the GaN single layer with a porous structure is 500-600°C, such as 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In the present invention, a GaN single layer with a porous structure is prepared by using a relatively low growth temperature.

[0032] Preferably, the ratio of ammonia and MO sources in the GaN single layer with supersaturated Ga element content is 1 to 100, such as 1, 2, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90 or 100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In the present invention, supersaturation of Ga atoms is achieved through a low 5:3 ratio, and Ga atoms occupy the N position to prepare a GaN monolayer supersaturated with Ga atoms.

[0034] As a preferred technical solution of the present invention, the actual growth temperature of the quantum well active region grown on the surface of the stress release layer is greater than the predetermined growth temperature.

[0035] Among them, the predetermined growth temperature refers to the growth temperature of the traditional quantum well active region, which is generally 600-800°C, while the growth temperature of the traditional blue-green light quantum well active region is 700-800°C. The actual growth temperature of the quantum well active region grown on the surface of the stress release layer of the present invention is greater than the predetermined growth temperature, which can make the growth temperature of the quantum well active region break through the upper limit of the growth temperature of the traditional blue-green light quantum well active region. The reason is that the introduction of the stress release layer in the above-mentioned GaN-based laser converts the compressive stress in the film into tensile stress, causing the material interface to fluctuate, thereby increasing the In integration rate, so that the growth temperature of the quantum well active region is increased.

[0036] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0037] (1) The present invention provides a laser and a method for preparing the same. The GaN-based laser adds a stress release structure before the quantum well active region is grown, thereby reducing the mismatch stress during the growth of the quantum well active region, reducing the crystal defects and polarization electric field in the active region, thereby weakening the QCSE and increasing the overlap of electron-hole wave functions, which is beneficial to improving the radiation recombination efficiency of the GaN-based laser and increasing its limitation factor, thereby achieving the effect of improving performance such as power;

[0038] (2) The present invention provides a laser and a method for preparing the same, wherein the laser improves the actual In integration rate of the active region, thereby increasing the growth temperature of the quantum well active region, thereby improving the growth quality of the quantum well active region and the overall laser performance;

[0039] (2) The present invention provides a laser and a method for preparing the same. The preparation method is simple to operate, has good process repeatability, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of the structure of a GaN-based laser provided in Examples 1-3 of the present invention;

[0041] Figure 2 A schematic diagram of the structure of a conventional GaN-based laser provided in Comparative Examples 1-3 of the present invention;

[0042] Figure 3 This is the epitaxial structure and schematic diagram of the traditional GaN-based laser;

[0043] Figure 4 The GaN-based laser epitaxial structure and its principle diagram provided by the present invention;

[0044] Figure 5 Comparison of quantum well growth morphology of active region of GaN-based laser provided by conventional structure (a) and the present invention (b);

[0045] In the figure: 1-substrate layer, 2-lower confinement layer, 3-lower waveguide layer, 4-stress release layer, 5-quantum well active region, 6-upper waveguide layer, 7-electron blocking layer, 8-upper confinement layer, 9-ohmic contact layer.

[0046] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0048] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0049] Example 1

[0050] This embodiment provides a laser, wherein the GaN-based laser comprises a quantum well active region 5 and a lower waveguide layer 3, wherein a stress release layer 4 is disposed between the quantum well active region 5 and the lower waveguide layer 3; the GaN-based laser further comprises an upper waveguide layer 6, an electron blocking layer 7, an upper confinement layer 8 and an ohmic contact layer 9 connected in sequence by the surface of the quantum well active region 5, and a lower confinement layer 2 and a substrate layer 1 connected in sequence by the lower surface of the lower waveguide layer;

[0051] The quantum well active region 5 is an InGaN / GaN quantum well active region, the lower waveguide layer 3 is an InGaN lower waveguide layer, the stress release layer 4 is an InGaN / GaN superlattice structure layer, the upper waveguide layer 6 is an InGaN upper waveguide layer, the electron blocking layer 7 is a p-AlGaN electron blocking layer, the upper confinement layer 8 is a p-AlGaN upper confinement layer, the ohmic contact layer 9 is a p-GaN ohmic contact layer, the lower confinement layer 2 is an n-AlGaN lower confinement layer, and the substrate layer 1 is an n-type GaN substrate;

[0052] The preparation method of the GaN-based laser is as follows: using a GaN single crystal substrate, growing an 850nm thick Si-doped AlGaN lower confinement layer on the substrate, wherein the Al component is controlled to be 8%; then growing a 60nm thick non-doped InGaN lower waveguide layer, wherein the In component is controlled to be 3%; growing an InGaN / GaN superlattice stress release layer, wherein the InGaN thickness is 2.5nm, the In component is controlled to be 20%, and the GaN thickness is 2.5nm, and the cycle is repeated for 5 cycles, the growth temperature is 750°C, and the growth pressure is 2.5°C. The pressure is 300torr, and the ratio of ammonia to MO source is 3000; then grow an InGaN / GaN quantum well active region, with the In component controlled at 15%, the InGaN thickness is 3nm, the GaN thickness is 7nm, and the cycle is repeated for 2 cycles at a growth temperature of 760°C; grow a 60nm thick non-doped InGaN upper waveguide layer, with the In component controlled at 3%; grow an 850nm thick Mg-doped AlGaN upper confinement layer, with the Al component controlled at 5%; finally grow a 10nm thick Mg-highly doped GaN ohmic contact layer.

[0053] Example 2

[0054] In this embodiment, except that the growth temperature of the InGaN / GaN superlattice stress release layer is 700° C., the growth pressure is 500 torr, and the ratio of ammonia gas to MO source is 1000, the other conditions are the same as those in Embodiment 1.

[0055] Example 3

[0056] In this embodiment, except that the growth temperature of the InGaN / GaN superlattice stress release layer is 800° C., the growth pressure is 200 torr, and the ratio of ammonia gas to MO source is 10000, the other conditions are the same as those in Embodiment 1.

[0057] Example 4

[0058] This embodiment provides a laser, in which the stress release layer 4 is an InGaN single layer, the growth temperature of the InGaN single layer is 850° C., the growth pressure is 200 torr, the ratio of ammonia to MO source is 3000, and the other conditions are the same as those in Embodiment 1.

[0059] Example 5

[0060] This embodiment provides a laser, in which the stress release layer 4 is an InGaN single layer, the growth temperature of the InGaN single layer is 800° C., the growth pressure is 300 torr, the ratio of ammonia to MO source is 1000, and the other conditions are the same as those in Embodiment 1.

[0061] Example 6

[0062] This embodiment provides a laser, in which the stress release layer 4 is an InGaN single layer, the growth temperature of the InGaN single layer is 800° C., the growth pressure is 300 torr, the ratio of ammonia to MO source is 1000, and the other conditions are the same as those in Embodiment 1.

[0063] Example 7

[0064] This embodiment provides a laser, in which the stress release layer 4 is a GaN single layer with a porous structure, the growth temperature of the GaN single layer is 550°C, the growth pressure is 200 torr, the ratio of ammonia to MO source is 3000, and the other conditions are the same as those in Example 1.

[0065] Example 8

[0066] This embodiment provides a laser, in which the stress release layer 4 is a GaN single layer with a porous structure, the growth temperature of the GaN single layer is 500°C, the growth pressure is 200 torr, the ratio of ammonia and MO source is 3000, and the other conditions are the same as those in Example 1.

[0067] Example 9

[0068] This embodiment provides a laser, in which the stress release layer 4 is a GaN single layer with a porous structure, the growth temperature of the GaN single layer is 600°C, the growth pressure is 200 torr, the ratio of ammonia and MO source is 3000, and the other conditions are the same as those in Example 1.

[0069] Example 10

[0070] This embodiment provides a laser, in which the stress release layer 4 is a GaN single layer supersaturated with Ga, the growth temperature of the GaN single layer is 750°C, the growth pressure is 200 torr, the ratio of ammonia to MO source is 50, and the other conditions are the same as those in Example 1.

[0071] Embodiment 11

[0072] This embodiment provides a laser, in which the stress release layer 4 is a GaN single layer supersaturated with Ga, the growth temperature of the GaN single layer is 750°C, the growth pressure is 200 torr, the ratio of ammonia and MO source is 1, and the other conditions are the same as those in Example 1.

[0073] Example 12

[0074] This embodiment provides a laser, in which the stress release layer 4 is a GaN single layer supersaturated with Ga, the growth temperature of the GaN single layer is 750°C, the growth pressure is 200 torr, the ratio of ammonia and MO source is 100, and the other conditions are the same as those in Example 1.

[0075] Embodiment 13

[0076] This embodiment provides a laser. Except that the growth temperature of the InGaN / GaN quantum well active region is 850° C., other conditions are the same as those of the first embodiment.

[0077] Embodiment 14

[0078] This embodiment provides a laser. Except that the In content in the InGaN / GaN superlattice stress release layer is controlled at 15% and the In content in the InGaN / GaN quantum well active region is controlled at 10%, other conditions are the same as those in Embodiment 1.

[0079] Embodiment 15

[0080] This embodiment provides a laser. Except that the In content in the InGaN / GaN superlattice stress release layer is controlled at 25% and the In content in the InGaN / GaN quantum well active region is controlled at 20%, other conditions are the same as those in Embodiment 1.

[0081] Comparative Example 1

[0082] This comparative example provides a laser, wherein the GaN-based laser has the same conditions as those of Example 1 except that the stress release layer 4 is not provided;

[0083] The preparation method of the GaN-based laser is as follows: using a GaN single crystal substrate, growing an 850nm thick Si-doped AlGaN lower confinement layer on the substrate, with the Al component controlled at 8%; then growing a 60nm thick non-doped InGaN lower waveguide layer, with the In component controlled at 3%; then growing an InGaN / GaN quantum well active region, with the In component controlled at 15%, the InGaN thickness being 3nm, the GaN thickness being 7nm, and the cycle being repeated for 2 cycles, with the growth temperature being 750°C; growing a 60nm thick non-doped InGaN upper waveguide layer, with the In component controlled at 3%; growing an 850nm thick Mg-doped AlGaN upper confinement layer, with the Al component controlled at 5%; and finally growing a 10nm thick Mg-highly doped GaN ohmic contact layer.

[0084] Comparative Example 2

[0085] This comparative example provides a laser. Except that the growth temperature of the InGaN / GaN quantum well active region is 850° C., other conditions are the same as those of comparative example 1.

[0086] Comparative Example 3

[0087] This comparative example provides a laser, in which the stress release layer 4 is a GaN single layer, the growth temperature of the GaN single layer is 750°C, the growth pressure is 200 torr, the ratio of ammonia to MO source is 3000, and the other conditions are the same as those in Example 1.

[0088] Comparative Example 4

[0089] This comparative example provides a laser, in which the conditions are the same as those of Example 15 except that the growth of the InGaN / GaN superlattice stress release layer is not performed.

[0090] Examples 1-15 and Comparative Examples 1-4 were subjected to the same chip process, and the laser performance was tested, and the In component content of the actual active area was tested. The results show that the quantum well half-height, threshold current, and threshold voltage of Examples 1-15 are all smaller than those of Comparative Example 1, and the lasing wavelength and optical power of Examples 1-15 are higher than those of Comparative Example 1, indicating that the overall performance of the laser is improved by adding a stress release layer, especially the radiation recombination efficiency and the final laser lasing gain are improved; compared with Comparative Example 2, Example 1 has an increased growth temperature in the quantum well active area, and does not cause In precipitation in the active area due to the increase in temperature. Therefore, by adding a stress release layer, not only the growth temperature of the active area is increased, thereby improving the epitaxial quality, but also no other problems are caused by the increase in temperature. This effect is particularly important for the green light band with a high In component; when compared with Comparative Example 1, Examples 1-6 and Examples 14-15 have improved their laser performance. The In component of the actual active region can also meet the requirements, which proves that the stress release layer with high In component can not only accelerate the release of mismatch stress, but also reduce the crystal defects and polarization electric field in the active region, so that the bias stress state inside the film is converted into a tensile stress state. During the subsequent growth of InGaN / GaN quantum wells, the material interface is undulating, and more In components can be absorbed. Compared with Comparative Example 3, the quantum well half height, threshold current, and threshold voltage of Examples 7-13 are all smaller than those of Comparative Example 3, and the lasing wavelength and optical power are all higher than those of Comparative Example 3, indicating that stress relaxation is performed for the subsequent growth of the quantum well active region through the porous GaN monolayer, or the stress state is changed through the Ga-saturated GaN monolayer, which also achieves the effect of weakening QCSE and increasing the In integration rate. Compared with Example 15, when the InGaN / GaN quantum well is grown without setting a stress release layer, Comparative Example 4 cannot make the In component content in the InGaN / GaN quantum well reach 20%, and In will precipitate during the growth process, while there is no In precipitation in Example 15, which proves that the addition of the stress release layer allows the subsequent growth of the InGaN / GaN quantum well to absorb more In components.

[0091] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0092] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0093] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0094] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A laser, characterized in that: The laser at least comprises a quantum well active region and a lower waveguide layer, a stress release layer is arranged between the quantum well active region and the lower waveguide layer, and the quantum well active region has a three-dimensional morphology; The stress release layer is an InGaN / GaN superlattice structure layer, an InGaN single layer or a GaN single layer; When the stress release layer is an InGaN / GaN superlattice structure layer or an InGaN single layer, the In element content of the stress release layer is greater than the In element content of the quantum well active region; The lower waveguide layer is an InGaN waveguide layer; The In element content of the quantum well active region is greater than the In element content of the InGaN waveguide layer; The In element content of the stress release layer is 15% to 25%, and the In element content of the quantum well active region is 10% to 20%; The stress release layer converts the bias stress inside the film before the stress release layer grows into a tensile stress. When the quantum well active region is subsequently grown, the material interface fluctuates, and the tensile stress makes the quantum well active region have a three-dimensional morphology.

2. The laser according to claim 1, characterized in that The thickness of the InGaN single layer or GaN single layer is 5-50 nm, and the thickness of the InGaN layer and the GaN layer in the InGaN / GaN superlattice structure layer are independently 1-5 nm.

3. The laser according to claim 1, characterized in that When the stress release layer is a GaN single layer, the GaN single layer at least includes a porous structure or supersaturated Ga atoms.

4. The laser according to claim 3, characterized in that The hole density in the GaN monolayer with a porous structure is in the range of 10 per square centimeter. 10 ~10 15 .

5. A method for preparing a laser, characterized in that: The preparation method is used to prepare the laser according to any one of claims 1 to 4, and the preparation method includes growing a stress release layer on the surface of the lower waveguide layer, growing a quantum well active region on the surface of the stress release layer, and the quantum well active region forms a three-dimensional morphology.

6. The preparation method according to claim 5, characterized in that: When the stress release layer is an InGaN / GaN superlattice structure layer, the temperature of growing the stress release layer is 700-800° C., the pressure is 200-500 torr, and the ratio of ammonia gas to MO source is 1000-10000.

7. The preparation method according to claim 5, characterized in that: When the stress release layer is an InGaN single layer, the temperature for growing the stress release layer is 800-900° C., the growth pressure is 100-300 torr, and the ratio of ammonia gas to MO source is 1000-5000.

8. The preparation method according to claim 5, characterized in that: When the stress release layer is a GaN single layer, the growth temperature of the GaN single layer with a porous structure is 500-600°C.

9. The preparation method according to claim 8, characterized in that: The ratio of the ammonia gas to the MO source in the GaN single layer with supersaturated Ga element content is 1-100.

10. The preparation method according to claim 5, characterized in that: The actual growth temperature of the quantum well active region grown on the surface of the stress release layer is greater than the predetermined growth temperature.

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