GAN-based light-emitting diode epitaxial wafer and preparation method thereof

Abstract

The present invention relates to the field of semiconductor technology, and in particular to a GAN-based light-emitting diode epitaxial wafer and a preparation method thereof. The epitaxial wafer comprises an AlN buffer layer, an undoped GaN layer, an N-type GaN layer, a stress release layer, a multi-quantum well layer, a P-type AlGaN electron blocking layer and a P-type GaN layer which are sequentially grown on a substrate; the N-type GaN layer comprises four sublayers, each sublayer is doped with Si at a different concentration, and BGaN and AlGaN layers are inserted in the middle to improve the crystallization quality of the epitaxial layer, thereby solving the technical problems of poor crystallization quality of the epitaxial layer and uneven current density distribution.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a GAN-based light-emitting diode epitaxial wafer and a preparation method thereof. Background Art

[0002] At present, the epitaxial layer structure of GaN-based light-emitting diodes includes a substrate, on which a buffer layer, an undoped GaN layer, a doped GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer are deposited in sequence. During the growth process, the nucleation layer generates linear defects and continuously grows upward, which has a great impact on the crystal quality of the GaN epitaxial layer.

[0003] There are mainly the following problems in growing GaN-based epitaxial layers on sapphire substrates. First, there is a very large lattice mismatch between the Al2O3 material of the sapphire substrate and the GaN material of the epitaxial layer, which easily generates line defects during the growth process. Line defects not only act as non-radiative recombination centers, but also introduce energy levels in the bandgap, reducing the photon lifetime and the luminous efficiency of the light-emitting diode. Second, most GaN-based LEDs are non-vertical structures. Conventional lighting is mainly upright, while MiniLED is mainly inverted. Both have the problem of uneven current density distribution.

[0004] The GaN-based light-emitting diode epitaxial wafer and its manufacturing method disclosed in publication number CN106910801A improve the optoelectronic performance of the epitaxial wafer, but the substrate material used for MOCVD heteroepitaxial GaN and the GaN epitaxial layer still have a large lattice mismatch and thermal expansion coefficient mismatch, and heteroepitaxial growth under large mismatch conditions often leads to a high defect density in the epitaxial layer. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a GAN-based light-emitting diode epitaxial wafer and a preparation method thereof.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a GAN-based light-emitting diode epitaxial wafer, comprising an AlN buffer layer, an undoped GaN layer, an N-type GaN layer, a stress release layer, a multi-quantum well layer, a P-type AlGaN electron blocking layer and a P-type GaN layer grown sequentially on a substrate;

[0007] The N-type GaN layer includes four sub-layers, and each sub-layer is doped with Si at a different concentration.

[0008] The first layer of the N-type GaN layer is a low Si-doped GaN layer;

[0009] The second layer is GaN with little Si doping, BGaN superlattice without Si doping and AlGaN superlattice without Si doping;

[0010] The third layer is highly Si-doped GaN and Si-free GaN;

[0011] The fourth layer is a GaN layer slightly doped with Si.

[0012] The concentration of the first layer of Si is set to C1;

[0013] The concentration of the second Si layer is set to C2, the thickness of GaN is h1, the thickness of BGaN is h2, the thickness of AlGaN is h3, and the number of superlattice periods is n1;

[0014] The concentration of the third layer of Si is set to C3, and the number of superlattice periods is n2;

[0015] The concentration of Si in the fourth layer is set to C4;

[0016] C3>C1>C2>C4, h3>h2>h1.

[0017] The thickness range of h1 is 1-5 nm, the thickness range of h2 is 2-7 nm, the thickness range of h3 is 3-10 nm, and the number range of n1 is 3-20.

[0018] The value range of C1 is 1E18atoms / cm 3 ~1E19atoms / cm 3 ;

[0019] The value range of C2 is 1E17atoms / cm 3 ~1E18atoms / cm 3 ;

[0020] The value range of C3 is 1E19atoms / cm 3 ~1E20atoms / cm 3 ;

[0021] The value range of C4 is 1E17atoms / cm 3 ~1E18atoms / cm 3 .

[0022] The method for preparing the above-mentioned GAN-based light-emitting diode epitaxial wafer comprises the following steps:

[0023] S1: growing an AlN buffer layer on a substrate;

[0024] S2: growing an undoped GaN layer on the AlN buffer layer;

[0025] S3: growing an N-type GaN layer on the undoped GaN layer;

[0026] S4: growing a stress release layer on the N-type GaN layer;

[0027] S5: growing a multi-quantum well layer on the stress release layer;

[0028] S6: growing a P-type AlGaN electron blocking layer on the multi-quantum well layer;

[0029] S7: growing a P-type semiconductor layer on the P-type AlGaN electron blocking layer.

[0030] In S1, the AlN buffer layer is deposited by PVD method, and the specific process is as follows:

[0031] In the process of growing the AlN buffer layer, the growth temperature is controlled to be 500° C. to 650° C., the sputtering power is controlled to be 3000W to 4400W, and the pressure is controlled to be 1 torr to 10 torr, and finally a 10nm to 40nm AlN buffer layer is deposited;

[0032] In the MOCVD equipment, hydrogen is introduced at high temperature (1050℃-1150℃) and low pressure (50Torr-200Torr) to clean the surface of the sapphire substrate (Al2O3), and then the temperature is lowered to 500℃-550℃ and the pressure is 150Torr-600Torr to grow a low-temperature buffer layer;

[0033] The in-situ annealing treatment is performed in a hydrogen atmosphere at a temperature of 1000° C. to 1200° C. and a pressure of 150 torr to 500 torr.

[0034] In S2, an undoped GaN layer is grown in a MOCVD device. During the growth process, the growth temperature is controlled to be 1050° C. to 1200° C. and the pressure is controlled to be 50 torr to 500 torr. Finally, an undoped GaN layer of 1 μm to 3 μm is deposited.

[0035] The N-type GaN layer in S3 is grown in a MOCVD device, the temperature in the MOCVD reaction chamber is 1100° C. to 1200° C., and the pressure is 100 torr to 300 torr, and finally a 1 μm to 3 μm N-type doped GaN layer is deposited.

[0036] The N-type GaN layer in S3 is 4 layers of N-type doped GaN layers, and the dopant is Si, comprising the following sub-steps:

[0037] S3-1: Grow the first low-Si-doped GaN layer with a doping concentration of 1E18atoms / cm 3 ~1E19atoms / cm 3 ;

[0038] S3-2: Grow the second layer of GaN-BGaN-AlGaN superlattice, where the GaN part is not doped with Si, and the BGaN and AlGaN parts are lightly doped with Si, with a doping concentration of 1E17atoms / cm 3 ~1E18atoms / cm 3 , the thickness of GaN in a single period is 1 to 5 nm, the thickness of BGaN is 2 to 7 nm, the thickness of AlGaN is 3 to 10 nm, the number of periods in the superlattice is 3 to 20, and the thickness is 30 to 100 nm;

[0039] S3-3: Growth of the third layer of highly Si-doped GaN and undoped GaN superlattice with a doping concentration of 1E19 atoms / cm 3 ~1E20atoms / cm 3 ;

[0040] S3-4: Growth of the fourth slightly Si-doped GaN layer with a doping concentration of 1E17 atoms / cm 3 ~1E18atoms / cm 3 .

[0041] Compared with the prior art, the present invention has the following beneficial effects: the present invention improves the crystal quality of the epitaxial layer and solves the technical problems of poor crystal quality of the epitaxial layer and uneven current density distribution;

[0042] The growth method of the superlattice makes the carriers confined in space, resulting in quantization of energy states. This quantum confinement effect changes the electronic band structure of the superlattice material, thus having better optical and electrical properties.

[0043] In the present application, BGaN and AlGaN can improve the crystallization quality of GaN materials. The reason is that the atomic radius between Ga atoms and Al atoms is very different, which can suppress dislocations and thus make the crystallization quality of the GaN layer better. The smaller B atoms can easily fill the defects and dislocations in the GaN material, forming a stable unit cell structure and reducing the presence of defects, thereby reducing the probability of non-radiative recombination of carriers at defects, thereby improving the crystallization quality of the material, reducing the non-radiative recombination efficiency of quantum wells, and improving the luminescence efficiency of light-emitting diodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the epitaxial wafer structure of the present invention.

[0045] In the figure: 100, substrate; 200, AlN buffer layer; 300, undoped GaN layer; 400, N-type GaN layer; 410, low Si-doped GaN layer; 420, lightly Si-doped GaN; 421, BGaN; 422, AlGaN; 430, highly Si-doped GaN; 431, undoped Si GaN; 440, slightly Si-doped GaN layer; 500, stress release layer; 600, multi-quantum well layer; 700, P-type AlGaN electron blocking layer; 800, P-type semiconductor layer. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example 1

[0048] Reference Figure 1 , a GAN-based light-emitting diode epitaxial wafer, comprising an AlN buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a stress release layer 500, a multi-quantum well layer 600, a P-type AlGaN electron blocking layer 700 and a P-type GaN layer 800 sequentially grown on a substrate 100;

[0049] The N-type GaN layer 400 includes four sub-layers, and each sub-layer is doped with Si at a different concentration.

[0050] The first layer of the N-type GaN layer 400 is a low Si-doped GaN layer 410;

[0051] The second layer is a superlattice of GaN420 with little Si doping, BGaN421 without Si doping and AlGaN422 without Si doping;

[0052] The third layer is highly Si-doped GaN430 and Si-free GaN431;

[0053] The fourth layer is a GaN layer 440 slightly doped with Si.

[0054] The concentration of the first layer of Si is set to C1;

[0055] The concentration of the second Si layer is set to C2, the thickness of GaN is h1, the thickness of BGaN is h2, the thickness of AlGaN is h3, and the number of superlattice periods is n1;

[0056] The concentration of the third layer of Si is set to C3, and the number of superlattice periods is n2;

[0057] The concentration of Si in the fourth layer is set to C4;

[0058] C3>C1>C2>C4, h3>h2>h1.

[0059] The thickness range of h1 is 1-5 nm, the thickness range of h2 is 2-7 nm, the thickness range of h3 is 3-10 nm, and the number range of n1 is 3-20.

[0060] The value range of C1 is 1E18atoms / cm 3 ~1E19atoms / cm 3 ;

[0061] The value range of C2 is 1E17atoms / cm 3 ~1E18atoms / cm 3 ;

[0062] The value range of C3 is 1E19atoms / cm 3 ~1E20atoms / cm 3 ;

[0063] The value range of C4 is 1E17atoms / cm 3 ~1E18atoms / cm 3 .

[0064] Example 2

[0065] The method for preparing the above-mentioned GAN-based light-emitting diode epitaxial wafer comprises the following steps:

[0066] S1: growing an AlN buffer layer 200 on the substrate 100;

[0067] In the present application, the substrate 100 is a sapphire Al2O3 plane or pattern substrate;

[0068] In S1, the AlN buffer layer 200 is deposited by a PVD method, and the specific process is as follows:

[0069] During the growth of the AlN buffer layer 200 , the growth temperature is controlled to be 500° C. to 650° C., the sputtering power is controlled to be 3000W to 4400W, and the pressure is controlled to be 1 torr to 10 torr, and finally a 10 nm to 40 nm AlN buffer layer is deposited;

[0070] In the MOCVD equipment, hydrogen is introduced at a high temperature of 1050℃-1150℃ and a low pressure of 50Torr-200Torr to clean the Al2O3 surface of the sapphire substrate, and then the temperature is lowered to 500℃-550℃ and the pressure is 150Torr-600Torr to grow a low-temperature buffer layer;

[0071] The in-situ annealing treatment is performed in a hydrogen atmosphere at a temperature of 1000° C. to 1200° C. and a pressure of 150 torr to 500 torr.

[0072] S2: growing an undoped GaN layer 300 on the AlN buffer layer 200; in S2, the undoped GaN layer 300 is grown in an MOCVD device, and during the growth process, the growth temperature is controlled to be 1050° C. to 1200° C. and the pressure is controlled to be 50 torr to 500 torr, and finally a 1 μm to 3 μm undoped GaN layer 300 is deposited.

[0073] S3: growing an N-type GaN layer 400 on the undoped GaN layer 300; in S3, the N-type GaN layer 400 is grown in an MOCVD device, the temperature in the MOCVD reaction chamber is 1100° C. to 1200° C., the pressure is 100 torr to 300 torr, and finally a 1 μm to 3 μm N-type doped GaN layer is deposited.

[0074] The N-type GaN layer 400 in S3 is 4 layers of N-type doped GaN layers, and the dopant is Si, which specifically includes the following sub-steps:

[0075] S3-1: growing the first low-Si-doped GaN layer 410 with a doping concentration of 1E18 atoms / cm 3 ~1E19atoms / cm 3 ;

[0076] S3-2: Grow the second layer of GaN-BGaN-AlGaN superlattice, where the GaN part is not doped with Si, and the BGaN and AlGaN parts are lightly doped with Si, with a doping concentration of 1E17atoms / cm 3 ~1E18atoms / cm 3 , the thickness of GaN in a single period is 1 to 5 nm, the thickness of BGaN is 2 to 7 nm, the thickness of AlGaN is 3 to 10 nm, the number of periods in the superlattice is 3 to 20, and the thickness is 30 to 100 nm;

[0077] S3-3: Growth of the third layer of highly Si-doped GaN430 and Si-free GaN431 superlattice with a doping concentration of 1E19 atoms / cm 3 ~1E20atoms / cm 3 ;

[0078] S3-4: growing the fourth slightly Si-doped GaN layer 440, with a doping concentration of 1E17 atoms / cm 3 ~1E18atoms / cm 3 .

[0079] S4: growing a low-temperature stress release layer 500 on the N-type GaN layer 400; adjusting the temperature of the reaction chamber to 750-900° C., controlling the pressure of the reaction chamber to 100-500 torr, and growing a stress release layer with a thickness of 50-100 nm.

[0080] S5: growing a multi-quantum well layer 600 on the stress release layer 500; the temperature of the reaction chamber is controlled at 750-900°C, the pressure of the reaction chamber is controlled at 100-500torr, and 10-15 periods of quantum well layers are grown, the quantum well layers contain quantum barriers and quantum wells grown alternately, and the total thickness is about 150-250nm of In x Ga 1-x N / GaN quantum well layer; x only represents the doping coefficient, and the specific value can be determined according to actual conditions.

[0081] S6: growing a P-type AlGaN electron blocking layer 700 on the multi-quantum well layer 600; the P-type AlGaN electron blocking layer 700 is an AlGaN layer doped with Mg, and the Mg doping concentration is 3E18atoms / cm 3 ~1E19atoms / cm 3 , thickness 30nm~100nm, growth temperature 900℃~1000℃, growth pressure 100torr~260torr.

[0082] S7: growing a P-type semiconductor layer on the P-type AlGaN electron blocking layer 700. The P-type semiconductor layer is a composite layer of a P-type GaN layer and a P-type contact layer deposited in sequence. The P-type GaN layer is a GaN layer doped with Mg, and the Mg doping concentration is 3E19atoms / cm 3 ~1E20atoms / cm 3 , thickness 30nm~120nm, growth temperature 900℃~1000℃, growth pressure 150torr~600torr. The P-type contact layer is a Mg-doped GaN layer, and the Mg doping concentration is 8E19atoms / cm 3 ~5E20atoms / cm 3 , thickness 10nm~30nm, growth temperature 900℃~1000℃, growth pressure 200torr~600torr. The P-type GaN layer mainly provides holes for the PN junction, which are used for radiative recombination and luminescence with N-type electrons; the P-type contact layer forms a good ohmic contact for the electrode during the later chip production.

[0083] After the epitaxial structure growth is completed, the temperature of the reaction chamber is lowered and annealing is performed in a nitrogen atmosphere at a temperature of 650° C. to 850° C. for 2 min to 12 min. The epitaxial growth is completed when the temperature drops to room temperature.

[0084] Example 3

[0085] On the basis of Embodiment 1 and Embodiment 2, the present invention includes, from bottom to top, a sapphire substrate 100, a low-temperature AlN buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a low-temperature stress release layer 500, a multi-quantum well layer 600, a P-type AlGaN electron blocking layer 700, and a P-type semiconductor layer 800;

[0086] The second layer of the GaN-BGaN-AlGaN superlattice grown in the N-type GaN layer has a GaN thickness of 1.5 nm, a BGaN thickness of 2.5 nm, and an AlGaN thickness of 3.5 nm in each period, and the number of periods of this superlattice is 10.

[0087] Example 4

[0088] On the basis of Embodiment 1 and Embodiment 2, the present invention includes, from bottom to top, a sapphire substrate 100, a low-temperature AlN buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a low-temperature stress release layer 500, a multi-quantum well layer 600, a P-type AlGaN electron blocking layer 700, and a P-type semiconductor layer 800;

[0089] The second layer of the GaN-BGaN-AlGaN superlattice grown in the N-type GaN layer has a GaN thickness of 2nm, a BGaN thickness of 3nm, and an AlGaN thickness of 4nm in each period, and the number of periods of this superlattice is 8.

[0090] Example 5

[0091] On the basis of Embodiment 1 and Embodiment 2, the present invention includes, from bottom to top, a sapphire substrate 100, a low-temperature AlN buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a low-temperature stress release layer 500, a multi-quantum well layer 600, a P-type AlGaN electron blocking layer 700, and a P-type semiconductor layer 800;

[0092] The second layer of the GaN-BGaN-AlGaN superlattice grown in the N-type GaN layer has a GaN thickness of 1 nm, a BGaN thickness of 1.5 nm, and an AlGaN thickness of 2.5 nm in each period, and the number of periods of the superlattice is 12.

[0093] Example 6

[0094] On the basis of Embodiment 1 and Embodiment 2, the present invention includes, from bottom to top, a sapphire substrate 100, a low-temperature AlN buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a low-temperature stress release layer 500, a multi-quantum well layer 600, a P-type AlGaN electron blocking layer 700, and a P-type semiconductor layer 800;

[0095] The second layer of the GaN-BGaN-AlGaN superlattice grown in the N-type GaN layer has a GaN thickness of 2.5 nm, a BGaN thickness of 3 nm, and an AlGaN thickness of 3.5 nm in each period, and the number of periods of this superlattice is 8.

[0096] Example 7

[0097] On the basis of Embodiment 1 and Embodiment 2, the present invention includes, from bottom to top, a sapphire substrate 100, a low-temperature AlN buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a low-temperature stress release layer 500, a multi-quantum well layer 600, a P-type AlGaN electron blocking layer 700, and a P-type semiconductor layer 800;

[0098] The second layer of the GaN-BGaN-AlGaN superlattice grown in the N-type GaN layer has a GaN thickness of 3 nm, a BGaN thickness of 4 nm, and an AlGaN thickness of 5 nm in each period, and the number of periods of this superlattice is 5.

[0099] Comparative Example 1:

[0100] This comparative example provides a method for growing an LED epitaxial structure, which is different from Example 3 in that there is no GaN-BGaN-AlGaN superlattice layer grown as the second layer in the N-type GaN layer, and the rest is the same as Example 3.

[0101] Comparative Example 2

[0102] This comparative example provides a method for growing an LED epitaxial structure, which is different from Example 3 in that there is no BGaN layer in the second grown GaN-BGaN-AlGaN superlattice layer in the N-type GaN layer, and the rest is the same as Example 3.

[0103] The relevant experimental data of Examples 3-7 and Comparative Examples 1-2 are compared as shown in the following table:

[0104]

[0105] The meanings of "002" and "102" in the above table are: the half-width in the 002 / 102 direction is detected by high-resolution X-ray diffractometer (HRXRD) to characterize it. 002 and 102 represent two different crystal plane directions of the crystal. The two half-width values ​​are related to the dislocation density. The larger the value, the more dislocations and the worse the crystal quality. Usually, the half-width value in the 002 direction represents screw dislocations, and the half-width value in the 102 direction represents edge dislocations.

[0106] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A GAN-based light-emitting diode epitaxial wafer, characterized in that: It comprises an AlN buffer layer (200), an undoped GaN layer (300), an N-type GaN layer (400), a stress release layer (500), a multi-quantum well layer (600), a P-type AlGaN electron blocking layer (700) and a P-type semiconductor layer (800) which are sequentially grown on a substrate (100); The N-type GaN layer (400) includes four sub-layers, each sub-layer being doped with Si at a different concentration.

2. The GAN-based light-emitting diode epitaxial wafer according to claim 1, characterized in that: The first layer of the N-type GaN layer (400) is a low-Si-doped GaN layer (410); The second layer is a superlattice of GaN (420) with little Si doping, BGaN (421) without Si doping and AlGaN (422) without Si doping; The third layer is highly Si-doped GaN (430) and Si-free GaN (431); The fourth layer is a GaN layer (440) slightly doped with Si.

3. The GAN-based light-emitting diode epitaxial wafer according to claim 2, characterized in that: The concentration of the first layer of Si is set to C1; The concentration of the second Si layer is set to C2, the thickness of GaN is h1, the thickness of BGaN is h2, the thickness of AlGaN is h3, and the number of superlattice periods is n1; The concentration of the third layer of Si is set to C3, and the number of superlattice periods is n2; The concentration of Si in the fourth layer is set to C4; C3>C1>C2>C4, h3>h2>h1.

4. The GAN-based light-emitting diode epitaxial wafer according to claim 3, characterized in that: The thickness range of h1 is 1-5 nm, the thickness range of h2 is 2-7 nm, the thickness range of h3 is 3-10 nm, and the number range of n1 is 3-20.

5. The GAN-based light-emitting diode epitaxial wafer according to claim 3, characterized in that: The value range of C1 is 1E18atoms / cm 3 ~1E19atoms / cm 3 ; The value range of C2 is 1E17atoms / cm 3 ~1E18atoms / cm 3 ; The value range of C3 is 1E19atoms / cm 3 ~1E20atoms / cm 3 ; The value range of C4 is 1E17atoms / cm 3 ~1E18atoms / cm 3 .

6. The method for preparing the GAN-based light-emitting diode epitaxial wafer according to any one of claims 1 to 5, characterized in that: The steps include: S1: growing an AlN buffer layer (200) on a substrate (100); S2: growing an undoped GaN layer (300) on the AlN buffer layer (200); S3: growing an N-type GaN layer (400) on the undoped GaN layer (300); S4: growing a stress release layer (500) on the N-type GaN layer (400); S5: growing a multi-quantum well layer (600) on the stress release layer (500); S6: growing a P-type AlGaN electron blocking layer (700) on the multi-quantum well layer (600); S7: growing a P-type semiconductor layer (800) on the P-type AlGaN electron blocking layer (700).

7. The method for preparing a GAN-based light-emitting diode epitaxial wafer according to claim 6, characterized in that: In S1, the AlN buffer layer (200) is deposited by a PVD method, and the specific process is as follows: In the process of growing the AlN buffer layer (200), the growth temperature is controlled to be 500° C. to 650° C., the sputtering power is controlled to be 3000W to 4400W, and the pressure is controlled to be 1 torr to 10 torr, and finally a 10nm to 40nm AlN buffer layer is deposited; In the MOCVD equipment, hydrogen is introduced at 1050°C-1150°C and 50Torr-200Torr to clean the substrate surface, and then the temperature is lowered to 500°C-550°C and the pressure is 150Torr-600Torr to grow a low-temperature buffer layer; The in-situ annealing treatment is performed in a hydrogen atmosphere at a temperature of 1000° C. to 1200° C. and a pressure of 150 torr to 500 torr.

8. The method for preparing a GAN-based light-emitting diode epitaxial wafer according to claim 6, characterized in that: In S2, an undoped GaN layer (300) is grown in an MOCVD device. During the growth process, the growth temperature is controlled to be 1050° C. to 1200° C. and the pressure is controlled to be 50 torr to 500 torr. Finally, an undoped GaN layer (300) of 1 μm to 3 μm is deposited.

9. The method for preparing a GAN-based light-emitting diode epitaxial wafer according to claim 6, characterized in that: The N-type GaN layer (400) in S3 is grown in a MOCVD device, the temperature in the MOCVD reaction chamber is 1100° C. to 1200° C., the pressure is 100 torr to 300 torr, and finally a 1 μm to 3 μm N-type doped GaN layer is deposited.

10. The method for preparing a GAN-based light-emitting diode epitaxial wafer according to claim 9, characterized in that: The S3 includes the following sub-steps: S3-1: grow the first low Si-doped GaN layer (410) with a doping concentration of 1E18 atoms / cm 3 ~1E19atoms / cm 3 ; S3-2: Grow the second layer of GaN-BGaN-AlGaN superlattice, where the GaN part is not doped with Si, and the BGaN and AlGaN parts are lightly doped with Si, with a doping concentration of 1E17atoms / cm 3 ~1E18atoms / cm 3 , the thickness of GaN in a single period is 1 to 5 nm, the thickness of BGaN is 2 to 7 nm, the thickness of AlGaN is 3 to 10 nm, the number of periods in the superlattice is 3 to 20, and the thickness is 30 to 100 nm; S3-3: Growth of the third layer of highly Si-doped GaN (430) and undoped GaN (431) superlattice with a doping concentration of 1E19 atoms / cm 3 ~1E20atoms / cm 3 ; S3-4: growing the fourth slightly Si-doped GaN layer (440) with a doping concentration of 1E17 atoms / cm 3 ~1E18atoms / cm 3 .

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