MLED epitaxial wafer and preparation method thereof

Abstract

The invention relates to the technical field of epitaxial wafer preparation, in particular to an MLED epitaxial wafer and a preparation method thereof.The preparation method comprises the steps that a low-temperature buffer layer, an undoped GaN layer, an N-type GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer are sequentially grown on a substrate, the electron blocking layer is grown on the multi-quantum well layer, and the P-type semiconductor layer is grown on the substrate; when the electron barrier layer is prepared, the ScaAlbGa1-a-bN layer, the AlGaN layer and the BcAldGa1-c-dN layer are sequentially stacked from bottom to top, so that the problem of uneven current density distribution caused by poor current expansion of an epitaxial layer is solved.

Description

Technical Field

[0001] The invention relates to the technical field of epitaxial wafer preparation, and in particular to an MLED epitaxial wafer and a preparation method thereof. Background Art

[0002] LED chip is a semiconductor electronic component that can emit light and is widely used in lighting and other fields. LED epitaxial wafer is a solid light source, which is a light-emitting device made of semiconductor PN junction. When the forward current is turned on, the electrons and holes in the semiconductor recombine, and the released energy is emitted in the form of photons or part of it in the form of photons. LED epitaxial wafer lighting has significant advantages such as high efficiency, energy saving, environmental protection and long service life. It has been widely used in various aspects such as street lights, display screens, indoor lighting and car lights. Light efficiency is the most important measure of the competitiveness of LED epitaxial wafers. How to improve the light efficiency of LED epitaxial wafers based on existing technologies is an eternal topic to increase the competitiveness of LED epitaxial wafers.

[0003] MLED is a general term for Mini-LED and Micro-LED. Its various performances are superior to existing display technologies such as LCD and OLED, and it is the next generation display technology with the most competitive advantage. According to the chip size, MLED display is usually divided into two major areas: Mini-LED with chip size between 100μm and 200μm; Micro-LED with chip size below 100μm. MLED has a small area and high requirements for current expansion. In the case of external current, it is very easy to cause the chip voltage to increase or even burn due to the current congestion effect. The light-emitting diode epitaxial wafer and its preparation method and light-emitting diode disclosed in the publication number CN116995167A propose to set an insertion layer between the N-type GaN layer and the multi-quantum well layer. The insertion layer includes a MgN nucleation layer, an AlN three-dimensional layer and a ScAlGaN filling layer. Although the current crowding effect is alleviated, the defects and dislocations in the GaN material still exist, and the stability is poor. Therefore, a better and more stable current expansion is needed to solve the voltage problem of MLED to improve the light efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, provide an MLED epitaxial wafer and a preparation method thereof, so as to solve the problem of uneven current density distribution caused by poor current expansion in the epitaxial layer and ensure the stability of the light emitting diode.

[0005] The technical solution adopted by the present application to solve the technical problem is as follows: the method for preparing an MLED epitaxial wafer includes sequentially growing a low-temperature buffer layer, an undoped GaN layer, an N-type GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer on a substrate, wherein the electron blocking layer is grown on the multi-quantum well layer, and the electron blocking layer is sequentially stacked from bottom to top.a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d N layers.

[0006] The substrate can be a sapphire flat substrate or a patterned substrate.

[0007] The Sc a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d N layer, forming a high impedance characteristic material, better confining electrons in the quantum well region, reducing electron leakage, and increasing the recombination probability of electron-hole pairs to improve device performance; at the same time, due to Sc a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d The bandgap width of the N layer decreases gradually as it moves away from the quantum well layer, which is beneficial for the holes in the P layer to move more evenly toward the quantum well, forming better current expansion to improve light efficiency.

[0008] The electron blocking layer is doped with element Mg, and the doping concentration of Mg is: 1E18atoms / cm 3 ~5E19atoms / cm 3 , growth temperature is 900℃~1000℃, and growth pressure is 100torr~260torr.

[0009] The a=0.01-0.35, b=0.05-0.25, c=0.01-0.3, d=0.05-0.35.

[0010] The Sc a Al b Ga 1-a-b The thickness of the N layer ranges from 10nm to 30nm, the thickness of the AlGaN layer ranges from 8nm to 25nm, and the thickness of the B c Al d Ga 1-c-d The thickness of the N layer is 5nm to 20nm.

[0011] The low temperature buffer layer growth process is as follows:

[0012] First, an AlN thin film layer is deposited by a PVD method. During the growth of the AlN thin film layer, the growth temperature is controlled to be 550° C. to 680° C., the sputtering power is 3200W to 4400W, and the pressure is 1 torr to 10 torr, and finally an AlN buffer layer of 10nm to 30nm is deposited.

[0013] Subsequently, in the MOCVD equipment, hydrogen is introduced at a high temperature of 1050°C-1150°C and a low pressure of 50Torr-200Torr to clean the substrate surface, and then the temperature is lowered to 500°C-650°C and the pressure is 150Torr-600Torr to grow a low-temperature buffer layer;

[0014] 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.

[0015] The undoped GaN layer is grown in an MOCVD device. During the growth of the undoped GaN layer, the growth temperature is controlled to be 950° C. to 1150° C. and the pressure is controlled to be 50 torr to 500 torr. Finally, a 1 μm to 3 μm undoped GaN layer is deposited.

[0016] Growing the N-type GaN layer in a MOCVD device, wherein the N-type GaN layer is a 4-layer N-type doped GaN layer, and the dopant is Si;

[0017] When growing the N-type GaN layer, the temperature in the MOCVD equipment reaction chamber is controlled to be 1080℃~1180℃, and the pressure is 100torr~450torr. Finally, a 1.5μm~3μm N-type doped GaN layer is deposited. The doping element of the N-type GaN layer is Si, and the doping concentration of Si is 1E17atoms / cm 3 ~1E20atoms / cm 3 .

[0018] When the stress release layer is grown, the temperature of the reaction chamber is adjusted to 750-950° C., the pressure of the reaction chamber is controlled to be 100 torr-500 torr, and the growth thickness is 50 nm-100 nm.

[0019] When the multi-quantum well layer is grown and prepared, the temperature of the reaction chamber is controlled at 750° C. to 950° C., the pressure of the reaction chamber is controlled at 100 torr to 500 torr, and 10 to 15 periods of quantum well layers are grown;

[0020] The quantum well layer includes alternately grown GaN quantum barriers and InGaN quantum wells, with a total thickness of about 150nm-250nm;

[0021] The P-type semiconductor layer is a composite layer of a P-type GaN layer and a P-type contact layer deposited in sequence;

[0022] The P-type GaN layer and the P-type contact layer are doped with element Mg, wherein the doping concentration of Mg in the P-type GaN layer is 3E19atoms / cm 3 ~3E20atoms / cm 3 , thickness 30nm~120nm, growth temperature 900℃~1000℃, growth pressure 150torr~600torr;

[0023] The doping concentration of Mg in the P-type contact layer is 8E19atoms / cm 3 ~8E20atoms / cm 3 , thickness 10nm~30nm, growth temperature 900℃~1000℃, growth pressure 200torr~600torr;

[0024] 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 1 min to 10 min. The epitaxial growth is completed after the temperature drops to room temperature.

[0025] An MLED epitaxial wafer comprises a substrate, a low temperature buffer layer, an undoped GaN layer, an N-type GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer arranged in sequence from bottom to top. The MLED epitaxial wafer is prepared by the above-mentioned MLED epitaxial wafer preparation method. The electron blocking layer comprises Sc a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d N layers.

[0026] Compared with the prior art, this application has the following beneficial effects:

[0027] The present application utilizes ScAlGaN, AlGaN and BAlGaN high impedance characteristic materials to better confine electrons in the quantum well region, reduce electron leakage, and increase the recombination probability of electron-hole pairs to improve device performance; at the same time, because the bandgap width of the ScAlGaN layer, the AlGaN layer and the BAlGaN layer gradually decreases as it moves away from the quantum well layer, it is beneficial for the holes in the P layer to move more evenly toward the quantum well, forming a better current expansion to improve the light efficiency.

[0028] AlGaN can improve the crystallization quality of GaN materials because 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 in BAlGaN can easily fill the defects and dislocations in the GaN material, forming a stable unit cell structure and reducing the presence of defects, thereby improving the luminous efficiency of the light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the production process of the present invention;

[0030] Figure 2 It is a schematic diagram of the epitaxial structure of the present invention.

[0031] In the figure: 100, substrate; 200, low temperature buffer layer; 300, undoped GaN layer; 400, N-type GaN layer; 500, stress release layer; 600, multi-quantum well layer; 700, electron blocking layer; 710, Sc a Al b Ga 1-a-b N layer; 720, AlGaN layer; 730, B c Al d Ga 1-c-d N layer; 800, P-type semiconductor layer. DETAILED DESCRIPTION

[0032] 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.

[0033] Example 1

[0034] A substrate 100 is prepared; then a low-temperature buffer layer 200 is grown on the substrate 100. Specifically, an AlN thin film layer is first deposited by a PVD method. During the growth of the AlN thin film layer, the growth temperature is controlled to be 600°C, the sputtering power is 4000W, and the pressure is 8torr, and finally a 20nm AlN buffer layer is deposited;

[0035] Subsequently, in the MOCVD device, hydrogen is introduced at a high temperature of 1050° C. and a low pressure of 100 Torr to clean the surface of the substrate 100 , and then the temperature is lowered to 600° C. and the pressure is 600 Torr to grow a low-temperature buffer layer;

[0036] The in-situ annealing treatment was carried out in a hydrogen atmosphere at a temperature of 1100°C and a pressure of 200 torr.

[0037] Growing an undoped GaN layer 300 on the low-temperature buffer layer 200: growing the undoped GaN layer 300 in an MOCVD device, controlling the growth temperature to 950° C. and the pressure to 200 torr, and finally depositing a 1.5 μm undoped GaN layer 300 .

[0038] Growing an N-type GaN layer 400 on the undoped GaN layer 300: growing the N-type GaN layer 400 in an MOCVD device, with Si as the dopant;

[0039] When growing the N-type GaN layer 400, the temperature in the MOCVD equipment reaction chamber is controlled to be 1120°C and the pressure is 200 torr. Finally, a 2μm N-type doped GaN layer is deposited. The doping element of the N-type GaN layer is Si, and the doping concentration of Si is 3E19 atoms / cm 3 .

[0040] The stress release layer 500 is grown on the N-type GaN layer 400 : when the stress release layer 500 is grown, the temperature of the reaction chamber is adjusted to 850° C., the pressure of the reaction chamber is controlled to 200 torr, and the growth thickness is 75 nm.

[0041] The multi-quantum well layer 600 is grown on the stress release layer 500: the quantum well layer comprises GaN quantum barriers and InGaN quantum wells grown alternately, with a total thickness of 170 nm, the temperature of the reaction chamber is controlled at about 880° C. when growing the quantum barriers, the temperature of the reaction chamber is controlled at about 750° C. when growing the quantum wells, the pressure of the reaction chamber is controlled at 200 torr, and 11 periods of quantum well layers are grown;

[0042] An electron blocking layer 700 is grown on the multi-quantum well layer 600. The electron blocking layer 700 is prepared by sequentially stacking Sc a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d N layers.

[0043] The electron blocking layer 700 has Sc a Al b Ga 1-a-b The thickness of the N layer 710 is 12 nm, a=0.2, b=0.15, the thickness of the AlGaN layer 720 is 10 nm, B c Al d Ga 1-c-d The thickness of the N layer 730 is 8 nm, c=0.15, d=0.1.

[0044] The electron blocking layer 700 is doped with element Mg, and the doping concentration of Mg is: 5E18atoms / cm 3 , growth temperature 950℃, growth pressure 200tor.

[0045] A P-type semiconductor layer 800 is grown on the electron blocking layer 700 , wherein the P-type semiconductor layer 800 includes a composite layer of a P-type GaN layer and a P-type contact layer deposited in sequence;

[0046] The P-type GaN layer and the P-type contact layer are doped with element Mg, wherein the doping concentration of Mg in the P-type GaN layer is 3E19atoms / cm 3 , thickness 120nm, growth temperature 900℃, growth pressure 200torr;

[0047] The doping concentration of Mg in the P-type contact layer is 8E19atoms / cm 3 , thickness 30nm, growth temperature 900℃, growth pressure 600torr;

[0048] 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. for 4 minutes. The epitaxial growth is completed after the temperature drops to room temperature.

[0049] Example 2

[0050] A sapphire Al2O3 flat substrate 100 is prepared; then a low-temperature buffer layer 200 is grown on the substrate 100. Specifically, an AlN thin film layer is first deposited by a PVD method. During the growth of the AlN thin film layer, the growth temperature is controlled to be 680°C, the sputtering power is 3200W, and the pressure is 1torr, and finally a 10nm AlN buffer layer is deposited;

[0051] Subsequently, in the MOCVD device, hydrogen is introduced at a high temperature of 1150° C. and a low pressure of 50 Torr to clean the surface of the substrate 100, and then the temperature is lowered to 650° C. and the pressure is 300 Torr to grow a low-temperature buffer layer;

[0052] The in-situ annealing treatment was carried out in a hydrogen atmosphere at a temperature of 1000°C and a pressure of 500 torr.

[0053] Growing an undoped GaN layer 300 on the low-temperature buffer layer 200: growing the undoped GaN layer 300 in an MOCVD device, controlling the growth temperature to 1150° C. and the pressure to 50 torr, and finally depositing a 1 μm undoped GaN layer 300 .

[0054] Growing an N-type GaN layer 400 on the undoped GaN layer 300: growing the N-type GaN layer 400 in an MOCVD device, wherein the N-type GaN layer 400 is a 4-layer N-type doped GaN layer, and the dopant is Si;

[0055] When growing the N-type GaN layer 400, the temperature in the MOCVD equipment reaction chamber is controlled to be 1080°C and the pressure is 450torr. Finally, a 3μm N-type doped GaN layer is deposited. The doping element of the N-type GaN layer is Si, and the doping concentration of Si is 1E20atoms / cm 3 .

[0056] The stress release layer 500 is grown on the N-type GaN layer 400 : when the stress release layer 500 is grown, the temperature of the reaction chamber is adjusted to 950° C., the pressure of the reaction chamber is controlled to 100 torr, and the growth thickness is 100 nm.

[0057] The multi-quantum well layer 600 is grown on the stress release layer 500: the temperature of the reaction chamber is controlled at 850° C., the pressure of the reaction chamber is controlled at 300 torr, and 13 periods of quantum well layers are grown;

[0058] The quantum well layer contains alternately grown GaN quantum barriers and InGaN quantum wells, with a total thickness of 150nm;

[0059] An electron blocking layer 700 is grown on the multi-quantum well layer 600. The electron blocking layer 700 is prepared by sequentially stacking Sc a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d N layers.

[0060] The electron blocking layer 700 has Sc a Al b Ga 1-a-b The thickness of the N layer 710 is 12 nm, a=0.3, b=0.1, the thickness of the AlGaN layer 720 is 10 nm, B c Al d Ga 1-c-d The thickness of the N layer 730 is 8 nm, c=0.2, d=0.1.

[0061] The electron blocking layer 700 is doped with element Mg, and the doping concentration of Mg is: 2E18atoms / cm 3 , growth temperature 900℃, growth pressure 260torr;

[0062] A P-type semiconductor layer 800 is grown on the electron blocking layer 700 , wherein the P-type semiconductor layer 800 includes a composite layer of a P-type GaN layer and a P-type contact layer deposited in sequence;

[0063] The P-type GaN layer and the P-type contact layer are both doped with element Mg, wherein the doping concentration of Mg in the P-type GaN layer is 3E20atoms / cm 3 , thickness 30nm, growth temperature 1000℃, growth pressure 150torr;

[0064] The Mg doping concentration in the P-type contact layer is 8E20atoms / cm 3 , thickness 10nm, growth temperature 1000℃, growth pressure 200torr;

[0065] 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 850°C for 1 minute. The epitaxial growth is completed after the temperature drops to room temperature.

[0066] Example 3

[0067] A sapphire pattern substrate 100 is prepared; then a low-temperature buffer layer 200 is grown on the substrate 100. Specifically, an AlN thin film layer is first deposited by a PVD method. During the growth of the AlN thin film layer, the growth temperature is controlled to be 600°C, the sputtering power is 3800W, and the pressure is 10torr, and finally a 30nm AlN buffer layer is deposited;

[0068] Subsequently, in the MOCVD device, hydrogen is introduced at a high temperature of 1100° C. and a low pressure of 150 Torr to clean the surface of the substrate 100 , and then the temperature is lowered to 550° C. and the pressure is 150 Torr to grow a low-temperature buffer layer;

[0069] The in-situ annealing treatment was carried out in a hydrogen atmosphere at a temperature of 1100°C and a pressure of 3500 torr.

[0070] Growing an undoped GaN layer 300 on the low-temperature buffer layer 200: growing the undoped GaN layer 300 in an MOCVD device, controlling the growth temperature to 1000° C. and the pressure to 400 torr, and finally depositing a 3 μm undoped GaN layer 300 .

[0071] Growing an N-type GaN layer 400 on the undoped GaN layer 300: growing the N-type GaN layer 400 in an MOCVD device, wherein the N-type GaN layer 400 is a 4-layer N-type doped GaN layer, and the dopant is Si;

[0072] When growing the N-type GaN layer 400, the temperature in the MOCVD equipment reaction chamber is controlled to be 1180°C and the pressure is 100 torr. Finally, a 2μm N-type doped GaN layer is deposited. The doping element of the N-type GaN layer is Si, and the doping concentration of Si is 1E17atoms / cm 3 .

[0073] The stress release layer 500 is grown on the N-type GaN layer 400 : when the stress release layer 500 is grown, the temperature of the reaction chamber is adjusted to 750° C., the pressure of the reaction chamber is controlled at 500 torr, and the growth thickness is 50 nm.

[0074] The multi-quantum well layer 600 is grown on the stress release layer 500: the temperature of the reaction chamber is controlled at 950° C., the pressure of the reaction chamber is controlled at 100 torr, and 10 periods of quantum well layers are grown;

[0075] The quantum well layer contains alternately grown GaN quantum barriers and InGaN quantum wells, with a total thickness of 160nm;

[0076] An electron blocking layer 700 is grown on the multi-quantum well layer 600. The electron blocking layer 700 is prepared by sequentially stacking Sc a Al b Ga 1-a-b N layer, AlGaN layer and B c Al d Ga 1-c-d N layers.

[0077] The electron blocking layer 700 has Sc a Al b Ga 1-a-b The thickness of the N layer 710 is 12 nm, a=0.2, b=0.15, the thickness of the AlGaN layer 720 is 10 nm, B c Al d Ga 1-c-d The thickness of the N layer 730 is 8 nm, c=0.15, d=0.1.

[0078] The electron blocking layer 700 is doped with element Mg, and the doping concentration of Mg is: 4E19atoms / cm 3 , growth temperature 950℃, growth pressure 200torr;

[0079] A P-type semiconductor layer 800 is grown on the electron blocking layer 700, and the P-type semiconductor layer 800 is a composite layer of a P-type GaN layer and a P-type contact layer deposited in sequence;

[0080] The P-type GaN layer and the P-type contact layer are doped with element Mg, wherein the doping concentration of Mg in the P-type GaN layer is 3E19atoms / cm3 , thickness 90nm, growth temperature 950℃, growth pressure 400torr;

[0081] The Mg doping concentration in the P-type contact layer is 8E20atoms / cm 3 , thickness 20nm, growth temperature 960℃, growth pressure 350torr;

[0082] 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 750° C. for 6 minutes. The epitaxial growth is completed after the temperature drops to room temperature.

[0083] Example 4

[0084] The difference from Example 1 is that the electron blocking layer contains Sc a Al b Ga 1-a-b The thickness of the N layer is 20nm, a=0.2, b=0.15, the thickness of the AlGaN layer is 15nm, B c Al d Ga 1-c-d The thickness of the N layer is 12 nm, c=0.15, d=0.1.

[0085] Example 5

[0086] The difference from Example 1 is that the electron blocking layer contains Sc a Al b Ga 1-a-b The thickness of the N layer is 8nm, a=0.2, b=0.15, the thickness of the AlGaN layer is 13nm, B c Al d Ga 1-c-d The thickness of the N layer is 18 nm, c=0.15, d=0.1.

[0087] Example 6

[0088] The difference from Example 1 is that the electron blocking layer contains Sc a Al b Ga 1-a-b N layers a=0.02,b=0.25,B c Al d Ga 1-c-d N layer c=0.02, d=0.33.

[0089] Example 7

[0090] The difference from Example 1 is that the electron blocking layer contains Sc a Al b Ga 1-a-bN layer a=0.33,b=0.05,B c Al d Ga 1-c-d N layers c=0.3, d=0.05.

[0091] Comparative Example 1

[0092] The difference from Example 1 is that: there is no Sc in the electron blocking layer a Al b Ga 1-a-b The thickness of the N layer and the AlGaN layer is 20 nm, and the rest is the same as in the first embodiment.

[0093] Comparative Example 2

[0094] The difference from Example 1 is that: there is no Sc in the electron blocking layer a Al b Ga 1-a-b N layer and B c Al d Ga 1-c-d The thickness of the N layer and the AlGaN layer is 30 nm, and the rest is the same as in Example 1.

[0095] The comparison table of the light efficiency improvement effects of Examples 1-7 and Comparative Examples 1 and 2 is as follows:

[0096]

[0097] Referring to the above table, the light efficiencies of Examples 1-7 and Comparative Example 1 of the present application are improved relative to Comparative Example 2, wherein the improvement of Examples 1-7 exceeds 0.50%, and the improvement effect is better.

[0098] 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 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 method for preparing an MLED epitaxial wafer, comprising sequentially growing a low-temperature 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), an electron blocking layer (700) and a P-type semiconductor layer (800) on a substrate (100), characterized in that: The electron blocking layer (700) is grown on the multi-quantum well layer (600), and the electron blocking layer (700) is prepared by sequentially stacking Sc a Al b Ga 1-a-b N layer (710), AlGaN layer (720) and B c Al d Ga 1-c-d N layers (730).

2. The method for preparing an MLED epitaxial wafer according to claim 1, characterized in that: The electron blocking layer (700) is doped with element Mg, and the doping concentration of Mg is: 1E18atoms / cm 3 ~5E19atoms / cm 3 , growth temperature is 900℃~1000℃, and growth pressure is 100torr~260torr.

3. The method for preparing an MLED epitaxial wafer according to claim 1 or 2, characterized in that: The a=0.01-0.35, b=0.05-0.25, c=0.01-0.3, d=0.05-0.

35.

4. The method for preparing an MLED epitaxial wafer according to claim 1 or 2, characterized in that: The Sc a Al b Ga 1-a-b The thickness of the N layer (710) is in the range of 10 nm to 30 nm, the thickness of the AlGaN layer (720) is in the range of 8 nm to 25 nm, and the B c Al d Ga 1-c-d The thickness of the N layer (730) is 5 nm to 20 nm.

5. The method for preparing an MLED epitaxial wafer according to claim 1, characterized in that: The growth process of the low temperature buffer layer (200) is as follows: The AlN thin film layer is deposited by a PVD method. During the growth of the AlN thin film layer, the growth temperature is controlled to be 550° C. to 680° C., the sputtering power is 3200W to 4400W, and the pressure is 1 torr to 10 torr, and finally a 10nm to 30nm AlN buffer layer is deposited; In an MOCVD device, hydrogen is introduced at a high temperature of 1050° C.-1150° C. and a low pressure of 50 Torr-200 Torr to clean the surface of the substrate (100), and then the temperature is lowered to 500° C.-650° C. and the pressure is 150 Torr-600 Torr 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.

6. The method for preparing an MLED epitaxial wafer according to claim 1, characterized in that: In the process of growing the undoped GaN layer (300), the growth temperature is controlled to be 950° C. to 1150° 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.

7. The method for preparing an MLED epitaxial wafer according to claim 1, characterized in that: The N-type GaN layer (400) is a 4-layer N-type doped GaN layer, and the dopant is Si; When growing the N-type GaN layer (400), the temperature is 1080°C to 1180°C, the pressure is 100 torr to 450 torr, and finally a 1.5 μm to 3 μm N-type doped GaN layer is deposited, and the doping concentration of Si is 1E17 atoms / cm 3 ~1E20atoms / cm 3 .

8. The method for preparing an MLED epitaxial wafer according to claim 1, characterized in that: When the stress release layer (500) is grown, the temperature is adjusted to 750-950° C., the pressure of the reaction chamber is controlled to be 100 torr-500 torr, and the growth thickness is 50 nm-100 nm.

9. The method for preparing an MLED epitaxial wafer according to claim 1, characterized in that: When the multi-quantum well layer (600) is grown and prepared, the temperature is controlled at 750° C. to 950° C., the pressure is controlled at 100 torr to 500 torr, and 10 to 15 periods of quantum well layers are grown; The quantum well layer includes alternately grown GaN quantum barriers and InGaN quantum wells, with a total thickness of 150nm-250nm; The P-type semiconductor layer (800) comprises a composite layer of a P-type GaN layer and a P-type contact layer deposited in sequence; The P-type GaN layer and the P-type contact layer are both doped with element Mg, wherein the doping concentration of Mg in the P-type GaN layer is 3E19atoms / cm 3 ~3E20atoms / cm 3 , thickness 30nm~120nm, growth temperature 900℃~1000℃, growth pressure 150torr~600torr; The doping concentration of Mg in the P-type contact layer is 8E19atoms / cm 3 ~8E20atoms / cm 3 , thickness 10nm~30nm, growth temperature 900℃~1000℃, growth pressure 200torr~600torr.

10. An MLED epitaxial wafer, comprising a substrate (100), a low-temperature 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), an electron blocking layer (700) and a P-type semiconductor layer (800) arranged in sequence from bottom to top, characterized in that: The MLED epitaxial wafer is prepared by the MLED epitaxial wafer preparation method according to any one of claims 1 to 9, wherein the electron blocking layer (700) comprises Sc a Al b Ga 1-a-b N layer (710), AlGaN layer (720) and B c Al d Ga 1-c-d N layers (730).

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