Method for preparing light-emitting diode epitaxial wafer for improving crystal quality

Abstract

The present disclosure provides a method for preparing a light-emitting diode epitaxial wafer with improved crystal quality, belonging to the technical field of light-emitting diodes. After growing a basic AlN layer on a substrate, a graphene layer is deposited on the surface of the basic AlN layer, and then the basic AlN layer is annealed to improve the crystal quality of the obtained basic AlN layer. A graphene layer is also deposited on the basic AlN layer. The relatively dense graphene layer with a large chemical property difference from the basic AlN layer covers the surface of the basic AlN layer, which can inhibit the nitrogen atom desorption process that may occur on the surface of the basic AlN layer during annealing, improve the internal crystal quality and surface flatness of the basic AlN layer after annealing, and also reduce impurity adsorption. A basic AlN layer with better quality is obtained, and an n-type layer, a light-emitting layer, and a p-type layer are sequentially grown on the basic AlN layer with better quality, effectively improving the quality of the finally obtained light-emitting diode epitaxial wafer.

Description

Technical Field

[0001] The present disclosure relates to the technical field of light-emitting diodes, and particularly to a method for preparing a light-emitting diode epitaxial wafer with improved crystal quality. Background Art

[0002] A light-emitting diode is a very widely used light-emitting device, commonly used in traffic signal lights, internal and external automotive lights, urban lighting, medical detection or purification, etc. A light-emitting diode epitaxial wafer is the basic structure for preparing a light-emitting diode. A light-emitting diode epitaxial wafer generally includes a substrate and an AlN layer, an n-type layer, a light-emitting layer, and a p-type layer sequentially stacked on the substrate.

[0003] The AlN layer can play a transitional role and alleviate the lattice mismatch problem between the substrate and materials such as the n-type layer to be grown. And in order to improve the growth quality of the AlN layer itself, an annealing treatment is performed on the AlN layer after the AlN layer is grown. However, during the annealing process of the AlN layer, nitrogen atoms on the surface of the AlN layer are prone to desorption problems, resulting in a relatively rough surface of the AlN layer, affecting the quality of the n-type layer grown on the surface of the AlN layer, and ultimately the crystal quality of the obtained light-emitting diode epitaxial wafer is still not ideal enough. Summary of the Invention

[0004] Embodiments of the present disclosure provide a method for preparing a light-emitting diode epitaxial wafer with improved crystal quality, which can improve the crystal quality of the obtained light-emitting diode epitaxial wafer. The technical solution is as follows:

[0005] Embodiments of the present disclosure provide a method for preparing a light-emitting diode epitaxial wafer with improved crystal quality, and the method for preparing a light-emitting diode epitaxial wafer with improved crystal quality includes:

[0006] Providing a substrate;

[0007] Depositing a basic AlN layer on the substrate;

[0008] Depositing a graphene layer on the basic AlN layer;

[0009] Performing an annealing treatment on the basic AlN layer;

[0010] Peeling off the graphene layer on the surface of the basic AlN layer;

[0011] Growing an n-type layer, a light-emitting layer, and a p-type layer on the basic AlN layer in sequence.

[0012] Optionally, the thickness of the graphene layer is 50 - 500 nm.

[0013] Optionally, laser peeling is used to peel off the graphene layer on the surface of the basic AlN layer.

[0014] Optionally, a basic AlN layer is deposited on the substrate by using a physical vapor deposition device, and the deposition temperature of the basic AlN layer is 550 - 650 °C.

[0015] Optionally, the thickness of the basic AlN layer is 10 - 500 nm.

[0016] Optionally, the basic AlN layer is annealed at a temperature of 1600 - 1800 °C.

[0017] Optionally, the basic AlN layer is annealed for 2.5 - 3.5 h at a temperature of 1600 - 1800 °C.

[0018] Optionally, the method for preparing a light - emitting diode epitaxial wafer for improving crystal quality further includes: after peeling off the graphene layer on the surface of the basic AlN layer, before sequentially growing an n - type layer, a light - emitting layer, and a p - type layer on the basic AlN layer,

[0019] an AlN transition layer is grown on the basic AlN layer.

[0020] Optionally, the thickness of the AlN transition layer is 1.5 - 2.5 microns.

[0021] Optionally, the growth temperature of the AlN transition layer is 1300 - 1400 °C.

[0022] The beneficial effects brought by the technical solutions provided in the embodiments of the present disclosure include:

[0023] After growing a basic AlN layer on the substrate and depositing a graphene layer on the surface of the basic AlN layer, the basic AlN layer is annealed. Annealing can reduce the stress in the basic AlN layer, reduce the defects caused by the stress in the basic AlN layer to improve the crystal quality of the obtained basic AlN layer. It reduces the possible cracking on the surface of the basic AlN layer to improve the crystal quality of the epitaxial material grown on the basic AlN layer. Since a graphene layer is also deposited on the basic AlN layer, the relatively dense graphene layer with a large chemical property difference from the basic AlN layer covers the surface of the basic AlN layer, which can inhibit the nitrogen atom desorption process that may occur on the surface of the basic AlN layer during annealing, improving the internal crystal quality and surface flatness of the basic AlN layer after annealing. The graphene layer can also prevent the formation of impurities such as oxygen, carbon, and aluminum - containing oxides on the surface of the basic AlN layer, and a basic AlN layer with a smooth surface and fewer impurities can be obtained. After annealing, peeling off the graphene layer on the surface of the basic AlN layer can obtain a basic AlN layer with good quality, and an n - type layer, a light - emitting layer, and a p - type layer are sequentially grown on the basic AlN layer with good quality, effectively improving the quality of the finally obtained light - emitting diode epitaxial wafer. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0025] Figure 1 is a flowchart of a method for preparing a light-emitting diode epitaxial wafer to improve crystal quality provided by an embodiment of the present disclosure;

[0026] Figure 2 is a schematic structural diagram of a light-emitting diode epitaxial wafer provided by an embodiment of the present disclosure;

[0027] Figure 3 is a flowchart of another method for preparing a light-emitting diode epitaxial wafer to improve crystal quality provided by an embodiment of the present disclosure;

[0028] Figure 4 is a schematic structural diagram of another light-emitting diode epitaxial wafer provided by an embodiment of the present disclosure. Specific Embodiments

[0029] To make the purpose, technical solutions, and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in detail with reference to the accompanying drawings.

[0030] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meaning understood by those of ordinary skill in the art to which the present disclosure pertains. The "first", "second", "third", and similar terms used in the specification and claims of the present patent application do not denote any order, quantity, or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "one" do not denote a quantity limitation, but indicate the presence of at least one. The terms "include" or "comprise" and the like mean that the elements or items appearing before "include" or "comprise" cover the elements or items listed after "include" or "comprise" and their equivalents, and do not exclude other elements or items. The terms "connect" or "be connected" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", "top", "bottom", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationships may also change accordingly.

[0031] Figure 1 is a flowchart of a method for preparing a light-emitting diode epitaxial wafer to improve crystal quality provided by an embodiment of the present disclosure, as Figure 1As shown in the figure, an embodiment of the present disclosure provides a method for fabricating a light-emitting diode epitaxial wafer with improved crystal quality. The method for fabricating a light-emitting diode epitaxial wafer with improved crystal quality includes:

[0032] S101: Provide a substrate.

[0033] S102: Deposit a base AlN layer on the substrate.

[0034] S103: Deposit a graphene layer on the base AlN layer.

[0035] S104: Anneal the base AlN layer.

[0036] S105: Strip the graphene layer on the surface of the base AlN layer.

[0037] S106: Sequentially grow an n-type layer, a light-emitting layer, and a p-type layer on the base AlN layer.

[0038] After growing the base AlN layer on the substrate and depositing the graphene layer on the surface of the base AlN layer, the base AlN layer is annealed. Annealing can reduce the stress in the base AlN layer, reduce the defects caused by the stress in the base AlN layer, and improve the crystal quality of the obtained base AlN layer. It can reduce the possible cracking on the surface of the base AlN layer to improve the crystal quality of the epitaxial material grown on the base AlN layer. Since there is also a graphene layer deposited on the base AlN layer, the relatively dense graphene layer with a large chemical property difference from the base AlN layer covers the surface of the base AlN layer, which can inhibit the nitrogen atom desorption process that may occur on the surface of the base AlN layer during the annealing process, and improve the internal crystal quality and surface flatness of the base AlN layer after annealing. The graphene layer can also prevent the formation of impurities such as oxygen, carbon, and aluminum-containing oxides on the surface of the base AlN layer, and a base AlN layer with a smooth surface and fewer impurities can be obtained. After annealing, stripping the graphene layer on the surface of the base AlN layer can obtain a base AlN layer with better quality, and an n-type layer, a light-emitting layer, and a p-type layer are sequentially grown on the base AlN layer with better quality, effectively improving the quality of the finally obtained light-emitting diode epitaxial wafer.

[0039] Exemplarily, in step S103, the graphene layer can be grown by a chemical vapor deposition device. A relatively dense and high-quality graphene layer can be obtained.

[0040] Optionally, in step S103, the growth temperature and growth pressure of the graphene layer can be 1000 - 1200 °C and 0.1 - 1 atm.

[0041] When the growth temperature and growth pressure of the graphene layer are respectively within the above ranges, a relatively dense graphene layer can be obtained.

[0042] Exemplarily, in step S103, the growth rate of the graphene layer can be 10 to 200 nm / s. The density of the graphene layer can be further increased to more effectively suppress the possible desorption on the surface of the underlying AlN layer and improve the surface quality of the underlying AlN layer.

[0043] Optionally, the thickness of the graphene layer is 50 to 500 nm.

[0044] When the thickness of the graphene layer is within the above range, it can effectively isolate the underlying AlN layer from impurities, and play a good role in covering and protecting the surface of the underlying AlN layer, improving the quality of the finally obtained light-emitting diode epitaxial wafer.

[0045] In one implementation provided by the present disclosure, the thickness of the graphene layer can be 200 nm, and the present disclosure does not limit this.

[0046] Exemplarily, in step S105, the graphene layer on the surface of the underlying AlN layer is laser-stripped.

[0047] The laser-stripping method can ensure the stable stripping of the graphene layer and ensure the surface quality of the obtained underlying AlN layer, so as to ensure the quality of epitaxial materials such as the n-type layer grown on the surface of the underlying AlN layer.

[0048] Figure 2 is a schematic structural diagram of a light-emitting diode epitaxial wafer provided by an embodiment of the present disclosure. Figure 2 The light-emitting diode epitaxial wafer provided therein is prepared by using the light-emitting diode epitaxial wafer preparation method shown in Figure 1 As shown in, it can be known that the light-emitting diode epitaxial wafer may include a substrate 1 and a underlying AlN layer 2, an n-type layer 3, a light-emitting layer 4, and a p-type layer 5 stacked on the substrate 1 in sequence. Figure 2 It should be noted that the n-type layer 3, the light-emitting layer 4, and the p-type layer 5 can be prepared by using gallium nitride materials, aluminum gallium nitride materials, or indium gallium phosphide, and the present disclosure does not limit this.

[0049]

[0050] Figure 2 The structure of the light-emitting diode epitaxial wafer provided in Figure 1 is only for illustration, The method for preparing a light-emitting diode epitaxial wafer with improved crystal quality shown in

[0051] In one implementation provided by the present disclosure, Figure 2The obtained basic AlN layer obtained as above has no cracks under optical microscope detection; has an atomically flat surface under atomic force microscope detection; the half-width of the basic AlN layer in the (002) direction measured by an X-ray diffraction detector is 150 arcsec, and the half-width in the (102) direction is 320 arcsec. Among them, (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 (002) half-width value represents screw dislocations, while the (102) half-width value represents edge dislocations. It can be seen that there are fewer defects in the overall obtained basic AlN layer.

[0052] Figure 3 It is a flowchart of another method for preparing a light-emitting diode epitaxial wafer to improve crystal quality provided by an embodiment of the present disclosure. Refer to Figure 3 It can be seen that

[0053] S201: Provide a substrate.

[0054] Among them, the substrate can be one of sapphire, silicon carbide, zinc oxide or quartz glass. It is easy to implement and manufacture.

[0055] S202: Deposit a basic AlN layer on the substrate.

[0056] Optionally, a physical vapor deposition device is used to deposit a basic AlN layer on the substrate, and the deposition temperature of the basic AlN layer is 550 - 650 °C.

[0057] Under the condition that the temperature is in the above range, the physical vapor deposition device can deposit a relatively flat and less stressed basic AlN layer on the substrate to improve the quality of epitaxial materials such as the n-type layer deposited and grown on the surface of the basic AlN layer.

[0058] In other implementation manners provided by the present disclosure, the deposition temperature of the basic AlN layer can also be 600 °C, and the present disclosure does not limit this.

[0059] Exemplarily, the deposition pressure of the basic AlN layer is 50 - 200 mbar. The quality of the obtained basic AlN layer can be improved.

[0060] Exemplarily, the thickness of the basic AlN layer is 10 - 500 nm.

[0061] When the thickness of the basic AlN layer is within the above range, the role of the basic AlN layer in alleviating lattice mismatch can be ensured, and the quality of the basic AlN layer itself can also be ensured.

[0062] In other implementation manners provided by the present disclosure, the thickness of the basic AlN layer can also be 200 nm, and the present disclosure does not limit this.

[0063] S203: Deposit a graphene layer on the base AlN layer.

[0064] Step S203 can refer to Figure 1 Step S103 in, so it will not be elaborated here.

[0065] S204: Anneal the base AlN layer.

[0066] Optionally, anneal the base AlN layer under the condition that the temperature is 1600 - 1800 °C.

[0067] Annealing the base AlN layer under the above temperature condition can ensure sufficient annealing of the base AlN layer and improve the quality of the obtained base AlN layer.

[0068] Optionally, anneal the base AlN layer for 2.5 - 3.5 h under the condition that the temperature is 1600 - 1800 °C.

[0069] With the annealing duration within the above range, it can ensure sufficient annealing of the base AlN layer and guarantee the quality of the base AlN layer.

[0070] Exemplarily, the annealing pressure of the base AlN layer can be 100 - 600 Torr. It can ensure the annealing effect.

[0071] S205: Peel off the graphene layer on the surface of the base AlN layer.

[0072] Step S205 can refer to Figure 1 Step S105 in, so it will not be elaborated here.

[0073] S206: Grow an AlN transition layer on the base AlN layer.

[0074] Growing an AlN transition layer on the surface of the relatively flat base AlN layer, the AlN transition layer itself can play a certain transition role, improving the quality of the AlN transition layer while controlling the quality of epitaxial materials such as the n-type layer grown on the AlN transition layer.

[0075] Optionally, the thickness of the AlN transition layer is 1.5 - 2.5 microns.

[0076] With the thickness of the AlN transition layer within the above range, it can improve the quality of the AlN transition layer and epitaxial materials such as the n-type layer grown on the AlN transition layer.

[0077] Optionally, the growth temperature of the AlN transition layer is 1300 - 1400 °C. Ensure the quality of the obtained AlN transition layer.

[0078] In an implementation provided by the present disclosure, an AlN transition layer with a thickness of 2000 nm can also be grown under the conditions of a temperature of 1350 °C and a growth pressure of 50 mbar. Ammonia and trimethylaluminum are introduced as reactants during the growth of the AlN transition layer, and the V / III molar ratio of ammonia to trimethylaluminum is 300. The growth time of the AlN transition layer is 5000 s. This can ensure the quality of the obtained AlN transition layer. The present disclosure places no restrictions on this.

[0079] S207: Grow an n-type layer on the AlN transition layer.

[0080] Optionally, the n-type layer is an Si-doped n-type AlGaN layer. It is easy to prepare and obtain.

[0081] Optionally, the growth temperature of the n-type AlGaN layer is 1000 °C - 1200 °C, and the pressure is 50 - 200 torr. The obtained n-type AlGaN layer has better quality and can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0082] Exemplarily, the growth thickness of the n-type AlGaN layer is between 1 and 4.0 micrometers. This can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0083] S208: Grow a light-emitting layer on the n-type layer.

[0084] Optionally, the light-emitting layer may include a multi-quantum well structure. The light-emitting layer includes a plurality of alternately stacked GaN layers and Al x Ga 1-x GaN layers (0 < x < 0.3).

[0085] Exemplarily, the growth temperature range of the GaN layer is between 850 °C and 950 °C, and the pressure range is between 100 Torr and 300 Torr; the growth temperature of the Al x Ga 1-x GaN layer is 900 °C - 1000 °C, and the growth pressure is between 50 Torr and 200 Torr. A light-emitting layer with better quality can be obtained.

[0086] Optionally, the well thickness of the GaN layer is about 3 nm, and the barrier thickness is between 8 nm and 20 nm. The obtained light-emitting layer has better quality and reasonable cost.

[0087] S209: Grow an electron blocking layer on the light-emitting layer.

[0088] Optionally, the electron blocking layer can be a p-type Al y Ga 1-y GaN layer (0.2 < y < 0.5).

[0089] Optionally, the p-type Al y Ga1-y The growth temperature of the N layer is 900°C - 1050°C, and the pressure is 50 - 200 torr. The obtained p-type doped AlGaN layer has better quality, which can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0090] Exemplarily, the growth thickness of the p-type doped AlGaN layer is between 15 and 60 nanometers. It can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0091] S210: Grow a p-type layer on the electron blocking layer.

[0092] Optionally, the growth temperature of the p-type doped AlGaN layer is 850°C - 1050°C, and the pressure is 50 - 200 torr. The obtained p-type doped AlGaN layer has better quality, which can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0093] Exemplarily, the growth thickness of the p-type doped AlGaN layer is between 100 and 300 nanometers. It can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0094] S211: Grow a p-type contact layer on the p-type layer.

[0095] Optionally, the growth temperature of the p-type contact layer is 850°C - 1050°C, and the pressure is 100 - 600 torr. The obtained p-type contact layer has better quality.

[0096] Exemplarily, the growth thickness of the p-type contact layer is between 10 and 300 nanometers. It can improve the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0097] S212: Anneal the substrate and the n-type layer, light-emitting layer and p-type layer on the substrate.

[0098] Optionally, the annealing temperature can be 650°C - 850°C, and the time can be 5 to 15 minutes. It can release the thermal stress in the epitaxial wafer and ensure the crystal quality of the finally obtained ultraviolet light-emitting diode.

[0099] It should be noted that, in the embodiments of the present disclosure, a Veeco K465i or C4 or RB MOCVD (Metal-Organic Chemical Vapor Deposition) device is used to implement the growth method of light-emitting diodes. High-purity H2 (hydrogen) or high-purity N2 (nitrogen) or a mixed gas of high-purity H2 and high-purity N2 is used as the carrier gas, high-purity NH3 is used as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as the gallium sources, trimethylindium (TMIn) is used as the indium source, silane (SiH4) is used as the N-type dopant, trimethylaluminum (TMAl) is used as the aluminum source, and bis(cyclopentadienyl)magnesium (CP2Mg) is used as the P-type dopant.

[0100] It should be noted that, Figure 3 compared with the method for preparing a light-emitting diode for improving crystal quality described in Figure 1 and the method for preparing a light-emitting diode epitaxial wafer for improving crystal quality shown in Figure 1 the method for preparing a light-emitting diode epitaxial wafer provided in this embodiment adds the preparation of an AlN transition layer and an electron blocking layer, and details the growth conditions of all hierarchical structures in the light-emitting diode epitaxial wafer. The crystal quality of the light-emitting diode epitaxial wafer obtained can be further improved on the basis of the method for preparing a light-emitting diode epitaxial wafer shown in

[0101] Figure 4 FIG. is a schematic structural diagram of another light-emitting diode epitaxial wafer provided by the embodiments of the present disclosure. Figure 4 The light-emitting diode epitaxial wafer shown in Figure 3 can be prepared by the preparation method shown in Figure 4 Referring to

[0102] It should be noted that, Figure 4 the structure of the basic AlN layer 2 shown in Figure 2 is the same as the structure of the basic AlN layer 2 shown in

[0103] and will not be elaborated here.

[0104] Optionally, the n-type layer 3 can be an n-type AlGaN layer, and the thickness of the n-type AlGaN layer can be between 1.0 and 4.0 micrometers.

[0105] Exemplarily, the light-emitting layer 4 may be a multi-quantum well structure. The light-emitting layer 4 includes alternately stacked AlGaN barrier layers and AlGaN well layers, and the Al components in the AlGaN barrier layers and AlGaN well layers are different. The light-emitting efficiency is relatively good.

[0106] The number of AlGaN barrier layers and AlGaN well layers may be the same, and both may be 4 to 12. The obtained light-emitting layer 4 has good quality and relatively reasonable cost.

[0107] Exemplarily, the electron blocking layer 7 may be a P-type Al y Ga 1-y N layer (0.2 < y < 0.5), and the thickness of the P-type Al y Ga 1-y N layer may be between 15 nm and 60 nm. The effect of blocking electrons is relatively good.

[0108] Exemplarily, the p-type layer 5 may be a P-type doped AlGaN layer. It is convenient for preparation and acquisition.

[0109] Optionally, the thickness of the p-type layer 5 is 100 - 300 nm. The overall quality of the obtained p-type layer 5 is good.

[0110] Exemplarily, the thickness of the p-type contact layer 8 may be 100 - 300 nm. The quality of the obtained p-type contact layer 8 is good.

[0111] It should be noted that Figure 2 This is only one implementation manner of the ultraviolet light-emitting diode provided by the embodiments of the present disclosure. In other implementation manners provided by the present disclosure, the ultraviolet light-emitting diode may also be other forms of ultraviolet light-emitting diodes including a reflective layer, and the present disclosure does not limit this.

[0112] Figure 4 The epitaxial wafer structure shown in Figure 2 adds an AlN transition layer and the structure of an electron blocking layer compared with the epitaxial wafer structure shown in

[0113] As mentioned above, it is not any form of limitation to the present disclosure. Although the present disclosure has been disclosed as above through embodiments, it is not intended to limit the present disclosure. Any person skilled in the art can make some modifications or equivalent changes and modifications by using the disclosed technical content within the scope of the technical solutions of the present disclosure. However, as long as it does not depart from the content of the technical solutions of the present disclosure, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present disclosure still fall within the scope of the technical solutions of the present disclosure.

Claims

1. A method for preparing a light-emitting diode epitaxial wafer to improve crystal quality, characterized in that, The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality includes: Providing a substrate; Depositing a base AlN layer on the substrate; Depositing a graphene layer on the base AlN layer by using a chemical vapor deposition device, wherein the growth temperature of the graphene layer is 1000-1200 °C, the growth pressure of the graphene layer is 0.1-1 atm, and the growth rate of the graphene layer is 10-200 nm / s; Annealing the base AlN layer; Peeling off the graphene layer on the surface of the base AlN layer; Successively growing an n-type layer, a light-emitting layer and a p-type layer on the base AlN layer.

2. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to claim 1, wherein The thickness of the graphene layer is 50-500 nm.

3. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to claim 1, wherein, Laser-peeling off the graphene layer on the surface of the base AlN layer.

4. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to any one of claims 1 to 3, characterized in that, Depositing a base AlN layer on the substrate by using a physical vapor deposition device, wherein the deposition temperature of the base AlN layer is 550-650 °C.

5. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to claim 4, wherein The thickness of the base AlN layer is 10-500 nm.

6. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to any one of claims 1 to 3, characterized in that, Annealing the base AlN layer under the condition that the temperature is 1600-1800 °C.

7. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to claim 6, wherein Annealing the base AlN layer for 2.5-3.5 h under the condition that the temperature is 1600-1800 °C.

8. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to any one of claims 1 to 3, characterized in that The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality further includes: after peeling off the graphene layer on the surface of the base AlN layer and before successively growing an n-type layer, a light-emitting layer and a p-type layer on the base AlN layer, Growing an AlN transition layer on the base AlN layer.

9. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to claim 8, wherein The thickness of the AlN transition layer is 1.5-2.5 microns.

10. The method for preparing a light-emitting diode epitaxial wafer for improving crystal quality according to claim 8, characterized in that, The growth temperature of the AlN transition layer is 1300-1400 °C.

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