CN113481593B - Preparation method of light-emitting diode epitaxial wafer with AlN - Google Patents

Abstract

The disclosure provides a method for preparing a light-emitting diode epitaxial wafer with AlN, which belongs to the technical field of light-emitting diodes. The first AlN film and the second AlN film are alternately sputtered on the surface of the substrate to finally form an AlN buffer layer. And the target distance when sputtering the first AlN film is the first target distance, the target distance when sputtering the second AlN film is the second target distance, and the first target distance is larger than the second target distance. The thickness and uniformity of the first AlN film obtained by sputtering with a larger first target distance will be better. The smaller the second target distance, the sputtering speed of the second AlN film will be faster, and the deposition rate of the second AlN film will be improved. The internal stress of the alternately obtained first AlN film and the second AlN film is released, the overall quality of the AlN buffer layer is improved, and the growth rate of the AlN buffer layer is also increased. The crystal quality of the epitaxial wafer of the light emitting diode is effectively improved while reducing the preparation period of the epitaxial wafer of the light emitting diode.

Description

Preparation method of light-emitting diode epitaxial wafer with AlN

technical field

The present disclosure relates to the technical field of light emitting diodes, in particular to a method for preparing a light emitting diode epitaxial wafer with AlN.

Background technique

Light-emitting diodes are widely used light-emitting devices, often used in traffic lights, car interior and exterior lights, urban lighting and landscape lighting, etc., and light-emitting diode epitaxial wafers are the basic structure used to prepare light-emitting diodes. A light-emitting diode epitaxial wafer usually includes a substrate and an AlN buffer layer, an n-type GaN layer, a multi-quantum well layer and a p-type GaN layer stacked sequentially on the substrate.

The AlN buffer layer can alleviate the lattice mismatch between the n-type GaN layer and the substrate. In order to improve the crystal quality of the AlN buffer layer, the growth period of the AlN buffer layer is generally relatively long, and the quality of the finally obtained AlN buffer layer is not good enough.

Contents of the invention

The embodiment of the present disclosure provides a method for preparing a light-emitting diode epitaxial wafer with AlN, which can reduce the production cycle of the light-emitting diode epitaxial wafer and effectively improve the crystal quality of the light-emitting diode epitaxial wafer. Described technical scheme is as follows:

An embodiment of the present disclosure provides a method for preparing a light-emitting diode epitaxial wafer with AlN, and the method for preparing the light-emitting diode epitaxial wafer with AlN includes:

Provide a substrate located in the magnetron sputtering device, the surface of the target in the magnetron sputtering device is directly opposite to the surface of the substrate and parallel to each other, the surface of the target and the substrate The vertical distance between the surfaces of is the target spacing;

Alternately sputtering the first AlN film and the second AlN film on the surface of the substrate to finally form an AlN buffer layer, when sputtering the first AlN film, the target distance is the first target distance, and sputtering the first AlN film When two AlN films are used, the target distance is the second target distance, and the first target distance is greater than the second target distance;

An n-type GaN layer, a multi-quantum well layer and a p-type GaN layer are grown sequentially on the AlN buffer layer.

Optionally, the first target distance is 70 mm to 100 mm, and the second target distance is 40 mm to 70 mm.

Optionally, the absolute value of the difference between the first target distance and the second target distance is 20 mm to 50 mm.

Optionally, the thickness of the first AlN film is 0.1-5 nm.

Optionally, the thickness of the second AlN film is 2-20 nm.

Optionally, a ratio of the thickness of the second AlN film to the thickness of the first AlN film is 5-20.

Optionally, the preparation method also includes:

After the first AlN film is sputtered, the second AlN film is sputtered at an interval of 20-100 s.

Optionally, the sputtering temperature of the first AlN film is 500°C-800°C, and the sputtering pressure of the first AlN film is 4-10mtorr.

Optionally, after growing the AlN buffer layer on the substrate, before growing an n-type GaN layer on the AlN buffer layer,

Perform heat treatment on the AlN buffer layer for 10-15 minutes.

Optionally, the temperature for heat treatment of the AlN buffer layer is 1100-1200°C.

The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure include:

Put the substrate in the magnetron sputtering device, and make the surface of the target in the magnetron sputtering device face the surface of the substrate and be parallel to each other, the vertical distance between the surface of the target and the surface of the substrate is the target distance. When the AlN buffer layer needs to be sputtered on the substrate, the first AlN film and the second AlN film can be alternately sputtered on the surface of the substrate to finally form the AlN buffer layer. And the target distance when sputtering the first AlN film is the first target distance, the target distance when sputtering the second AlN film is the second target distance, and the first target distance is larger than the second target distance. The thickness and uniformity of the first AlN film obtained by sputtering with a larger first target distance will be better, and it can ensure that the quality of the second AlN film grown on the first AlN film is better. The speed of sputtering the second AlN film with the smaller second target spacing will be faster, which can improve the deposition rate of the second AlN film, and the reduction of the uniformity of the second AlN film due to the reduction of the second target spacing can be eliminated. The improvement of the quality of the first AlN film is offset, and the overall quality can still be guaranteed. The internal stress of the alternately obtained first AlN film and the second AlN film can be released, and the internal defects of the finally obtained AlN buffer layer caused by stress are less, the overall quality of the AlN buffer layer can be improved, and the AlN buffer layer The growth rate of the layers can also be increased. The crystal quality of the epitaxial wafer of the light emitting diode is effectively improved while reducing the preparation cycle of the epitaxial wafer of the light emitting diode.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

FIG. 1 is a flow chart of a method for preparing a light-emitting diode epitaxial wafer with AlN provided by an embodiment of the present disclosure;

Fig. 2 is a simplified diagram of the internal structure of a magnetron sputtering device provided by an embodiment of the present disclosure;

FIG. 3 is a schematic structural view of a light emitting diode epitaxial wafer provided by an embodiment of the present disclosure;

4 is a flow chart of another method for preparing a light-emitting diode epitaxial wafer with AlN provided by an embodiment of the present disclosure;

FIG. 5 is a schematic structural diagram of another light-emitting diode epitaxial wafer provided by an embodiment of the present disclosure.

detailed description

In order to make the purpose, technical solution and advantages of the present disclosure clearer, the implementation manners of the present disclosure will be further described in detail below in conjunction with the accompanying drawings.

Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by those having ordinary skill in the art to which the present disclosure belongs. "First", "second", "third" and similar words used in the specification and claims of this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components . Likewise, words like "a" or "one" do not denote a limitation in quantity, but indicate that there is at least one. Words such as "comprises" or "comprising" and similar terms mean that the elements or items listed before "comprising" or "comprising" include the elements or items listed after "comprising" or "comprising" and their equivalents, and do not exclude other component or object. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", "Top", "Bottom" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also be Change accordingly.

Fig. 1 is a flow chart of a method for preparing a light-emitting diode epitaxial wafer with AlN provided by an embodiment of the present disclosure. As shown in Fig. 1, the preparation method of the light-emitting diode epitaxial wafer with AlN includes:

S101: Provide a substrate located in a magnetron sputtering device, the surface of the target in the magnetron sputtering device is directly opposite to and parallel to the surface of the substrate, and the vertical distance between the surface of the target and the surface of the substrate is The distance is the target pitch.

S102: Alternately sputtering the first AlN film and the second AlN film on the surface of the substrate to finally form an AlN buffer layer, the target pitch when sputtering the first AlN film is the first target pitch, and the target pitch when sputtering the second AlN film The target pitch is the second target pitch, and the first target pitch is greater than the second target pitch.

S103: growing an n-type GaN layer, a multi-quantum well layer, and a p-type GaN layer sequentially on the AlN buffer layer.

Put the substrate in the magnetron sputtering device, and make the surface of the target in the magnetron sputtering device face the surface of the substrate and be parallel to each other, the vertical distance between the surface of the target and the surface of the substrate is the target distance. When the AlN buffer layer needs to be sputtered on the substrate, the first AlN film and the second AlN film can be alternately sputtered on the surface of the substrate to finally form the AlN buffer layer. And the target distance when sputtering the first AlN film is the first target distance, the target distance when sputtering the second AlN film is the second target distance, and the first target distance is larger than the second target distance. The thickness and uniformity of the first AlN film obtained by sputtering with a larger first target distance will be better, and it can ensure that the quality of the second AlN film grown on the first AlN film is better. The speed of sputtering the second AlN film with the smaller second target spacing will be faster, which can improve the deposition rate of the second AlN film, and the reduction of the uniformity of the second AlN film due to the reduction of the second target spacing can be eliminated. The improvement of the quality of the first AlN film is offset, and the overall quality can still be guaranteed. The internal stress of the alternately obtained first AlN film and the second AlN film can be released, and the internal defects of the finally obtained AlN buffer layer caused by stress are less, the overall quality of the AlN buffer layer can be improved, and the AlN buffer layer The growth rate of the layers can also be increased. The crystal quality of the epitaxial wafer of the light emitting diode is effectively improved while reducing the preparation cycle of the epitaxial wafer of the light emitting diode.

For ease of understanding, FIG. 2 can be provided here. FIG. 2 is a simplified diagram of the internal structure of the magnetron sputtering device provided by the embodiment of the present disclosure. Referring to FIG. 2, it can be known that the substrate 1 and the target 100 are located in the magnetron sputtering device In the cavity of the magnetron sputtering device, the substrate 1 is fixed on the top of the cavity of the magnetron sputtering device, and the target material 100 is fixed on the bottom of the cavity of the magnetron sputtering device, and the surface of the target material 100 is a plane, and the surface of the target material 100 and The surfaces of the substrate 1 are opposite and parallel to each other, and the target distance is marked as C in FIG. 2 .

FIG. 3 is a schematic structural view of a light emitting diode epitaxial wafer provided by an embodiment of the present disclosure. Referring to FIG. 3, it can be known that an embodiment of the present disclosure provides a light emitting diode epitaxial wafer. AlN buffer layer 2, n-type GaN layer 3, multi-quantum well layer 4 and p-type GaN layer 5 on the bottom 1.

It should be noted that the structure of the light-emitting diode epitaxial wafer provided in Figure 3 is only for illustration, and the preparation method of the light-emitting diode epitaxial wafer with AlN shown in Figure 1 can also be applied to other light-emitting diodes with more layers Epitaxial wafer, the present disclosure does not limit it.

FIG. 4 is a flow chart of another method for preparing a light emitting diode epitaxial wafer with AlN provided by an embodiment of the present disclosure. As shown in FIG. 4 , the preparation method of the light emitting diode epitaxial wafer with AlN includes:

S201: Provide a substrate.

Wherein, the substrate may be a sapphire substrate. Easy to implement and make.

S202: Put the substrate into the magnetron sputtering device, the surface of the target in the magnetron sputtering device is facing the surface of the substrate and parallel to each other, the vertical distance between the surface of the target and the surface of the substrate is the target distance.

Optionally, step S202 may further include: treating the surface of the substrate for growing the epitaxial layer for 5-6 minutes in a hydrogen atmosphere.

Exemplarily, when the substrate is processed to grow the surface of the epitaxial layer, the temperature of the reaction chamber may be 1000-1100° C., and the pressure of the reaction chamber may be 200-500 torr. Impurities existing on the substrate can be effectively removed to ensure better quality of the finally obtained epitaxial structure on the substrate.

S203: Alternately sputtering the first AlN film and the second AlN film on the surface of the substrate to finally form an AlN buffer layer, the target pitch when sputtering the first AlN film is the first target pitch, and the target pitch when sputtering the second AlN film The target pitch is the second target pitch, and the first target pitch is greater than the second target pitch.

Optionally, the growth thickness of the AlN buffer layer may be 10-50 nm.

The growth thickness of the AlN buffer layer within the above range can effectively improve the crystal quality of the finally obtained AlN buffer layer and ensure the quality of the epitaxial material grown on the AlN buffer layer.

Optionally, the sputtering temperature of the first AlN film is 500° C.˜800° C., and the sputtering pressure of the first AlN film is 4˜10 mtorr.

When the sputtering temperature and sputtering pressure of the first AlN film are within the above range, the first AlN film with good quality can be obtained.

Exemplarily, the sputtering temperature of the second AlN film is the same as that of the first AlN film, and the sputtering pressure of the second AlN film is the same as that of the first AlN film. The method can ensure good quality of the finally obtained AlN buffer layer and effectively improve the forming efficiency of the AlN buffer layer.

Exemplarily, the first target distance is 70 mm to 100 mm, and the second target distance is 40 mm to 70 mm.

When the first target distance and the second target distance are within the above range, the quality of the obtained first AlN film and the second AlN film will be better, and the deposition efficiency of the first AlN film and the second AlN film will be higher, The preparation period of the epitaxial wafer of the light emitting diode can be effectively reduced while the crystal quality of the epitaxial wafer of the light emitting diode can be improved.

Optionally, the absolute value of the difference between the first target distance and the second target distance is 20 mm to 50 mm.

If the absolute value of the difference between the first target distance and the second target distance is within the above range, the quality gap between the first AlN film and the second AlN film can be controlled to be small, and the quality of the final AlN buffer layer can be guaranteed. The growth efficiency of the layer is also high, and the growth time of the AlN buffer layer can be shortened.

Optionally, the sputtering duration of the first AlN film is 2-20s, and the sputtering duration of the second AlN film is equal to the sputtering duration of the first AlN film.

The sputtering duration of the first AlN film is 2-20s, and the sputtering duration of the second AlN film is equal to the sputtering duration of the first AlN film, which can effectively improve the quality of the first AlN film and the second AlN film, and improve the growth rate.

Exemplarily, the thickness of the first AlN film is 0.1-5 nm.

The thickness of the first AlN film is in the above range, which can ensure that the quality of the first AlN film obtained is better, and can transition to the second AlN film well, so that the second AlN film grown on the first AlN film can also have a relatively good quality. improve the quality of the final AlN buffer layer.

Optionally, the thickness of the second AlN film is 2-20 nm.

The thickness of the second AlN film is in the above range, which can ensure that the quality of the second AlN film obtained is better, and the quality of the first AlN film grown on the second AlN film will also be better, improving the final obtained AlN buffer layer. the quality of. When the thickness of the first AlN film and the thickness of the second AlN film are respectively in the above ranges, it can also be ensured that when the first AlN film and the second AlN film grow alternately, the internal stress can offset most of them, so as to improve the final obtained The quality of the AlN buffer layer.

It should be noted that in the process of alternate sputtering, the thickness of the AlN buffer layer will actually increase slowly. Therefore, in the subsequent sputtering, although the first target distance and the second target distance remain unchanged, the distance between the target material and the AlN material The distance actually decreases to a certain extent, so after alternately growing the first AlN film and the second AlN film multiple times, the growth rates of the first AlN film and the second AlN film will both increase slightly, further reducing the first AlN film. The time required for the growth of the AlN film and the second AlN film. However, when the thickness of the first AlN film and the second AlN film have a certain thickness, the quality of the first AlN film and the second AlN film will not be affected by a slight increase in sputtering speed.

Optionally, the ratio of the thickness of the second AlN film to the thickness of the first AlN film is 5-20.

If the ratio of the thickness of the second AlN film to the thickness of the first AlN film is within the above range, the quality of the finally obtained AlN buffer layer is better.

In an implementation manner provided in the present disclosure, step S203 may further include:

After the first AlN film is sputtered, the second AlN film is sputtered at an interval of 20 to 100 s.

After the first AlN film is sputtered, the second AlN film is sputtered after an interval of more than a certain period of time can be used to adjust the position of the target in the magnetron sputtering device, and within this time, the first AlN film There is also time to release internal stresses, improving the quality of the resulting AlN buffer.

Exemplarily, after the second AlN film is sputtered, the first AlN film may be sputtered again at an interval of 20-100 s. It is also possible to increase the quality of the second AlN film to increase the quality of the AlN buffer.

Optionally, during the sputtering process of the first AlN film and the second AlN film, the gas introduced into the magnetron sputtering device includes argon, nitrogen and oxygen.

The above gas is passed into the sputtering process of the first AlN film and the second AlN film, which can effectively reduce the internal defects of the first AlN film and the second AlN film, and improve the crystallinity of the first AlN film and the second AlN film finally obtained. quality.

Exemplarily, during the sputtering process of the first AlN film and the second AlN film, the flow rate of argon gas fed into the magnetron sputtering device is 30-100 sccm, the flow rate of nitrogen gas is 100-200 sccm, and the flow rate of oxygen gas is 1～5 sccm. The first AlN film and the second AlN film with better quality can be obtained.

In an implementation manner provided in the present disclosure, the flow rate of the argon gas is 50 sccm, the flow rate of the nitrogen gas is 150 sccm, and the flow rate of the oxygen gas is 2 sccm. The first AlN film and the second AlN film with better quality can be obtained.

In an implementation manner provided by the present disclosure, the sum of the sputtering times of the first AlN film and the sputtering times of the second AlN film may be 3-10 times.

The sum of the sputtering times of the first AlN film and the sputtering times of the second AlN film is 3-10 times, which can ensure that the quality of the finally obtained AlN buffer layer is better.

In an implementation manner provided by the present disclosure, the sum of the sputtering times of the first AlN film and the sputtering times of the second AlN film may be three. The growth period can be reduced while improving the quality of the AlN buffer layer.

S204: performing heat treatment on the AlN buffer layer for 10-15 minutes.

The above-mentioned length of heat treatment on the grown AlN buffer layer can remove residual impurities on the AlN buffer layer, improve the surface quality of the AlN buffer layer, and improve the quality of the epitaxial material grown on the AlN buffer layer.

Optionally, the temperature for heat treatment of the AlN buffer layer is 1100-1200°C.

The heat treatment temperature of the AlN buffer layer is in the above range, and impurities can be effectively removed.

Exemplarily, the AlN buffer layer is heat-treated in a hydrogen atmosphere. Can effectively remove impurities.

S205: growing a GaN buffer layer on the AlN buffer layer.

Exemplarily, the growth temperature of the GaN buffer layer may be 530-560° C., and the pressure may be 200-500 mtorr. The quality of the obtained GaN buffer layer is better.

S206: growing a non-doped GaN layer on the GaN buffer layer.

The thickness of the non-doped GaN layer may be 0.5-3um.

Exemplarily, the growth temperature of the non-doped GaN layer may be 1000-1100° C., and the growth pressure may be controlled at 100-300 torr. The quality of the obtained undoped GaN layer is better.

S207: growing an n-type GaN layer on the non-doped GaN layer.

Optionally, the growth temperature of the n-type GaN layer may be 1000-1100° C., and the growth pressure of the n-type GaN layer may be 100-300 Torr.

Optionally, the thickness of the n-type GaN layer may be 0.5-3um.

S208: growing multiple quantum well layers on the n-type GaN layer. The multiple quantum well layer includes alternately grown well layers and GaN barrier layers.

Exemplarily, the growth temperature of the well layer may be 700-830°C. The growth temperature of the GaN barrier layer is 800-960°C. A multi-quantum well layer with better quality can be obtained.

S209: growing an electron blocking layer on the multiple quantum well layer.

The electron blocking layer may be an AlGaN electron blocking layer, the growth temperature of the AlGaN electron blocking layer may be 800-1000° C., and the growth pressure of the AlGaN electron blocking layer may be 100-300 Torr. The quality of the AlGaN electron blocking layer grown under this condition is better, which is conducive to improving the luminous efficiency of the light emitting diode.

S210: growing a p-type GaN layer on the electron blocking layer.

Optionally, the growth pressure of the p-type GaN layer may be 200-600 Torr, and the growth temperature of the p-type GaN layer may be 800-1000°C.

S211: growing a p-type contact layer on the p-type GaN layer.

Optionally, the growth pressure of the p-type contact layer may be 100-300 Torr, and the growth temperature of the p-type contact layer may be 800-1000°C.

It should be noted that the preparation method of the LED epitaxial wafer with AlN shown in FIG. 5 provides a more detailed growth method of the LED epitaxial wafer compared with the preparation method of the LED shown in FIG. 1 .

It should be noted that, in the embodiments of the present disclosure, VeecoK 465i or C4 or RB MOCVD (MetalOrganic Chemical Vapor Deposition, metal organic compound chemical vapor deposition) equipment is used to realize the growth method of light emitting diodes. Use high-purity H ₂ (hydrogen) or high-purity N ₂ (nitrogen) or a mixture of high-purity H ₂ and high-purity N ₂ as carrier gas, high-purity NH ₃ as N source, trimethylgallium (TMGa) and three Ethyl gallium (TEGa) as gallium source, trimethyl indium (TMIn) as indium source, silane (SiH4) as N-type dopant, trimethyl aluminum (TMAl) as aluminum source, dimagnesocene (CP ₂ Mg ) as a P-type dopant.

The structure of the light emitting diode epitaxial wafer after step S211 can be referred to FIG. 5 .

FIG. 5 is a schematic structural view of another light-emitting diode epitaxial wafer provided by an embodiment of the present disclosure. Referring to FIG. AlN buffer layer 2, GaN buffer layer 6, non-doped GaN layer 7, n-type GaN layer 3, multiple quantum well layer 4, electron blocking layer 8, p-type GaN layer 5 and p-type contact layer 9 on the bottom 1.

The structure of the AlN buffer layer 2 shown in FIG. 5 may refer to the structure of the AlN buffer layer 2 shown in FIG. 3 , so details are not repeated here.

Optionally, the GaN buffer layer 6 may have a thickness of 10-30 nm. The lattice mismatch between the n-type GaN layer and the substrate 1 can be reduced to ensure the crystal quality of the epitaxial layer.

Exemplarily, the thickness of the non-doped GaN layer 7 may be 1-3.5 μm. The quality of the light emitting diode epitaxial wafer obtained at this time is relatively good.

Optionally, the doping element of the n-type GaN layer 3 may be Si, and the doping concentration of the Si element may be 1×10 ¹⁸ to 1×10 ¹⁹ cm ⁻³ . The overall quality of the n-type GaN layer 3 is relatively good.

Exemplarily, the thickness of the n-type GaN layer 3 may be 2˜3 μm. The overall quality of the obtained n-type GaN layer is good.

Optionally, the multi-quantum well layer 4 may include alternately stacked well layers 41 and GaN barrier layers 42 . Easy to prepare and obtain.

Optionally, the Al composition in the electron blocking layer 8 may be 0.15-0.25. The effect of blocking electrons is better.

Optionally, the p-type GaN layer 5 can be doped with Mg.

Exemplarily, the thickness of the p-type contact layer 9 may be 15 nm.

It should be noted that, compared with the epitaxial wafer structure shown in FIG. 3, the epitaxial wafer structure shown in FIG. 5 has an electron blocking layer 8 added between the multi-quantum well layer 4 and the p-type GaN layer 5. A p-type contact layer 9 is also grown on layer 5 . The quality and luminous efficiency of the obtained epitaxial wafer will be better.

The above description does not limit the present invention in any form. Although the present invention has been disclosed above through the embodiments, it is not used to limit the present invention. When the technical content disclosed above can be used to make some changes or be modified into equivalent embodiments with equivalent changes, any simple modifications made to the above embodiments according to the technical essence of the present invention, Equivalent changes and modifications still fall within the scope of the technical solution of the present invention.

Claims (9)

1. a method for preparing a light-emitting diode epitaxial wafer with AlN, characterized in that, the preparation method of the light-emitting diode epitaxial wafer with AlN comprises: Provide a substrate located in the magnetron sputtering device, the surface of the target in the magnetron sputtering device is directly opposite to the surface of the substrate and parallel to each other, the surface of the target and the substrate The vertical distance between the surfaces of is the target spacing; Alternately sputtering a first AlN film and a second AlN film on the surface of the substrate to finally form an AlN buffer layer, the interval between sputtering the first AlN film and sputtering the second AlN film is 20-100s, When sputtering the first AlN film, the target spacing is the first target spacing, when sputtering the second AlN film, the target spacing is the second target spacing, and the first target spacing is larger than the second target spacing spacing, the sputtering temperature of the first AlN film is 500°C to 800°C, and the sputtering temperature of the second AlN film is the same as the sputtering temperature of the first AlN film; An n-type GaN layer, a multi-quantum well layer and a p-type GaN layer are grown sequentially on the AlN buffer layer. 2 . The method for preparing a light-emitting diode epitaxial wafer with AlN according to claim 1 , wherein the first target distance is 70 mm to 100 mm, and the second target distance is 40 mm to 70 mm. 3 . 3 . The method for preparing a light-emitting diode epitaxial wafer with AlN according to claim 1 , wherein the absolute value of the difference between the first target distance and the second target distance is 20 mm to 50 mm. 4 . 4. The method for preparing a light-emitting diode epitaxial wafer with AlN according to any one of claims 1-3, characterized in that the thickness of the first AlN film is 0.1-5 nm. 5 . The method for preparing a light emitting diode epitaxial wafer with AlN according to any one of claims 1 to 3 , characterized in that the thickness of the second AlN film is 2 to 20 nm. 6. The method for preparing a light-emitting diode epitaxial wafer with AlN according to any one of claims 1 to 3, wherein the ratio of the thickness of the second AlN film to the thickness of the first AlN film is 5 ~20. 7. The method for preparing a light-emitting diode epitaxial wafer with AlN according to any one of claims 1 to 3, characterized in that, The sputtering pressure of the first AlN film is 4-10 mtorr. 8. The method for preparing a light-emitting diode epitaxial wafer with AlN according to any one of claims 1 to 3, characterized in that, after growing an AlN buffer layer on the substrate, grow n on the AlN buffer layer. type GaN layer before the Perform heat treatment on the AlN buffer layer for 10-15 minutes. 9 . The method for preparing a light-emitting diode epitaxial wafer with AlN according to claim 8 , wherein the temperature for heat treatment of the AlN buffer layer is 1100-1200° C.

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