CN113284801B - Preparation method of gallium nitride-based high electron mobility transistor epitaxial wafer - Google Patents

Abstract

The disclosure provides a method for preparing a gallium nitride-based high electron mobility transistor epitaxial wafer, which belongs to the field of semiconductor technology. The preparation method includes: providing a substrate; growing a nucleation layer on the substrate, performing a first high-temperature corrosion treatment on the nucleation layer during the growth of the nucleation layer; growing a high-resistance buffer layer on the nucleation layer, In the process of growing the high-resistance buffer layer, the high-resistance buffer layer is sequentially subjected to a second high-temperature corrosion treatment and ion beam bombardment treatment; a channel layer and an AlGaN barrier layer are sequentially grown on the high-resistance buffer layer. The preparation method can effectively avoid the stress and defect extension caused by lattice mismatch in the epitaxial layer, improve the crystal quality of the finally formed epitaxial layer, and improve the electron mobility of the electron mobility transistor.

Description

Preparation method of gallium nitride-based high electron mobility transistor epitaxial wafer

technical field

The disclosure relates to the technical field of semiconductors, in particular to a method for preparing gallium nitride-based high electron mobility transistor epitaxial wafers.

Background technique

HEMT (High Electron Mobility Transistor, High Electron Mobility Transistor) is a type of FET (Field Effect Transistor, Field Effect Transistor), which uses two materials with different energy gaps to form a heterojunction to provide a channel for carriers. GaN (gallium nitride)-based materials have the characteristics of wide band gap, high electron mobility, high voltage resistance, radiation resistance, easy formation of heterostructures, and large spontaneous polarization effect, and are suitable for the preparation of semiconductor devices such as HEMTs.

In the related art, a GaN-based HEMT includes an epitaxial layer and a source, a drain, and a gate respectively disposed on the epitaxial layer. The source and the drain form an ohmic contact with the epitaxial layer, and a ohmic contact is formed between the gate and the epitaxial layer. Teki contacts. The epitaxial layer includes a substrate and a channel layer and a barrier layer sequentially stacked on the substrate, and a two-dimensional electron gas with high concentration and high mobility is formed at the heterojunction interface of the channel layer and the barrier layer.

The material of the substrate is sapphire or silicon carbide, and the material of the channel layer is GaN. There is a large lattice mismatch between the substrate and the channel layer, and the stress and defects caused by the lattice mismatch extend and form in the epitaxial layer. Accumulation, resulting in poor crystal quality of the epitaxial layer, affecting the mobility of carriers.

Contents of the invention

The embodiment of the present disclosure provides a method for preparing a gallium nitride-based high electron mobility transistor epitaxial wafer, which can effectively avoid stress and defect extension caused by lattice mismatch in the epitaxial layer, and improve the crystal quality of the finally formed epitaxial layer. And improve the electron mobility of the electron mobility transistor. Described technical scheme is as follows:

An embodiment of the present disclosure provides a method for preparing a gallium nitride-based high electron mobility transistor epitaxial wafer, the preparation method comprising:

providing a substrate;

growing a nucleation layer on the substrate, and performing a first high-temperature corrosion treatment on the nucleation layer during the process of growing the nucleation layer;

growing a high-resistance buffer layer on the nucleation layer, and sequentially performing a second high-temperature corrosion treatment and ion beam bombardment treatment on the high-resistance buffer layer during the process of growing the high-resistance buffer layer;

A channel layer and an AlGaN barrier layer are grown sequentially on the high-resistance buffer layer.

Optionally, during the process of growing the nucleation layer, performing a first high-temperature corrosion treatment on the nucleation layer includes:

growing the first nucleation layer;

Soaking the first nucleation layer in hot alkali solution for a first set time;

Spinning and drying the first nucleation layer after soaking with deionized water;

A second nucleation layer is grown on the first nucleation layer.

Optionally, the growing the first nucleation layer includes:

Control the temperature of the reaction chamber to be 600-950°C and the pressure to be 100-300mbar to grow the first nucleation layer, the thickness of the first nucleation layer being 1/3-1/2 of the total thickness of the nucleation layer .

Optionally, soaking the first nucleation layer in hot alkali solution for a first set time includes:

Soaking the first nucleation layer in a hot alkali solution with a KOH or NaOH concentration of 20% to 50% and a temperature of 30 to 60°C for 15 to 35 minutes.

Optionally, said drying the soaked first nucleation layer with deionized water, including:

Put the soaked first nucleation layer into an oven, and dry it for 20-60min at 50-150°C and vacuum degree of -500--720pa.

Optionally, during the process of growing the high-resistance buffer layer, sequentially performing a second high-temperature etching treatment and ion beam bombardment treatment on the high-resistance buffer layer, including:

growing a first high-resistance buffer layer;

Soaking the first high-resistance buffer layer in hot alkali solution for a second set time;

Spinning and drying the first high-resistance buffer layer after soaking with deionized water;

growing a second high resistance buffer layer on the first high resistance buffer layer;

performing ion beam bombardment on the second high-resistance buffer layer;

growing a third high resistance buffer layer on the second high resistance buffer layer.

Optionally, the growing the first high-resistance buffer layer includes:

controlling the temperature of the reaction chamber to be 1000-1200° C., and the pressure to be 100-300 mbar to grow the first high-resistance buffer layer, and the thickness of the first high-resistance buffer layer is 1/2 to 1/2 of the total thickness of the high-resistance buffer layer. 2/3.

Optionally, said soaking said first high-resistance buffer layer in hot alkali solution for a second set time includes:

Soak the first high-resistance buffer layer in a hot alkali solution with a concentration of KOH or NaOH of 20%-50% and a temperature of 30-60° C. for 15-35 minutes.

Optionally, the growing the second high-resistance buffer layer on the first high-resistance buffer layer includes:

The temperature of the reaction chamber is controlled to be 1000-1200° C. and the pressure is 100-300 mbar to grow the second high-resistance buffer layer, and the thickness of the second high-resistance buffer layer is 100-200 nm.

Optionally, performing ion beam bombardment on the second high-resistance buffer layer includes:

Using the ion source mixed with C and Ar, under the vacuum condition of 10 ^-7 ~ 10 ^-5 Pa, the ion beam current generated by the ion source is controlled to be 20 ~ 150mA, the energy is 5 ~ 30KeV, and the power is 5 ~ 20kw, accelerating and focusing the ion beam so that the ion beam bombards the second high-resistance buffer layer.

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

By forming a nucleation layer on the substrate before growing the GaN channel layer on the substrate, and performing the first high-temperature corrosion treatment on the nucleation layer during the formation of the nucleation layer, it is possible to form on the nucleation layer Porous structure, the relaxation formed by porous GaN can effectively release the piezoelectric stress formed by the AlGaN high-resistance buffer layer, improve the crystal quality of the bottom layer, and thus help to obtain a channel layer with higher mobility and a two-dimensional electron gas interface. At the same time, after the growth of the nuclear layer is completed, in the process of growing the high-resistance buffer layer, the high-resistance buffer layer is subjected to a second high-temperature corrosion treatment, so that pores can be further formed on the high-resistance buffer layer. The air in between is non-conductive and can form a high-resistance film to increase impedance and reduce the influence of background carriers on the channel. Then, ion beam bombardment treatment is performed on the high-resistance buffer layer, which is conducive to the formation of uniform dangling bonds on the surface, and maintains the uniformity and consistency of the chemical bonding state, so that the stress extending and accumulating in the epitaxial layer is generally reduced, and the defects are reduced. The crystal quality of the layer is improved, and the electron mobility of the high electron mobility transistor is higher.

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 flowchart of a method for preparing a gallium nitride-based high electron mobility transistor epitaxial wafer provided by an embodiment of the present disclosure;

FIG. 2 is a flow chart of another method for preparing GaN-based high electron mobility transistor epitaxial wafers provided by an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of a gallium nitride-based high electron mobility transistor epitaxial wafer provided by an embodiment of the present disclosure.

Detailed ways

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.

Fig. 1 is a flow chart of a method for preparing a gallium nitride-based high electron mobility transistor epitaxial wafer provided by an embodiment of the present disclosure. As shown in Fig. 1 , the preparation method includes:

Step 101, providing a substrate.

Exemplarily, the substrate may be a sapphire, Si or SiC substrate.

Step 102, growing a nucleation layer on the substrate, and performing a first high-temperature corrosion treatment on the nucleation layer during the process of growing the nucleation layer.

Wherein, the nucleation layer is a GaN layer.

Step 103 , growing a high-resistance buffer layer on the nucleation layer. During the process of growing the high-resistance buffer layer, performing a second high-temperature corrosion treatment and ion beam bombardment treatment on the high-resistance buffer layer in sequence.

Wherein, the high-resistance buffer layer is an AlGaN layer.

Step 104, growing a channel layer and an AlGaN barrier layer sequentially on the high-resistance buffer layer.

Wherein, the channel layer is a GaN layer. The channel layer is a transport channel for the two-dimensional electron gas, and requires a smooth surface and low doping concentration to reduce the scattering of the two-dimensional electron gas.

The AlGaN barrier layer will generate a large amount of positive polarization charges at the interface between the barrier layer and the channel layer through its own large white hair polarization or piezoelectric polarization, and the polarized positive charges can attract electrons. Thus a two-dimensional electron gas is formed.

In the embodiments of the present disclosure, a nucleation layer is first formed on the substrate before the GaN channel layer is grown on the substrate. A porous structure is formed on the core layer, and the relaxation formed by porous GaN can effectively release the piezoelectric stress formed by the AlGaN high-resistance buffer layer and improve the crystal quality of the bottom layer, which is conducive to obtaining a channel layer with higher mobility and two-dimensional electrons. air interface. At the same time, after the growth of the nuclear layer is completed, in the process of growing the high-resistance buffer layer, the high-resistance buffer layer is subjected to a second high-temperature corrosion treatment, so that pores can be further formed on the high-resistance buffer layer. The air in between is non-conductive and can form a high-resistance film to increase impedance and reduce the influence of background carriers on the channel. Then, ion beam bombardment treatment is performed on the high-resistance buffer layer, which is conducive to the formation of uniform dangling bonds on the surface, and maintains the uniformity and consistency of the chemical bonding state, so that the stress extending and accumulating in the epitaxial layer is generally reduced, and the defects are reduced. The crystal quality of the layer is improved, and the electron mobility of the high electron mobility transistor is higher.

Fig. 2 is a flow chart of another GaN-based high electron mobility transistor epitaxial wafer preparation method provided by an embodiment of the present disclosure. As shown in Fig. 2 , the preparation method includes:

Step 201, providing a substrate.

Exemplarily, the substrate may be a sapphire, Si or SiC substrate.

It should be noted that, in this embodiment, a nucleation layer, a high-resistance buffer layer, a channel layer, and an AlGaN barrier can be sequentially grown on the substrate by MOCVD (Metal organic Chemic alVaporDeposition, metal organic compound chemical vapor deposition method) layer. The temperature and pressure controlled during the growth actually refer to the temperature and pressure in the reaction chamber of the MOCVD equipment.

Exemplarily, high-purity NH ₃ is used as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as the gallium source, and trimethylaluminum (TMAl) is used as the aluminum source.

Exemplarily, step 401 may also include:

The substrate is subjected to a high temperature _H2O annealing treatment.

The annealing treatment method includes: treating the substrate at a high temperature for 6-10 minutes in a hydrogen (as carrier gas) atmosphere in a reaction chamber of the MOCVD equipment. Wherein, the temperature of the reaction chamber is 1000-1100° C., and the pressure of the reaction chamber is controlled at 200-500 torr.

Step 202, growing a nucleation layer on the substrate.

Wherein, the nucleation layer is a GaN layer with a thickness of 80-150 nm.

Exemplarily, step 202 may include:

The first step is to grow the first nucleation layer.

Optionally, the first step includes:

The temperature of the reaction chamber is controlled to be 600-950° C. and the pressure is 100-300 mbar to grow the first nucleation layer.

Wherein, the thickness of the first nucleation layer is 1/3˜1/2 of the total thickness of the nucleation layer.

If the thickness of the first nucleation layer is too thin, it is difficult to effectively improve the crystallization behavior of the epitaxial layer, and the crystal quality is less affected. If the thickness of the first nucleation layer is too thick, a thicker epitaxial layer will be required for filling. At the same time, due to the excessive treatment depth, semipolar plane growth will be introduced, which may lead to abnormal surface morphology of the epitaxial layer.

The second step is soaking the first nucleation layer in hot alkali solution for a first set time.

Optionally, the second step includes:

Soak the first nucleation layer in a hot alkali solution with a KOH or NaOH concentration of 20% to 50% and a temperature of 30 to 60° C. for 15 to 35 minutes.

In the embodiment of the present disclosure, the first set time is 15-35 minutes.

If the first setting time is too long, the etching depth will be too thick. On the one hand, a thicker epitaxial layer is required to fill it up. On the other hand, it will introduce the growth of semi-polar planes, resulting in abnormal surface morphology of the epitaxial layer. If the first setting time is too short, the etching depth will be shallow, and it is difficult to affect the crystal quality of the epitaxial layer.

The third step is drying the soaked first nucleation layer with deionized water.

Optionally, the third step includes:

Put the soaked first nucleation layer into an oven, and dry it for 20-60min at 50-150°C and vacuum degree of -500--720pa.

Step 4, growing a second nucleation layer on the first nucleation layer.

Optionally, the fourth step includes:

The temperature of the reaction chamber is controlled to be 600-950° C. and the pressure is 100-300 mbar to grow the second nucleation layer.

In this step, by first growing the first nucleation layer with a certain thickness, and then performing high-temperature corrosion treatment on the first nucleation layer, the extension of dislocation and stress introduced by the difference in lattice constant between the substrate and gallium nitride can be improved, and the Crystalline quality of the nucleation layer.

Step 203 , performing an in-situ annealing treatment on the nucleation layer.

Exemplarily, the temperature of the reaction chamber is controlled at 1000° C. to 1200° C., the pressure is 100 to 300 mbar, and the nucleation layer is annealed in situ for 5 minutes to 10 minutes.

Step 204, growing a high-resistance buffer layer on the nucleation layer.

Wherein, the high-resistance buffer layer is an AlGaN layer with a thickness of 1-3um.

Exemplarily, step 204 may include:

The first step is to grow the first high-resistance buffer layer.

Optionally, the first step includes:

The temperature of the reaction chamber is controlled to be 1000-1200° C. and the pressure is 100-300 mbar to grow the first high-resistance buffer layer.

Wherein, the thickness of the first high-resistance buffer layer is 1/2˜2/3 of the total thickness of the high-resistance buffer layer.

If the thickness of the first high-resistance buffer layer is too thin, it is difficult to play the role of stress release; if the thickness of the first high-resistance buffer layer is too thick, the thickness of the high-resistance buffer layer will be thinner and the process window will be narrower. Difficulty maintaining stability and repeatability.

The second step is soaking the first high-resistance buffer layer in hot alkali solution for a second set time.

Optionally, the second step includes:

Soak the first high-resistance buffer layer in a hot alkali solution with a KOH or NaOH concentration of 20% to 50% and a temperature of 30 to 60°C for 15 to 35 minutes.

In the embodiment of the present disclosure, the second set time is 15-35 minutes.

If the second setting time is too long, the etching depth will be too large, and too many micro-defects will appear, which will affect the device performance of the light emitting diode. If the second setting time is too short, it will be difficult to effectively improve the crystal quality of the high-resistance buffer layer.

In the third step, the soaked first high-resistance buffer layer is dried with deionized water.

Optionally, the third step includes:

Put the soaked first high-resistance buffer layer into an oven, and dry it for 20-60 minutes at 50-150°C and vacuum degree of -500--720pa.

Step 4, growing a second high-resistance buffer layer on the first high-resistance buffer layer.

Optionally, the fourth step includes:

The temperature of the reaction chamber is controlled to be 1000-1200° C., and the pressure is 100-300 mbar to grow the second high-resistance buffer layer.

Wherein, the thickness of the second high-resistance buffer layer is 100-200 nm. If the thickness of the second high-resistance buffer layer is too thin, it is difficult to effectively fill in the surface differences formed by the treatment layer. If the thickness of the second high-resistance buffer layer is too thick, the process window will be narrowed, and the stability and repeatability are difficult to guarantee. .

The fifth step is to bombard the second high-resistance buffer layer with ion beams.

In the embodiment of the present disclosure, bombarding the second high-resistance buffer layer with an ion beam refers to accelerating and focusing the ion beam generated by the ion source to hit the surface of the second high-resistance buffer layer under vacuum conditions. Among them, the existing ion beam generation method is mainly the accelerator method. The accelerator method is mainly a method of obtaining ions by accelerating particles and colliding different particles to break up atoms. The energy of the ion beam obtained by the ion source from the accelerator generally ranges from hundreds of electron volts to tens of thousands of electron volts. Because the high-energy ion beam obtained by high-extraction voltage is limited by the breakdown, it is necessary to accelerate the ions in the electric field and magnetic field. This type of device is called an accelerator. Various accelerators can be used to obtain high energy (such as hundreds of GeV) for ions, and can also decelerate ions to obtain low energy (such as tens of electron volts) but high-intensity ion beams.

Optionally, the fifth step includes:

Using the ion source mixed with C and Ar, under the vacuum condition of 10 ^-7 ~ 10 ^-5 Pa, the ion beam current generated by the ion source is controlled to be 20 ~ 150mA, the energy is 5 ~ 30KeV, and the power is 5 ~ 20kw. The beam is accelerated and focused so that the ion beam bombards the second high-resistance buffer layer.

Step 6, growing a third high-resistance buffer layer on the second high-resistance buffer layer.

Optionally, the sixth step includes:

The temperature of the reaction chamber is controlled to be 1000-1200° C. and the pressure is 100-300 mbar to grow the third high-resistance buffer layer.

Step 205 , growing a channel layer on the high resistance buffer layer.

Exemplarily, under the conditions of N ₂ and H ₂ atmosphere, the temperature is 900°C-1100°C, and the reaction chamber pressure is 100mbar-200mbar, TMGa is introduced as the group III source, NH ₃ is used as the group V source, and the growth thickness is 15 ~100nm GaN channel layer.

Step 206 , growing an AlGaN barrier layer on the channel layer.

Exemplarily, under the conditions of a pure _H2 atmosphere, a temperature of 950°C to 1200°C, and a reaction chamber pressure of 100mbar to 200mbar, TMGa and TMAl are introduced as Group III sources, _NH3 is used as Group V sources, and the growth thickness is 5 ~20nm AlGaN barrier layer.

Wherein, the molar doping amount of Al in the AlGaN barrier layer is 0.25-0.35.

In the embodiments of the present disclosure, a nucleation layer is first formed on the substrate before the GaN channel layer is grown on the substrate. A porous structure is formed on the core layer, and the relaxation formed by porous GaN can effectively release the piezoelectric stress formed by the AlGaN high-resistance buffer layer and improve the crystal quality of the bottom layer, which is conducive to obtaining a channel layer with higher mobility and two-dimensional electrons. air interface. At the same time, after the growth of the nuclear layer is completed, in the process of growing the high-resistance buffer layer, the high-resistance buffer layer is subjected to a second high-temperature corrosion treatment, so that pores can be further formed on the high-resistance buffer layer. The air in between is non-conductive and can form a high-resistance film to increase impedance and reduce the influence of background carriers on the channel. Then, ion beam bombardment treatment is performed on the high-resistance buffer layer, which is conducive to the formation of uniform dangling bonds on the surface, and maintains the uniformity and consistency of the chemical bonding state, so that the stress extending and accumulating in the epitaxial layer is generally reduced, and the defects are reduced. The crystal quality of the layer is improved, and the electron mobility of the high electron mobility transistor is higher.

3 is a schematic structural diagram of a gallium nitride-based high electron mobility transistor epitaxial wafer provided by an embodiment of the present disclosure. As shown in FIG. 3 , the gallium nitride-based high electron mobility transistor epitaxial wafer includes a substrate 1 and a stacked Nucleation layer 2 , high resistance buffer layer 3 , channel layer 4 and AlGaN barrier layer 5 on substrate 1 .

Optionally, the nucleation layer 2 is a GaN layer with a thickness of 80-150 nm.

Optionally, the high-resistance buffer layer 3 is an AlGaN layer with a thickness of 1-3 um. The high-resistance buffer layer 3 can realize the beneficial effect of dislocation filtering and improve the crystal quality of the epitaxial wafer.

Optionally, the channel layer 4 is a GaN layer with a thickness of 50-300 nm.

The channel layer 4 is a transport channel for the two-dimensional electron gas, and requires flat surface and low doping concentration to reduce the scattering of the two-dimensional electron gas.

Optionally, the thickness of the AlGaN barrier layer 5 is 30-100 nm.

The AlGaN barrier layer 5 will generate a large amount of positive polarized charges at the interface between the barrier layer 5 and the channel layer 4 through its own large white hair polarization or piezoelectric polarization, and the polarized positive charges can be Electrons are attracted to form a two-dimensional electron gas.

In the embodiments of the present disclosure, a nucleation layer is first formed on the substrate before the GaN channel layer is grown on the substrate. A porous structure is formed on the core layer, and the relaxation formed by porous GaN can effectively release the piezoelectric stress formed by the AlGaN high-resistance buffer layer and improve the crystal quality of the bottom layer, which is conducive to obtaining a channel layer with higher mobility and two-dimensional electrons. air interface. At the same time, after the growth of the nuclear layer is completed, in the process of growing the high-resistance buffer layer, the high-resistance buffer layer is subjected to a second high-temperature corrosion treatment, so that pores can be further formed on the high-resistance buffer layer. The air in between is non-conductive and can form a high-resistance film to increase impedance and reduce the influence of background carriers on the channel. Then, ion beam bombardment treatment is performed on the high-resistance buffer layer, which is conducive to the formation of uniform dangling bonds on the surface, and maintains the uniformity and consistency of the chemical bonding state, so that the stress extending and accumulating in the epitaxial layer is generally reduced, and the defects are reduced. The crystal quality of the layer is improved, and the electron mobility of the high electron mobility transistor is higher.

The above is not intended to limit the present disclosure in any form. Although the present disclosure has been disclosed above through the embodiments, it is not used to limit the present disclosure. 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 based on the technical essence of the present disclosure, Equivalent changes and modifications still fall within the scope of the technical solutions of the present disclosure.

Claims (10)

1. A preparation method of gallium nitride-based high electron mobility transistor epitaxial wafer, characterized in that, the preparation method comprises: providing a substrate; growing a nucleation layer on the substrate, and performing a first high-temperature corrosion treatment on the nucleation layer during the process of growing the nucleation layer; A high-resistance buffer layer is grown on the nucleation layer, and during the process of growing the high-resistance buffer layer, the high-resistance buffer layer is sequentially subjected to a second high-temperature corrosion treatment and ion beam bombardment treatment, and the high-resistance buffer layer is The buffer layer is an AlGaN layer; A channel layer and an AlGaN barrier layer are grown sequentially on the high-resistance buffer layer. 2. The preparation method according to claim 1, characterized in that, in the process of growing the nucleation layer, the first high-temperature corrosion treatment is carried out to the nucleation layer, comprising: growing the first nucleation layer; Soaking the first nucleation layer in hot alkali solution for a first set time; Spinning and drying the first nucleation layer after soaking with deionized water; A second nucleation layer is grown on the first nucleation layer. 3. The preparation method according to claim 2, wherein said growing said first nucleation layer comprises: Control the temperature of the reaction chamber to be 600-950°C and the pressure to be 100-300mbar to grow the first nucleation layer, the thickness of the first nucleation layer being 1/3-1/2 of the total thickness of the nucleation layer . 4. preparation method according to claim 2, is characterized in that, described first nucleation layer is immersed in hot alkali NaOH solution for the first set time, comprising: Soaking the first nucleation layer in a hot alkali solution with a KOH or NaOH concentration of 20% to 50% and a temperature of 30 to 60°C for 15 to 35 minutes. 5. The preparation method according to claim 2, wherein said soaking said first nucleation layer is dried with deionized water, comprising: Put the soaked first nucleation layer into an oven, and dry it for 20-60min at 50-150°C and vacuum degree of -500--720pa. 6. The preparation method according to any one of claims 1 to 5, characterized in that, in the process of growing the high-resistance buffer layer, the high-resistance buffer layer is sequentially subjected to a second high-temperature corrosion treatment and ion beam bombardment treatments, including: growing a first high resistance buffer layer; Soaking the first high-resistance buffer layer in hot alkali solution for a second set time; Spinning and drying the first high-resistance buffer layer after soaking with deionized water; growing a second high resistance buffer layer on the first high resistance buffer layer; performing ion beam bombardment on the second high-resistance buffer layer; growing a third high resistance buffer layer on the second high resistance buffer layer. 7. The preparation method according to claim 6, wherein said growing the first high-resistance buffer layer comprises: controlling the temperature of the reaction chamber to be 1000-1200° C., and the pressure to be 100-300 mbar to grow the first high-resistance buffer layer, and the thickness of the first high-resistance buffer layer is 1/2 to 1/2 of the total thickness of the high-resistance buffer layer. 2/3. 8. The preparation method according to claim 6, wherein said soaking said first high-resistance buffer layer in hot alkali solution for a second set time includes: Soak the first high-resistance buffer layer in a hot alkali solution with a concentration of KOH or NaOH of 20%-50% and a temperature of 30-60° C. for 15-35 minutes. 9. The preparation method according to claim 6, wherein the growing the second high-resistance buffer layer on the first high-resistance buffer layer comprises: The temperature of the reaction chamber is controlled to be 1000-1200° C. and the pressure is 100-300 mbar to grow the second high-resistance buffer layer, and the thickness of the second high-resistance buffer layer is 100-200 nm. 10. The preparation method according to claim 6, wherein the ion beam bombardment of the second high-resistance buffer layer comprises: Using the ion source mixed with C and Ar, under the vacuum condition of 10 ^-7 ~ 10 ^-5 Pa, the ion beam current generated by the ion source is controlled to be 20 ~ 150mA, the energy is 5 ~ 30KeV, and the power is 5 ~ 20kw, accelerating and focusing the ion beam so that the ion beam bombards the second high-resistance buffer layer.

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