A method for atmospheric pressure MOCVD epitaxial growth of alpha-Ga2O3 thin film based on t-butyl alcohol precursor

Abstract

The application discloses a method for epitaxially growing an alpha-Ga2O3 film based on a tert-butyl alcohol precursor under normal pressure by MOCVD, and comprises the following steps: cleaning a substrate, placing the cleaned substrate on a reaction chamber base of a metal organic chemical vapor deposition (MOCVD) device, introducing nitrogen into the reaction chamber, adjusting the air pressure of the reaction chamber to normal pressure, performing high-temperature pretreatment on the substrate in the reaction chamber, wherein the high-temperature pretreatment is performed at 1000-1200 DEG C for 15-30 min, cooling the substrate to 570-630 DEG C, taking triethyl gallium as a gallium source precursor and taking tert-butyl alcohol as an oxygen source precursor, and growing an alpha-Ga2O3 film sample on the substrate, and cooling the alpha-Ga2O3 film sample to room temperature while introducing nitrogen to obtain an alpha-Ga2O3 film. The method can be used to prepare a high-quality, high-speed-grown pure-phase metastable alpha-Ga2O3 film.

Description

Technical Field

[0001] This invention relates to the field of microelectronic nanomaterials technology, specifically to a method for atmospheric pressure MOCVD epitaxial growth of α-Ga2O3 thin films based on tert-butanol precursor. Background Technology

[0002] Gallium oxide (Ga₂O₃) is a wide-bandgap semiconductor material with excellent electrical and optical properties. Among its various crystal structures, β-Ga₂O₃ is the most common, with a bandgap of approximately 4.9 eV, a characteristic that makes it promising for applications in optoelectronic devices. Gallium oxide can effectively absorb and emit ultraviolet light, thus it is widely used in the manufacture of high-efficiency photodetectors, ultraviolet light-emitting diodes, and solar cells. Furthermore, gallium oxide possesses good electrical conductivity and thermal stability, and has traditionally been used as an insulating layer in Ga-based semiconductor materials and as an ultraviolet filter. These excellent properties make gallium oxide play a crucial role in modern electronics and optoelectronics, providing new possibilities for the development of high-power and high-frequency electronic devices.

[0003] Alpha-phase gallium oxide (α-Ga₂O₃) is a metastable crystal structure with unique crystallographic features and physical properties. Its wide bandgap, typically around 5.1 eV, makes it a potential candidate for applications in optoelectronic devices, particularly in photodetectors requiring high stability and efficiency. Using inexpensive sapphire substrates (α-Al₂O₃), it is hoped that power and optoelectronic devices combining low cost and high performance can be fabricated on a large scale. However, several technical challenges remain in fabricating high-quality α-phase gallium oxide thin films, such as crystal defects and surface roughness. Solving these problems is crucial for its practical application in devices.

[0004] Currently, gallium oxide thin films are mainly prepared using metal-organic chemical vapor deposition (MOCVD) technology, with oxygen being the most commonly used oxygen source. However, the high reactivity of oxygen can lead to complex and violent parasitic reactions, increasing the risk of carbon contamination and thus affecting the electrical and optical properties of the thin film. In addition, oxygen growth conditions require high thermal stability of the substrate, limiting its application on certain low-temperature substrates.

[0005] Metal-organic chemical vapor deposition (MOCVD) is a widely used technique for growing semiconductor thin films, which deposits films through chemical reactions on the substrate surface. In the preparation of gallium oxide (GaO) films, MOCVD technology can provide precise control over chemical composition and thickness, thereby growing high-quality α-Ga2O3 films. However, traditional MOCVD methods for growing GaO films often suffer from problems such as low epitaxial growth rates and the presence of impurity phases in the films. Therefore, developing new MOCVD processes to solve these problems and achieve rapid epitaxial growth of α-Ga2O3 films is of great significance for the development of microelectronic devices.

[0006] The preparation of high-quality α-Ga₂O₃ thin films has always been a research challenge. Traditional growth methods, such as molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), while capable of producing high-quality films, suffer from low growth rates, high costs, and difficulties in large-scale production. For example, while the Ga₂O₃ films grown by Richgag Industry using MBE technology exhibit low defect density and high electron mobility, the production process is complex and costly. Therefore, developing a new method for efficiently growing high-quality gallium oxide thin films under ambient pressure is of great significance for promoting the practical application of this material. This new method could not only reduce production costs and increase growth rates but also enable large-scale production to meet the growing market demand. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for atmospheric pressure MOCVD epitaxial growth of α-Ga₂O₃ thin films based on tert-butanol precursors. Using this method, low-roughness, high-speed growth of pure-phase metastable α-Ga₂O₃ thin films can be prepared.

[0008] To achieve the above objectives, the technical solution designed by the present invention is as follows:

[0009] This invention provides a method for atmospheric pressure MOCVD epitaxial growth of α-Ga2O3 thin films based on tert-butanol precursor, comprising the following steps:

[0010] (1) Clean the substrate and place the cleaned substrate on the reaction chamber base of the metal-organic chemical vapor deposition equipment;

[0011] (2) Introduce nitrogen into the reaction chamber and adjust the gas pressure in the reaction chamber to 700~760 Torr;

[0012] (3) The substrate in the reaction chamber is subjected to high-temperature pretreatment. The conditions for high-temperature pretreatment are 1000~1200℃ for 15~30min;

[0013] (4) Cool the substrate to 570~630℃, use triethylgallium as gallium source precursor and tert-butanol as oxygen source precursor, and grow α-Ga2O3 thin film sample on the substrate.

[0014] (5) Cool the α-Ga2O3 thin film sample to room temperature and simultaneously introduce nitrogen gas to obtain the α-Ga2O3 thin film.

[0015] Furthermore, the substrate is an M-oriented (10-10) sapphire substrate.

[0016] Furthermore, in step (1), the method for cleaning the substrate includes the following steps:

[0017] S1: Place the substrate in ultrapure deionized water and perform ultrasonic cleaning;

[0018] S2: Pour out the ultrapure deionized water, add acetone, and perform ultrasonic cleaning;

[0019] S3: Pour out the acetone, add anhydrous ethanol, and perform ultrasonic cleaning;

[0020] S4: Pour out the anhydrous ethanol, add ultrapure deionized water and perform ultrasonic cleaning;

[0021] S5: Pour out the ultrapure deionized water, remove the substrate and purge it with nitrogen until dry.

[0022] Furthermore, the ultrasonic cleaning time is 6-10 minutes.

[0023] Furthermore, in step (2), a vacuum pump is used to adjust the gas pressure in the reaction chamber to 760 Torr.

[0024] Furthermore, in step (3), the conditions for the high-temperature pretreatment are 1000℃ for 30 min.

[0025] Furthermore, in step (4), the substrate is cooled to 600°C;

[0026] The specific process for growing α-Ga2O3 thin film samples is as follows: after introducing tert-butanol and triethylgallium for 20-40 min, the introduction of triethylgallium is stopped, and the reaction chamber is purged in a tert-butanol atmosphere for 5-10 min to complete the growth.

[0027] Furthermore, the flow rate of triethylgallium is 120~180 sccm, and the flow rate of tert-butanol is 900~1100 sccm.

[0028] Furthermore, the flow rate of triethylgallium is 150 sccm, and the flow rate of tert-butanol is 1000 sccm.

[0029] The present invention also provides an α-Ga2O3 thin film prepared by the method, wherein the root mean square value of the surface roughness of the α-Ga2O3 thin film is 6.388~19.774 nm.

[0030] The principle of this invention:

[0031] In metal-organic chemical vapor deposition (MOCVD), selecting a suitable oxygen source is one of the key factors for achieving high-quality oxide film growth. Tert-butyl alcohol (t-BuOH), as an organic oxygen source, has significant advantages over traditional oxygen (O2).

[0032] 1. The use of tert-butanol helps improve the uniformity of grown films. In MOCVD, gas transport and reaction kinetics have a significant impact on film uniformity. Tert-butanol molecules have a large diffusion coefficient in the gas phase, allowing for better mixing with the metal-organic precursor and uniform distribution throughout the reaction region. This uniform mixing helps form a uniform reaction layer on the substrate surface, resulting in films with uniform thickness and composition. In contrast, oxygen, as an inorganic gas, has less ideal diffusion and mixing characteristics than organic oxygen sources, especially in complex reactor structures, which may lead to localized non-uniform reactions and thus affect film uniformity.

[0033] 2. The use of tert-butanol can reduce carbon pollution. During MOCVD, the decomposition of organic precursors generates carbon impurities. If these impurities are not effectively removed, they will be incorporated into the grown film, affecting its electrical and optical properties. However, tert-butanol produces fewer carbon atoms during decomposition, and the carbon atoms in its structure are more easily removed by optimizing growth conditions (such as carrier gas flow rate). Furthermore, the CO2 produced by its decomposition products can effectively reduce carbon pollution. In contrast, oxygen, as an inorganic gas, although it does not contain carbon, has high reactivity and may lead to incomplete decomposition of metal-organic precursors or complex gas-phase reactions, thereby increasing the risk of carbon pollution.

[0034] 3. Experiments revealed that tert-butanol can react with triethylgallium at atmospheric pressure to deposit gallium oxide, and the growth rate of α-Ga2O3 thin films is higher, which can effectively reduce the gas pressure cost in MOCVD systems. This characteristic makes the use of tert-butanol as an oxygen source in industrial production more economical, reducing the demand for low-pressure gas supply and lowering equipment complexity and operating costs.

[0035] 4. The phenomenon that α-Ga₂O₃ films can be grown under normal pressure but not under low pressure is mainly determined by the thermodynamic and kinetic equilibrium of the reaction between tert-butanol and triethylgallium. Atmospheric pressure: Under higher pressure, the thermodynamic and kinetic conditions of the reaction system are more favorable for the decomposition and reaction of tert-butanol. Higher pressure can promote the diffusion and mixing of reactant molecules, increasing the reaction rate. Low pressure: Under low pressure, the thermodynamic and kinetic conditions of the reaction system are unfavorable for the decomposition and reaction of tert-butanol. Lower pressure leads to insufficient diffusion and mixing of reactant molecules, thus affecting the reaction rate and crystal quality. In the MOCVD process, tert-butanol serves as the oxygen source, and triethylgallium serves as the gallium source. The overall reaction equation for the formation of gallium oxide (Ga₂O₃) is as follows: 2Ga(C₂H₅)₃ + 3t-BuOH → Ga₂O₃ + 6C₂H₆ + 3H₂O; Triethylgallium decomposes at high temperature, releasing gallium atoms, and tert-butanol decomposes at high temperature, providing oxygen atoms. Gallium oxide is the target product, while water and ethane escape as byproducts. The spontaneity of a chemical reaction can be determined by the change in Gibbs free energy (ΔG). Under normal pressure, the ΔG of this reaction... 0 indicates that the reaction is highly spontaneous.

[0036] The beneficial effects of this invention are:

[0037] 1. The method for preparing α-Ga₂O₃ thin films based on metal-organic chemical vapor deposition (MOCVD) provided by this invention significantly improves the growth rate of α-Ga₂O₃ thin films by precisely controlling the transport process of TEGa and t-BuOH, their molar ratio during epitaxial growth, and key processing steps such as high-temperature pretreatment of the substrate. This method uses t-BuOH as a novel precursor, opening up new possibilities for the preparation of α-Ga₂O₃ thin films and overcoming the limitations of traditional oxygen sources. Simultaneously, this method achieves atmospheric pressure growth of α-Ga₂O₃ thin films, effectively avoiding the complex gas management and equipment requirements that may be introduced during low-pressure growth, reducing the performance requirements of growth equipment, and simplifying the process flow. This technological breakthrough not only enriches the industry's ideas on thin film epitaxy but also provides strong support for the large-scale production of α-Ga₂O₃ thin films, helping to significantly improve production efficiency, reduce production costs, and promote the widespread application of α-Ga₂O₃ thin films in optoelectronics, power electronics, and other fields, possessing significant economic and social value.

[0038] 2. In this invention, a high-temperature pretreatment of the substrate is performed before the epitaxial growth of the α-Ga2O3 thin film material. This step is a key step, and its main objectives include the following aspects:

[0039] (1) Remove surface impurities: Through high-temperature pretreatment, organic and inorganic pollutants on the surface are decomposed and volatilized, and surface impurities are oxidized and removed, thereby providing a clean surface that is beneficial for subsequent epitaxial growth.

[0040] (2) Activating substrate surface atoms: High temperature pretreatment can activate the atoms on the substrate surface, improve their chemical activity, and make them more likely to react with the precursor of the epitaxial layer, thereby forming a uniform epitaxial layer, while improving the growth rate and quality of the epitaxial layer.

[0041] (3) Reduce thermal stress: High temperature pretreatment can make the substrate and epitaxial layer have closer thermal expansion coefficients during growth, thereby reducing the generation of thermal stress and improving the stability of the epitaxial layer.

[0042] 3. By adjusting the carrier gas flow rate and preset gas pressure, this invention optimizes the thin film growth environment, which helps to obtain more uniform thin films. Better crystal quality and fewer defects are crucial for improving the performance of microelectronic devices.

[0043] 4. This invention uses tert-butanol (t-BuOH) as the oxygen source precursor for thin film growth. The use of tert-butanol offers advantages in terms of economy and ease of operation. Compared to oxygen, tert-butanol is a common organic solvent with relatively low price and is readily available and stored in both laboratory and industrial production. Furthermore, using tert-butanol as an oxygen source simplifies reaction condition control, eliminating the need for complex gas handling systems and reducing equipment and operational complexity. This makes tert-butanol an ideal oxygen source choice in MOCVD technology, particularly in applications requiring high-quality oxide thin films. Attached Figure Description

[0044] Figure 1 This is a flowchart of a method for atmospheric pressure MOCVD epitaxial growth of α-Ga2O3 thin films based on tert-butanol precursor;

[0045] Figure 2 The time spectrum of α-Ga2O3 thin film grown under ambient pressure using tert-butanol as oxygen source precursor, provided in Example 1, is based on an in-situ laser reflection monitoring system.

[0046] Figure 3 The time spectrum of α-Ga2O3 thin film grown under low pressure using O2 as oxygen source precursor is based on an in-situ laser reflection monitoring system.

[0047] Figure 4 AFM image of α-Ga2O3 thin film grown on substrate without high-temperature pretreatment;

[0048] Figure 5 AFM image of the α-Ga2O3 thin film grown on the substrate provided in Example 1 after high-temperature pretreatment;

[0049] Figure 6 XRD pattern of the α-Ga2O3 thin film provided in Example 1;

[0050] Figure 7 XRC-ω rocking curve of the α-Ga2O3 thin film provided in Example 1. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can understand it.

[0052] Example 1

[0053] A method for atmospheric pressure MOCVD epitaxial growth of α-Ga2O3 thin films based on tert-butanol precursor

[0054] This embodiment provides a method for preparing high-performance, high-quality α-Ga2O3 thin films on sapphire substrates under ambient pressure using an MOCVD (Atmospheric Pressure MOCVD, AP-MOCVD) device. Figure 1 As shown, it includes the following steps:

[0055] 1. Precursors for thin film growth are selected, with tert-butanol (t-BuOH) as the oxygen source and high-purity triethylgallium (TEGa) as the gallium source. All precursors are stored in a water bath with a thermostat to maintain a constant temperature, which facilitates precise control of the precursor flow rate.

[0056] The water bath containing t-BuOH is controlled at a constant temperature of 32℃ by a constant temperature controller, while the water bath containing TEGa is controlled at a constant temperature of 22℃ by a constant temperature controller.

[0057] 2. M-oriented (10-10) sapphire (α-Al2O3) was selected as the substrate for growing α-Ga2O3 thin films. The M-oriented (10-10) sapphire substrate was cleaned, and the cleaned and dried M-oriented (10-10) sapphire substrate was placed on the reaction chamber base of the metal-organic chemical vapor deposition (MOCVD) equipment. The cleaning process is as follows:

[0058] (1) Place the substrate in a beaker, add ultrapure deionized water and ultrasonically clean it for 6-10 min. The resistivity of the ultrapure deionized water is greater than 18.25 MΩ. cm;

[0059] (2) Pour out the ultrapure deionized water, then add acetone and perform ultrasonic cleaning for 6-10 min;

[0060] (3) Pour out the acetone, then add anhydrous ethanol and perform ultrasonic cleaning for 6-10 min;

[0061] (4) Pour out the anhydrous ethanol, then add ultrapure deionized water and perform ultrasonic cleaning for 6-10 min;

[0062] (5) Pour out the ultrapure deionized water, then remove the substrate and purge it with nitrogen until dry to ensure that the substrate is clean and free of residual moisture.

[0063] 3. Start the MOCVD equipment and introduce nitrogen (N2) into the passage (the nitrogen should be introduced until the end of the experiment). After the air in the reaction chamber is exhausted, use a vacuum pump to adjust the gas pressure in the reaction chamber to 760 Torr, which is the atmospheric pressure level, in order to remove the air from the reaction chamber.

[0064] 4. Activate the heating wire to heat the substrate tray in the reaction chamber, and perform high-temperature pretreatment on the M-oriented (10-10) sapphire substrate in an N2 atmosphere at a temperature of 1000~1200℃ for 15~30 min. Activate the in-situ laser reflectometer monitoring system to monitor the growth process in real time.

[0065] 5. Subsequently, the substrate was cooled to a suitable temperature of 570~630℃ for epitaxial growth of α-Ga2O3 thin films. High-purity triethylgallium (TEGa) was used as the gallium source precursor and t-BuOH as the oxygen source precursor. α-Ga2O3 thin films were grown on M-oriented (10-10) sapphire substrates using AP-MOCVD technology for 20~40 min. The TEGa supply was stopped, and the temperature was kept constant. The reaction chamber was purged in a t-BuOH atmosphere for 5~10 min, and the growth was completed.

[0066] The experimental parameters are as follows: the flow rate of the group III source (TEGa) is 120–180 sccm, and the flow rate of the group VI source (t-BuOH) is 900–1100 sccm. Under these parameters, the flow rate ratio (molar ratio) of group VI source to group III source (VI / III) is 81.48, the monitoring laser wavelength of the in-situ laser reflectometer monitoring system is 163.2 nm, and the carrier gas flow rate of nitrogen is 7000 sccm.

[0067] 6. Turn off the MO source and initiate the cooling process, continuously purging the pipeline with N2 to prevent blockage. Once the reaction chamber temperature has dropped to room temperature, remove the α-Ga2O3 thin film sample from the MOCVD equipment to obtain an α-Ga2O3 thin film grown by atmospheric pressure MOCVD based on a tert-butanol precursor. The time spectrum of the α-Ga2O3 thin film obtained in this example using the in-situ laser reflection monitoring system is shown below. Figure 2 As shown.

[0068] Example 2

[0069] A method for atmospheric pressure MOCVD epitaxial growth of α-Ga2O3 thin films based on tert-butanol precursor

[0070] This embodiment provides a method for preparing high-performance, high-quality α-Ga2O3 thin films on sapphire substrates under ambient pressure using an MOCVD device. The method is the same as in Embodiment 1, except that:

[0071] 1. In step 4, the high-temperature pretreatment conditions are 1000℃ for 30 min;

[0072] 2. In step 5, the suitable temperature for epitaxial growth of α-Ga2O3 thin film is 600℃, the flow rate of triethylgallium is 150 sccm, and the flow rate of tert-butanol is 1000 sccm.

[0073] Example 3

[0074] Performance Study of α-Ga2O3 Thin Films Grown by Atmospheric Pressure MOCVD Based on Tert-Butanol Precursor

[0075] 1. The growth process of the α-Ga2O3 thin film in Example 1 was monitored using an in-situ laser reflectometer monitoring system to study the growth rate and film thickness. Three control groups were also set up:

[0076] Control group 1 used tert-butanol as the oxygen source to grow α-Ga2O3 thin films by low-pressure MOCVD;

[0077] Control group 2 used oxygen as the oxygen source and grew α-Ga2O3 thin films by MOCVD at ambient pressure;

[0078] Control group 3 used oxygen as the oxygen source to grow α-Ga2O3 thin films using low-pressure MOCVD. The time spectrum of its in-situ laser reflection monitoring system is shown below. Figure 3 As shown.

[0079] According to the in-situ laser reflectometer monitoring system, no α-Ga2O3 film was found to grow in control group 1 and control group 2. The results of control group 1 show that α-Ga2O3 film cannot be prepared under low pressure when tert-butanol is used as the oxygen source. The results of control group 2 show that α-Ga2O3 film cannot be prepared under normal pressure when oxygen is used as the oxygen source.

[0080] Combination Figure 2 and Figure 3 As shown, the film thickness corresponding to a single oscillation cycle is 164.8 nm. The growth rate under ambient pressure growth conditions based on tert-butanol as the oxygen source is 576.8 nm / h, which is significantly higher than the growth rate (428 nm / h) when using O2 as the oxygen source under low pressure conditions.

[0081] 2. The surface morphology of the α-Ga2O3 film prepared in Example 1 was studied using atomic force microscopy (AFM). Meanwhile, the α-Ga2O3 film prepared using the method of Example 1 but without the high-temperature pretreatment step (i.e., step 4 in Example 1) was used as a control.

[0082] Combination Figure 4 and Figure 5 As shown, the AFM scan range is 2. 2 μm 2 The surface of the α-Ga2O3 epitaxial film after high-temperature pretreatment is smoother, and its surface roughness is significantly lower than that of the α-Ga2O3 epitaxial film without high-temperature pretreatment. The root mean square (RMS) value of the surface roughness of the α-Ga2O3 epitaxial film without high-temperature pretreatment is 47.655 nm, while the RMS value of the α-Ga2O3 epitaxial film after high-temperature pretreatment (i.e., the α-Ga2O3 film of Example 1) is 11.799 nm, demonstrating that high-temperature pretreatment significantly improves the quality of the epitaxial film.

[0083] 3. The crystal quality of the α-Ga₂O₃ thin film in Example 1 was characterized using X-ray diffraction (XRD). For example... Figure 6 As shown, a single and strong (30-30) crystal plane diffraction peak was observed at a diffraction angle (2θ) of 64.76°, indicating that the α-Ga2O3 film has good crystal orientation, thus proving the effectiveness of the growth process.

[0084] 4. The crystal quality of the α-Ga₂O₃ thin film in Example 1 was characterized using the ω-rocking curve technique in X-ray diffraction (XRD). For example... Figure 7 As shown, the (10-10) diffraction peak of the α-Ga2O3 thin film in Example 1 exhibits high intensity and a narrow full width at half maximum (FWHM), with an FWHM value of 0.567°. The low FWHM value indicates good crystal orientation and fewer lattice distortions and defects, thus demonstrating that the α-Ga2O3 thin film of the present invention has good crystal quality.

[0085] All other parts not described in detail are existing technologies. Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for atmospheric pressure MOCVD epitaxial growth of α-Ga2O3 thin films based on tert-butanol precursor, characterized in that: Includes the following steps: (1) Clean the substrate and place the cleaned substrate on the reaction chamber base of the metal-organic chemical vapor deposition equipment; (2) Introduce nitrogen into the reaction chamber and adjust the gas pressure in the reaction chamber to 700~760 Torr; (3) The substrate in the reaction chamber is subjected to high-temperature pretreatment. The conditions for high-temperature pretreatment are 1000~1200℃ for 15~30min; (4) Cool the substrate to 600℃, and grow α-gallium on the substrate using triethylgallium as the gallium source precursor and tert-butanol as the oxygen source precursor. Ga2O3 thin film sample; (5) For α The Ga2O3 thin film sample was cooled to room temperature while nitrogen gas was introduced to obtain α Ga2O3 thin film; In step (4), α is grown The specific process for the Ga2O3 thin film sample is as follows: after introducing tert-butanol and triethylgallium for 20-40 min, the introduction of triethylgallium is stopped, and the reaction chamber is purged in a tert-butanol atmosphere for 5-10 min to complete the growth. The flow rate of triethylgallium is 120~180 sccm, and the flow rate of tert-butanol is 900~1100 sccm.

2. The method according to claim 1, characterized in that: The substrate is an M-oriented (10-10) sapphire substrate.

3. The method according to claim 1, characterized in that: In step (1), the method for cleaning the substrate includes the following steps: S1: Place the substrate in ultrapure deionized water and perform ultrasonic cleaning; S2: Pour out the ultrapure deionized water, add acetone, and perform ultrasonic cleaning; S3: Pour out the acetone, add anhydrous ethanol, and perform ultrasonic cleaning; S4: Pour out the anhydrous ethanol, add ultrapure deionized water and perform ultrasonic cleaning; S5: Pour out the ultrapure deionized water, remove the substrate and purge it with nitrogen until dry.

4. The method according to claim 3, characterized in that: The ultrasonic cleaning time is 6-10 minutes.

5. The method according to claim 1, characterized in that: In step (2), a vacuum pump is used to adjust the gas pressure in the reaction chamber to 760 Torr.

6. The method according to claim 1, characterized in that: In step (3), the conditions for the high-temperature pretreatment are 1000℃ for 30 min.

7. The method according to claim 1, characterized in that: The flow rate of triethylgallium is 150 sccm, and the flow rate of tert-butanol is 1000 sccm.

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