Room temperature printed GaN semiconductor thin film and preparation method and application thereof

Abstract

This invention provides a room-temperature-printable GaN semiconductor thin film, its preparation method, and its applications. The GaN thin film of this invention comprises: a substrate; and a GaN thin film layer, wherein a Ga-based liquid metal coating on the surface of the substrate is printed by a scraping process. This invention also provides a method for preparing the room-temperature-printable GaN thin film. The room-temperature-printable GaN thin film of this invention achieves room-temperature printing preparation of two-dimensional GaN semiconductor thin films, solving the problems of high cost, low efficiency, and complex processes faced by vapor phase epitaxy in the preparation of GaN thin films, and is conducive to promoting the large-scale application of GaN thin films in the field of power semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a room-temperature printed GaN semiconductor thin film, its preparation method, and its application. Background Technology

[0002] Compared to first-generation Si-based semiconductors, third-generation GaN semiconductors offer significant advantages in bandgap, electron mobility, critical breakdown electric field strength, thermal conductivity, and Baliga figure of merit. GaN semiconductor power devices offer advantages such as high precision, high power density, low power consumption, and radiation resistance, making them a viable alternative to Si-based semiconductor power devices and meeting the stringent requirements of next-generation power electronic systems for semiconductor power devices in terms of high temperature, high frequency, and high power.

[0003] Currently, the key to the large-scale application of GaN in semiconductor power devices lies in how to efficiently and cost-effectively prepare high-quality GaN thin films. At present, GaN thin films are mainly obtained by deposition and growth on sapphire or Si substrates using methods such as metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). While these methods can grow high-quality single-crystal GaN thin films, the growth rate is slow. The complex processes, high equipment maintenance costs, and slow film growth rate make the cost of GaN thin films prepared by these methods very high, which is clearly detrimental to the large-scale industrial production of GaN power devices. Therefore, the convenient, efficient, and cost-effective preparation of high-quality GaN thin films and the construction of GaN semiconductor devices are crucial for the application of GaN in high-temperature, high-frequency, and radiation-resistant high-power semiconductor devices. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a room-temperature printable GaN semiconductor thin film, its preparation method, and its applications. The preparation method of this invention utilizes low-temperature plasma technology to ionize N2 or NH3 molecules at room temperature, thereby achieving a reaction between N2 or NH3 and Ga on a Ga-based liquid metal surface. This allows for the direct growth of GaN thin films onto the Ga-based liquid metal surface at room temperature. Furthermore, the GaN thin film on the Ga-based liquid metal surface is transferred to an electronic device substrate using a printing method, achieving large-area printing deposition of high-quality GaN thin films on the substrate surface.

[0005] Specifically, the present invention provides the following technical solution:

[0006] A GaN thin film, comprising:

[0007] Substrate;

[0008] The GaN thin film layer is printed onto the surface of the substrate by scraping a Ga-based liquid metal coating on the GaN thin film.

[0009] According to an embodiment of the present invention, the substrate is selected from at least one of SiO2 / Si wafers, quartz wafers, sapphire wafers, Si wafers, or flexible plastic films. Preferably, the flexible plastic film is made of at least one of polyimide (PI), polyetheretherketone (PEEK), polyvinyl chloride (PVT), polydimethylsiloxane (PDMS), or polyethylene terephthalate (PET).

[0010] According to an embodiment of the present invention, the surface of the substrate is preferably treated with low-temperature plasma. Low-temperature plasma treatment can increase the affinity of the substrate surface, which is beneficial for the printing and deposition of GaN thin films on the substrate surface to obtain GaN thin film layers.

[0011] According to an embodiment of the present invention, the thickness of the substrate is 50 to 500 μm.

[0012] According to an embodiment of the present invention, the surface roughness Ra of the substrate is ≤0.2μm.

[0013] According to an embodiment of the present invention, the thickness of the GaN thin film layer is 1.4 to 50 nm.

[0014] According to an embodiment of the present invention, the bandgap of the GaN thin film layer is 3.4 to 3.6 eV.

[0015] According to an exemplary embodiment of the present invention, when the thickness of the GaN thin film layer is 0.5 to 2 nm, the band gap of the GaN semiconductor thin film is 3.4 to 3.6 eV, preferably 3.4 to 3.5 eV.

[0016] According to an exemplary embodiment of the present invention, when the thickness of the GaN thin film layer is 4 to 20 nm, the band gap of the GaN semiconductor thin film is 3.4 to 3.6 eV.

[0017] According to an embodiment of the present invention, the melting point of the Ga-based liquid metal is, for example, below 40°C, preferably 0–30°C.

[0018] According to an embodiment of the present invention, the Ga-based liquid metal is selected from Ga, and at least one of the following metals: In, Sn or Bi.

[0019] Preferably, by mass percentage, the Ga-based liquid metal comprises: 20.5-30% metallic In, 0-12.5% ​​metallic Sn, 0-5% metallic Bi, and the balance being metallic Ga.

[0020] According to an embodiment of the present invention, in the Ga-based liquid metal with a GaN thin film covering the surface, the GaN thin film has a two-dimensional structure. Preferably, the thickness of the GaN thin film is 0.5–1.6 nm, for example, 1.4–1.6 nm.

[0021] The present invention also provides a method for preparing the above-mentioned GaN thin film, comprising:

[0022] 1) GaN thin films are grown on the surface of Ga-based liquid metal by plasma treatment;

[0023] 2) Transfer the Ga-based liquid metal obtained in step 1) to the surface of the substrate and spread it to cover the surface of the substrate. Then remove the Ga-based liquid metal on the substrate to obtain a GaN thin film layer on the substrate surface.

[0024] Optionally, 3) repeat step 2) to obtain GaN thin film layers of different thicknesses.

[0025] According to embodiments of the present invention, the preparation methods are all carried out in an inert atmosphere.

[0026] Preferably, the inert atmosphere has an oxygen content of less than 10 ppm and a water content of less than 5 ppm. More preferably, the inert atmosphere has an oxygen content of less than 3 ppm and a water content of less than 0.5 ppm.

[0027] Preferably, the inert atmosphere comprises at least a gas mixture containing N2.

[0028] More preferably, the mixed gas comprises, by volume percentage: 0-20% NH3, 0-10% Ar, and the balance being N2.

[0029] According to an embodiment of the present invention, in step 1), the surface of the Ga-based liquid metal is free of oxide film, thereby enabling the growth of GaN thin films on the surface of the Ga-based liquid metal during plasma processing.

[0030] According to an embodiment of the present invention, the Ga-based liquid metal is selected from Ga, and at least one of the following metals: In, Sn or Bi.

[0031] Preferably, by mass percentage, the Ga-based liquid metal comprises: 20.5-30% metallic In, 0-12.5% ​​metallic Sn, 0-5% metallic Bi, and the balance being metallic Ga.

[0032] In this invention, the Ga-based liquid metal can be prepared by methods known in the art, such as heating a mixed metal or alloy containing at least metallic Ga to a molten state, stirring thoroughly, and then cooling to obtain room temperature Ga-based liquid metal.

[0033] According to an embodiment of the present invention, in step 1), the Ga-based liquid metal is subjected to low-temperature plasma treatment, with conditions including, for example: a treatment time of 1–10 min, preferably 3–5 min; a low-temperature plasma excitation voltage of 40–60 kV, preferably 50–55 kV; and a low-temperature plasma excitation electric field strength of 2–12 × 10⁻⁶ kV. 7 V / m, preferably 3.3~5.5×10 7 V / m. For example, the Ga-based liquid metal is subjected to low-ion plasma treatment in a cryogenic plasma analyzer.

[0034] According to an embodiment of the present invention, in step 1), the low-temperature plasma is formed by exciting an N2-containing mixed gas using a high-voltage electric field. Preferably, the N2-containing mixed gas has the meaning described above. In this invention, the oxygen content in the inert atmosphere is strictly controlled to avoid the introduction of oxygen plasma into the plasma.

[0035] According to an embodiment of the present invention, in step 2), a scraper is used to spread the Ga-based liquid metal with the GaN thin film covering the surface onto the surface of the substrate, and then the substrate is left to stand. Preferably, the standing time is 30 seconds to 3 minutes.

[0036] According to an embodiment of the present invention, the scraper is selected from a flexible plastic film. Preferably, the material of the flexible plastic film is selected from at least one of polyimide (PI), polyetheretherketone (PEEK), polyvinyl chloride (PVT), polydimethylsiloxane (PDMS), or polyethylene terephthalate (PET), and is preferably polydimethylsiloxane (PDMS).

[0037] According to an embodiment of the present invention, in step 2), the temperature of the coating is less than 50°C, preferably 20-40°C.

[0038] According to an embodiment of the present invention, in step 2), after removing the Ga-based liquid metal from the substrate, it is preferable to further clean the residual Ga-based liquid metal on the substrate. The cleaning method is not specifically limited in the present invention; any method known in the art can be used, as long as the residual Ga-based liquid metal on the substrate can be thoroughly cleaned, such as by cleaning with cotton soaked in alcohol.

[0039] According to an embodiment of the present invention, in step 2), the surface of the substrate is subjected to low-temperature plasma treatment, preferably performed in an atmospheric environment. Preferably, a plasma known in the art can be used. Low-temperature plasma treatment can increase the affinity of the substrate surface, which is beneficial for the printing and deposition of GaN thin films on the substrate surface to obtain a GaN thin film layer. Exemplarily, the conditions for low-temperature plasma treatment include: a treatment power of 1000-2000W, preferably 1500-1800W; and a treatment time of 10s-2min, preferably 30s-1min.

[0040] According to an embodiment of the present invention, in step 3), repeated scraping is performed on the surface of the substrate, for example, 1-50 times, or for example, scraping 1-30 times.

[0041] The present invention also provides the application of the above-described GaN thin film in semiconductor power devices.

[0042] According to an embodiment of the present invention, the semiconductor power device includes at least one of a thin-film transistor, a PN junction diode, an LED, a frequency multiplier, and a photomultiplier tube.

[0043] The present invention also provides a thin-film transistor comprising the GaN thin film described herein.

[0044] The present invention also provides a PN junction diode, comprising the GaN thin film described in the present invention.

[0045] Beneficial effects:

[0046] The room-temperature printed GaN thin film provided by this invention realizes the printing preparation of two-dimensional GaN semiconductor thin films at room temperature. This invention directly grows GaN thin films on the surface of Ga-based liquid metal and obtains a high-quality GaN thin film layer with controllable thickness on the substrate surface by printing. It solves the problems of high cost, low efficiency and complex process faced by the vapor phase epitaxy method for preparing GaN thin films, which is conducive to promoting the large-scale application of GaN thin films in the field of power semiconductor devices and provides a room-temperature printing preparation method for GaN-based semiconductor devices.

[0047] The room-temperature printing method for preparing GaN thin films provided by this invention features a short process flow, convenient operation, low energy consumption, and strong controllability. The raw materials required for preparing GaN thin films are non-toxic and reusable, resulting in minimal environmental pollution. The preparation method provided by this invention, through rational process design, enables continuous and large-scale efficient production of GaN thin films, ensuring the economic viability of GaN thin films in semiconductor devices. Attached Figure Description

[0048] Figure 1This is a schematic diagram of the process for generating a GaN thin film on a Ga-based liquid metal surface in Example 1, where 1-glove box, 2-negative electrode of high-voltage DC power supply, 3-positive electrode of high-voltage DC power supply, 4-wire, 5-positive electrode stainless steel disk, 6-nitrogen plasma, and 7-room temperature liquid Ga. 67 In 20.5 Sn 12.5 Alloy, 8-negative electrode stainless steel plate, 9-ground wire.

[0049] Figure 2 This is a schematic diagram of printing and depositing a GaN thin film on the substrate surface in Example 1, where A1 represents the Si / SiO2 wafer, A2 represents the GaN film covering the substrate, and A3 represents the substrate. 67 In 20.5 Sn 12.5 Liquid alloy, A3-PDMS scraper, A4-two-dimensional GaN thin film.

[0050] Figure 3 This is a schematic diagram of the thin-film transistor structure constructed by printing GaN thin films at room temperature in Example 1, wherein B1 is the source, B2 is the drain, B3 is the GaN thin film layer, B4 is the SiO2 dielectric layer, B5 is the gate, and B6 is the Si substrate layer.

[0051] Figure 4 This is a diagram showing the electrical output characteristics of the GaN thin-film transistor in Example 1.

[0052] Figure 5 The graph shows the on / off ratio of the GaN thin film transistors in Examples 1 and 2 as a function of the GaN thin film thickness.

[0053] Figure 6 The graph shows the variation of the bandgap width of the GaN semiconductor thin film with the thickness of the GaN thin film in Examples 1 and 2.

[0054] Figure 7 This is a schematic diagram of the PN junction diode structure in Example 3, where C1 is the positive electrode, C2 is the negative electrode, C3 is the N-type semiconductor Si substrate, and C4 is the P-type semiconductor GaN thin film layer.

[0055] Figure 8 The image shows the IV characteristic curve of the PN junction diode in Example 3. Detailed Implementation

[0056] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0057] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0058] Example 1

[0059] A GaN thin film having a GaN thin film layer with a thickness of 4 nm and a thin film transistor constructed from the GaN thin film.

[0060] 1. Preparation of GaN thin films:

[0061] (1) Adjust the atmosphere in the glove box to a mixture of 95% N2 and 5% Ar (by volume percentage), and control the O2 content in the glove box to below 2 ppm and the H2O content to below 0.1 ppm.

[0062] (2) A 2-inch diameter Si / SiO2 wafer (a Si-P16551 single-crystal silicon wafer manufactured by Zhongnuo New Materials (Beijing) Technology Co., Ltd.) with a 0.5 mm thick Si substrate and a 500 nm thick SiO2 dielectric layer was placed on the discharge roller of a low-temperature plasma instrument (an HCS-100~3500S corona treatment station manufactured by Nanjing Suman Plasma Technology Co., Ltd.), with the SiO2 dielectric layer facing the discharge electrode. The low-temperature plasma power was set to 1800W, the processing temperature was room temperature, the processing conditions were atmospheric conditions, the processing time was 1 min, and the surface roughness Ra was 0.15 μm. The treated Si / SiO2 wafer was wrapped in plastic wrap and transferred to a glove box.

[0063] (3) Preparation of Ga 67 In 20.5 Sn 12.5 Room temperature liquid metal: 67g Ga, 20.5g In, and 12.5g Sn were measured using a balance and placed in a clean ceramic crucible. The crucible was then placed on an electromagnetic stirring platform inside a glove box, with the platform temperature set to 250℃. After the metals had completely melted, the electromagnetic stirring was turned on, with the stirring speed set to 400 r / min. After stirring for 5 minutes, the electromagnetic stirring and heating were turned off, and the mixture was allowed to cool naturally to obtain Ga with a melting point of 10.5℃. 67 In 20.5 Sn 12.5 Liquid metal.

[0064] (4) Growth of GaN thin film on Ga-based liquid metal surface: In a glove box, 10 ml of the Ga-based liquid metal prepared in step (2) was drawn using a disposable plastic syringe and placed on the surface of the negative electrode stainless steel plate of the plasma triggering device. The distance between the positive electrode discharge disk and the Ga-based liquid metal surface was adjusted to 1 mm, and the voltage between the positive and negative electrodes of the plasma triggering device was adjusted to 50 kV. At this time, the electric field strength for exciting N2 plasma was 5 × 10⁻⁶.7 V / m. After 5 min of N2 plasma glow discharge treatment, a GaN thin film can be obtained on the Ga-based liquid metal surface, with a thickness controlled at 1.5 ± 0.2 nm. A schematic diagram of the GaN thin film fabrication process is shown below. Figure 1 As shown.

[0065] (5) Printing GaN thin film on the dielectric layer surface: Place the Si / SiO2 wafer treated with low-temperature plasma in step (2) on a temperature-controlled coating platform, with the inside of the dielectric layer plasma facing upwards. Place the Ga-based liquid metal with a GaN thin film surface after N2 plasma treatment in step (4) on the plasma-treated surface of the SiO2 dielectric layer, and use a PDMS scraper to uniformly coat the Ga-based liquid metal onto the surface of the SiO2 dielectric layer in one go. The coating process diagram is shown below. Figure 2 As shown. After standing for 3 minutes, remove the Ga-based liquid metal from the surface of the dielectric layer and clean the dielectric layer with cotton soaked in alcohol until the Ga-based liquid metal is completely removed.

[0066] (6) After repeating steps (4) and (5) three times, a GaN thin film with a thickness of 4 nm is printed and deposited on the surface of the Si / SiO2 wafer to obtain the GaN thin film.

[0067] 2. Fabrication of GaN thin-film transistors:

[0068] (1) The GaN thin film prepared above was tightly covered with a 7 μm thick polyethylene plastic wrap, leaving a 1 cm × 1 cm GaN thin film area uncovered by the plastic wrap at the edge. A 1 mol / L HF solution was dropped onto the uncovered GaN thin film area using a dropper. After etching for 10 s, the HF solution was removed with a cotton ball soaked in alcohol to expose the Si substrate.

[0069] (2) Printing the gate, source, and drain: The Si / SiO2 wafer etched in step (6) was placed on a temperature-controlled coating platform, and then a stainless steel electrode mask was completely covered over the GaN thin film area and the exposed Si substrate area. A commercially available conductive silver paste (SNM8201 low-temperature silver paste produced by Hunan Guoyin New Materials Co., Ltd.) was applied to the electrode mask in one pass using a PDMS scraper. The gate was printed in the exposed Si substrate area, and the source and drain were printed in the GaN thin film area. After removing the mask, the substrate was placed on a heating stage, and the temperature was set to 120°C. After drying the printed gate, source, and drain for 30 minutes, a GaN thin film transistor was obtained. A schematic diagram of the GaN thin film transistor structure is shown below. Figure 3 As shown; the source, drain, and gate dimensions are 0.3mm × 1mm, and the channel width between the source and drain is 50μm.

[0070] Example 2

[0071] 1. Preparation of GaN thin films: Compared with Example 1, the difference is that the thicknesses of the GaN thin film layers printed and deposited on the Si / SiO2 wafer surface are 1.4nm, 10nm and 20nm, respectively; the rest is the same as in Example 1.

[0072] 2. Fabrication of GaN thin film transistors: Transistors with GaN thin films of different thicknesses were prepared according to the method described in Example 1.

[0073] Test Example 1

[0074] 1. On / off ratio test: The electrical characteristics of the GaN thin film transistors prepared in Examples 1-2 were measured using a Keithly-4200 semiconductor parameter analyzer. The parameters of the Keithly-4200 semiconductor parameter analyzer were as follows: the gate cycle voltage was set to -10V to 10V, the cycle step size was 0.05V / s, and the source voltage was set to -1V.

[0075] The on / off ratio of the GaN thin-film transistors in Examples 1 and 2 varies with the GaN thin-film thickness as follows: Figure 5 As shown. From Figure 5 As can be seen, the GaN thin-film transistor with a GaN thin film thickness of 4 nm has the highest on / off ratio, which is 2.06 × 10⁻⁶. 5 When the GaN thin film thickness in the transistor exceeds 4 nm, the on / off ratio of the thin film transistor decreases with increasing GaN thin film thickness.

[0076] The electrical output characteristics of the transistor in Example 1 were tested using the Keithly-4200 semiconductor parameter analyzer described above. Figure 4 As shown. From Figure 4 As can be seen from the data, the GaN thin-film transistor of Example 1 exhibits significant current regulation characteristics. The threshold voltage of the transistor is approximately -0.3V, the subthreshold swing is approximately 98mV, and the on / off ratio is 2.06 × 10⁻⁶. 5 .

[0077] 2. Bandgap Width: The bandgap width of the GaN semiconductor thin films prepared in Examples 1-2 was measured using a Hitachi U3900 UV-vis spectrophotometer. The parameters of the Hitachi U3900 UV-vis spectrophotometer were as follows: absorption spectrum wavelength set to 200 to 800 nm, scan step size of 5 nm / s. The variation of the GaN thin film bandgap width with GaN thin film thickness in Examples 1 and 2 is shown below. Figure 6 As shown. From Figure 6As can be seen, the bandgap of the GaN thin film first decreases and then increases with the thickness of the GaN thin film. When the thickness of the GaN thin film in the transistor is less than 4 nm, the bandgap of the thin film transistor decreases with increasing GaN thin film thickness. For example, the bandgap is 3.42 eV when the GaN thin film thickness is 1.4 nm, and 3.41 eV when the GaN thin film thickness is 4 nm. When the thickness of the GaN thin film in the transistor exceeds 4 nm, the bandgap of the thin film transistor increases with increasing GaN thin film thickness. For example, the bandgap is 3.48 eV and 3.52 eV when the GaN thin film thickness is 10 nm and 20 nm, respectively.

[0078] Example 3

[0079] 1. The method for preparing the GaN thin film differs from that in Example 1 in that: in this example, an N-type semiconductor Si wafer is used as the substrate, and a PN junction diode is constructed using a room-temperature printed P-type semiconductor GaN thin film and an N-type semiconductor Si substrate. A schematic diagram of the PN junction diode is shown below. Figure 7 As shown; the dimensions of the N-type semiconductor Si substrate are the same as in Example 1. Everything else is the same as in Example 1, and a P-type semiconductor GaN thin film is printed on the N-type semiconductor Si substrate.

[0080] 2. Fabrication of PN junction diode: Silver electrodes were printed on the GaN thin film layer and Si surface using the same method as in Example 1, which served as the positive and negative electrodes of the PN junction diode, respectively.

[0081] Test Example 2

[0082] 1. PN Junction Diode IV Characteristic Curve: The IV characteristic curve of the PN junction diode in Example 3 was measured using a Keithly-4200 semiconductor parameter analyzer. The parameters of the Keithly-4200 semiconductor parameter analyzer were as follows: source-drain cycle voltage set to -10V to 10V, cycle step size of 0.05V / s. The IV characteristic curve of the PN junction diode is shown below. Figure 8 As shown. From Figure 8 As can be seen, the PN junction diode employing the GaN thin film layer of this invention exhibits typical rectification characteristics, with a rectification ratio of approximately 1.5 × 10⁻⁶ at voltages of 10V and -10V. 3 .

[0083] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A GaN thin film, characterized in that, include: Substrate; GaN thin film layer, Ga-based liquid metal with GaN film surface covered by a scraping process is printed onto the surface of the substrate; The substrate is selected from at least one of SiO2 / Si wafers, quartz wafers, sapphire wafers, Si wafers, or flexible plastic films. The surface of the substrate is treated with low-temperature plasma. The thickness of the substrate is 50~500µm; The surface roughness Ra of the substrate is ≤0.2µm; The thickness of the GaN thin film layer is 1.4~50 nm; The bandgap of the GaN thin film layer is 3.4~3.6 eV; The melting point of the Ga-based liquid metal is below 40°C; The Ga-based liquid metal comprises, by mass percentage: 20.5-30% metallic In, 0-12.5% ​​metallic Sn, 0-5% metallic Bi, with the balance being metallic Ga.

2. The method for preparing GaN thin films according to claim 1, characterized in that, The preparation method includes: 1) GaN thin films are grown on the surface of Ga-based liquid metal by plasma treatment; 2) Transfer the Ga-based liquid metal obtained in step 1) to the surface of the substrate, spread it on the surface of the substrate, and then remove the Ga-based liquid metal on the substrate to obtain a GaN thin film layer on the substrate surface.

3. The method for preparing GaN thin films according to claim 2, characterized in that, The preparation method further includes: 3) repeating step 2) repeatedly scraping on the surface of the substrate to obtain GaN thin film layers of different thicknesses.

4. The method for preparing GaN thin films according to claim 2, characterized in that, All preparation methods are carried out in an inert atmosphere; The inert atmosphere comprises a mixture of gases containing N2.

5. The method for preparing GaN thin films according to claim 2, characterized in that, In step 1), the surface of the Ga-based liquid metal is free of oxide film; In step 1), the Ga-based liquid metal is treated with low-temperature plasma; In step 1), the low-temperature plasma is formed by exciting a N2-containing mixed gas with a high-voltage electric field.

6. The method for preparing GaN thin films according to claim 2, characterized in that, In step 2), a scraper is used to spread the Ga-based liquid metal with the GaN thin film on the surface of the substrate and let it stand. In step 2), the coating temperature is less than 50℃; In step 2), after removing the Ga-based liquid metal from the substrate, the remaining Ga-based liquid metal on the substrate is further cleaned. In step 2), the surface of the substrate is treated with low-temperature plasma in an atmospheric environment.

7. The application of the GaN thin film according to claim 1 in semiconductor power devices.

8. The application according to claim 7, characterized in that, The semiconductor power device includes at least one of thin-film transistors, PN junction diodes, LEDs, frequency multipliers, and photomultiplier tubes.

9. A thin-film transistor, characterized in that, The thin-film transistor includes the GaN thin film according to claim 1.

10. A PN junction diode, characterized in that, The PN junction diode comprises the GaN thin film as described in claim 1.

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