Aluminum nitride single crystal substrate-gallium-based ordered thin film composite material and preparation method thereof

Abstract

The invention discloses an aluminum nitride single crystal-gallium-based ordered thin film composite material and a preparation method thereof. According to the method, on an aluminum nitride single crystal substrate, a metal gallium thin film is used as a precursor, and an epitaxial gallium oxide or gallium nitride ordered thin film is formed on the surface of the substrate in the controllable oxidation and nitridation process, so that the aluminum nitride single crystal-gallium-based ordered thin film composite material is obtained. The composite material has the high temperature resistance and high thermal conductivity of aluminum nitride and the excellent performance of a gallium-based single crystal film as a microelectronic device, has wide application prospects in the fields of photoelectrons, high-temperature high-power devices and high-frequency microwave devices, and has the advantage of cost performance.

Description

Technical Field

[0001] This invention belongs to the field of functional materials, specifically relating to a gallium-based ordered thin film with aluminum nitride single crystal as a substrate and its preparation method. Background Technology

[0002] The current production of gallium-based semiconductor single crystals basically follows the high-temperature melting and pulling method, which involves melting gallium oxide and gallium nitride powder at high temperature, and then growing gallium oxide and gallium nitride single crystals by pulling pre-placed seed crystals from the crucible. After cutting, gallium oxide and gallium nitride single wafers are obtained.

[0003] This fabrication process is widely used in the production of crystalline materials such as single-crystal silicon, silicon carbide, aluminum nitride, and alumina, but it is not suitable for developing gallium oxide and gallium nitride semiconductor materials. The main reason is that silicon, silicon carbide, aluminum nitride, and alumina semiconductor wafers are readily available and inexpensive, with no limiting factors in supply and demand; while gallium is a rare and dispersed element, with no independent gallium deposits in nature, and it can only be recovered as a byproduct of the aluminum smelting industry. Since the market capacity for metallic aluminum is essentially fixed, neither the demand nor the production of aluminum is likely to increase significantly, and as a byproduct of aluminum, the supply of gallium is also unlikely to increase significantly.

[0004] Gallium's scarcity and refining difficulty keep its price high, and with the widespread application of gallium-based semiconductor materials such as gallium oxide and gallium nitride, its price is expected to rise rapidly. Developing gallium-based semiconductor materials using existing technologies faces challenges in securing raw material supplies and maintaining a competitive price. Replacing three-dimensional single-crystal wafers with two-dimensional ordered thin films represents the future direction for gallium-based semiconductor materials. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of limited production and high cost of gallium oxide single crystal wafers in the prior art, and to provide an aluminum nitride single crystal substrate-gallium-based ordered thin film composite material and its preparation method.

[0006] To achieve the above-mentioned objectives, the specific technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an aluminum nitride single crystal substrate-gallium-based ordered thin film composite material, wherein gallium is orderly distributed on the surface of the aluminum nitride single crystal by means of the lattice breaking of aluminum nitride; during the controllable oxidation and nitriding process, gallium atoms transform into gallium-based compounds and maintain the inheritance of the aluminum nitride crystal structure during the transformation, thereby forming an ordered thin film of epitaxial gallium-based compounds on the substrate surface, constituting an aluminum nitride single crystal substrate-gallium-based ordered thin film composite material; wherein the gallium-based compound is gallium oxide or gallium nitride.

[0007] Secondly, the present invention provides a method for preparing aluminum nitride single-crystal gallium-based ordered thin film composite materials, the preparation steps of which are as follows: First, using a polished and cleaned aluminum nitride single crystal wafer as a thin film substrate, the container containing metallic gallium and the substrate are preheated to 35~50°C until the metallic gallium in the container is completely melted. The liquid metallic gallium is uniformly coated on the substrate surface and excess metallic gallium is scraped or blown off to obtain a gallium-coated substrate. The gallium-coated substrate is placed in a room temperature environment of 15~25°C and slowly cooled until the metallic gallium solidifies, forming a metallic gallium single crystal film on the substrate surface. Then, at a temperature of 0~25℃ and in a preset atmosphere, the substrate covered with a gallium single crystal film is irradiated with ultraviolet light for 1~4 hours, so that the gallium single crystal film is transformed into a gallium-based compound film under solid conditions, and a coated substrate is obtained; the preset atmosphere is an oxygen source gas, and the corresponding gallium-based compound film is a gallium oxide film, or the preset atmosphere is a nitrogen source gas, and the corresponding gallium-based compound film is a gallium nitride film. Finally, the coated substrate is placed in a heating furnace for heat treatment, and heated to the target temperature of 400~900℃ in a carbon dioxide or nitrogen gas flow. After the heat treatment, it is naturally cooled to room temperature to obtain an aluminum nitride single crystal substrate-gallium-based ordered thin film composite material.

[0008] As a preferred embodiment of the second aspect above, the aluminum nitride single crystal wafer is a thin sheet made by cutting and polishing an aluminum nitride single crystal, which is a single crystal formed by crystallizing AlN at high temperature.

[0009] As a preferred embodiment of the second aspect above, the gallium-based ordered thin film is a gallium oxide or gallium nitride thin film, whose molecular arrangement inherits the ordered nature of aluminum nitride single crystals.

[0010] As a preferred embodiment of the second aspect above, the oxygen source gas is oxygen, ozone, or a mixture thereof.

[0011] As a preferred embodiment of the second aspect above, the nitrogen source gas is ammonia.

[0012] As a preferred embodiment of the second aspect above, the heating furnace is an airtight quartz tube furnace or an airtight corundum tube furnace.

[0013] As a preferred embodiment of the second aspect above, the gallium-based compound film is a gallium oxide film, and the ultraviolet light is deep ultraviolet light with a wavelength of 220~255nm, with an irradiation time of 1~2 hours.

[0014] As a preferred embodiment of the second aspect above, the gallium-based compound film is a gallium nitride film, and the ultraviolet light is ultraviolet light with a wavelength of 365~400 nm, with an irradiation time of 3~4 hours.

[0015] As a preferred embodiment of the second aspect above, the heat treatment adopts a gradient heating method until the target temperature is reached, and the temperature is kept constant for 1 to 2 hours at intervals of 100 to 200°C during the heating process, with a cumulative constant temperature time of not less than 6 hours.

[0016] Thirdly, the present invention provides an aluminum nitride single-crystal gallium-based ordered thin film composite material prepared by a preparation method as described in any of the embodiments of the second aspect above.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The high-temperature melt-pulling method for preparing gallium oxide and gallium nitride single crystals suffers from drawbacks such as high raw material consumption, complex processes, and high energy consumption. This invention provides an aluminum nitride single crystal-gallium-based ordered thin film composite material and its preparation method. It involves forming an epitaxial gallium oxide or gallium nitride ordered thin film on an aluminum nitride single crystal substrate using a gallium thin film as a precursor through a controlled oxidation and nitriding process, thereby obtaining the aluminum nitride single crystal-gallium-based ordered thin film composite material. This composite material combines the high temperature resistance and high thermal conductivity of aluminum nitride with the excellent performance of gallium-based single crystal thin films as microelectronic devices, showing broad application prospects in optoelectronics, high-temperature high-power devices, and high-frequency microwave devices, while also offering a cost-effectiveness advantage. Attached Figure Description

[0018] Figure 1 X-ray diffraction pattern of aluminum nitride single crystal substrate; Figure 2 X-ray diffraction pattern of aluminum nitride single crystal substrate-gallium oxide ordered thin film composite material; Figure 3 The X-ray diffraction pattern of the aluminum nitride single crystal substrate-gallium nitride ordered thin film composite material. Detailed Implementation

[0019] The present invention will be further described and illustrated below with reference to specific embodiments. Technical features in various implementations can be combined without conflict, and do not constitute a limitation on the present invention.

[0020] A first aspect of this invention provides an aluminum nitride single-crystal substrate-gallium-based ordered thin film composite material, in which gallium is orderly distributed on the surface of the aluminum nitride single crystal by means of lattice bond breaking of aluminum nitride; in a subsequent controllable transformation process, gallium atoms transform into gallium-based compounds while maintaining the inheritance of the aluminum nitride crystal structure during the transformation, thereby forming an epitaxial gallium-based compound ordered thin film on the substrate surface, constituting an aluminum nitride single-crystal substrate-gallium-based ordered thin film composite material. The gallium-based compound can be gallium oxide or gallium nitride; the controllable transformation process for gallium oxide is a controllable oxidation process, and the controllable transformation process for gallium nitride is a controllable nitriding process.

[0021] Aluminum nitride single crystals are single crystals formed by the crystallization of AlN melt at high temperatures; while thin film substrates are thin slices made by cutting and polishing aluminum nitride single crystals. Aluminum nitride single crystals and the aluminum nitride single crystal slices used as substrates are commercial products, and the cutting, surface polishing, and cleaning techniques for the single crystals are conventional and common techniques. The thickness of the thin film substrate is preferably 0.5~1.5 mm.

[0022] The gallium-based ordered thin film in the above composite material is gallium oxide or gallium nitride thin film, whose molecular arrangement inherits the orderliness of aluminum nitride single crystal.

[0023] Aluminum nitride was chosen as the substrate in this invention because it is a widely available and inexpensive raw material. Aluminum nitride is synthesized by high-temperature calcination of alumina powder with ammonia or nitrogen. Alumina is a major industrial raw material, widely available and inexpensive. Gallium, on the other hand, is a rare and dispersed element, with a global annual production of only a few hundred tons. Replacing gallium oxide and gallium nitride single crystals with aluminum nitride single crystal-gallium-based ordered thin film composites means replacing millimeter-thick wafers with films of nanometer to submicron thickness, significantly reducing gallium usage, ensuring a stable supply of raw materials, and slowing the depletion of this rare resource.

[0024] Gallium-based thin films can be epitaxially grown on aluminum substrates because gallium and aluminum have similar chemical properties. Gallium mainly occurs in aluminum minerals in nature as isomorphous aggregates. The Al-N bonds on the surface of aluminum nitride have a strong affinity and bonding tendency for gallium atoms in gallium-based thin films, which is the basis for the epitaxial growth of gallium-based thin films on aluminum nitride substrates.

[0025] A second aspect of the present invention provides a method for preparing an aluminum nitride single-crystal gallium-based ordered thin film composite material, the steps of which are as follows: 1) Use aluminum nitride single crystal slices cut to an appropriate thickness and with polished and cleaned surfaces as substrates.

[0026] Aluminum nitride single crystals and aluminum nitride single crystal wafers used as substrates are commercial products. The cutting, surface polishing, and cleaning techniques for single crystals are routine and common technologies. Aluminum nitride is heat-resistant and has high thermal conductivity, making it beneficial for heat dissipation and improving the thermal stability of components when used as a substrate for high-power semiconductor materials.

[0027] 2) Preheat the container and substrate containing gallium metal in an oven to 35~50°C until the gallium metal in the container is completely melted. Coat the liquid gallium metal evenly on the surface of the substrate and scrape or blow off the excess gallium metal to obtain a gallium-coated substrate.

[0028] The surface of aluminum nitride single crystal slices contains numerous broken Al-N bonds. Due to the identical valence states and similar ionic radii of aluminum and gallium, the attractive force of the Al-N bonds on the substrate provides the aluminum nitride single crystal surface with bonding force and wettability for liquid gallium, allowing liquid gallium to form a uniformly distributed thin film on the substrate surface. The gallium atoms, constrained by the broken bonds on the substrate surface, exhibit an order consistent with the substrate's lattice arrangement.

[0029] It should be noted that after coating, excess liquid gallium should be scraped or blown away to obtain a film with a thickness of nanometer to submicron and to maintain the stability and consistency of the liquid gallium film thickness.

[0030] 3) Place the gallium-coated substrate at room temperature of 15 to 25°C and slowly cool it until the gallium solidifies to form a gallium single crystal film on the substrate surface.

[0031] Since gallium has a melting point of 29.76°C, slowly cooling the liquid gallium film at a temperature slightly below its melting point allows metallic gallium to solidify into a single-crystal film. This serves as the starting point for subsequent steps involving the in-situ synthesis of ordered gallium-based thin films on an aluminum nitride substrate; the metallic gallium single-crystal film is a precursor for the synthesis of ordered gallium-based thin films.

[0032] 4) Irradiate the substrate covered with a gallium single crystal film with ultraviolet light for 1 to 4 hours at a temperature of 0°C to 25°C and in an atmosphere of oxygen or nitrogen source gas, so that the gallium single crystal film is transformed into a gallium oxide film or a gallium nitride film under solid conditions, and a coated substrate is obtained.

[0033] It is important to note that the choice between oxygen and nitrogen as the source gas in the aforementioned atmosphere determines the type of gallium-based compound film subsequently formed. Gallium-based compound films are either gallium oxide films or gallium nitride films. Specifically, the oxygen source gas is oxygen, ozone, or a mixture thereof; when an oxygen source gas is chosen, it can be used to synthesize gallium oxide thin films. Conversely, the nitrogen source gas is ammonia; when a nitrogen source gas is chosen, it can be used to synthesize gallium nitride thin films.

[0034] When oxygen is chosen as the primary gas, the reaction of the gallium single crystal film with oxygen and ozone is as follows: When nitrogen is chosen as the atmosphere source, the reaction between the gallium single crystal film and ammonia is as follows: Theoretically, gallium can be oxidized by oxygen gas to form gallium oxide and react with ammonia to form gallium nitride, but the reaction rate is slow, and the initial film after surface oxidation and nitridation hinders the reaction from continuing. Ultraviolet light irradiation can promote the forward reaction as shown in equations (1) and (2), which is essentially a photocatalytic effect. The gallium oxide or gallium nitride formed first has a high absorption rate for ultraviolet light, which is converted into chemical energy to accelerate and promote the forward reaction. If the synthesized gallium-based compound film is a gallium nitride film (GaN film), it is recommended to use an ultraviolet light source with a wavelength of 365~400nm and an irradiation time of 3~4 hours; if the synthesized gallium-based compound film is a gallium oxide film (Ga2O3 film), it is recommended to use a deep ultraviolet light source with a wavelength of 220~255nm and an irradiation time of 1~2 hours.

[0035] The system temperature should be kept below the melting point of gallium during ultraviolet irradiation. Ultraviolet irradiation at low temperatures can transform gallium single crystal films into GaN or Ga2O3 films under solid conditions while maintaining their original ordered structure.

[0036] Ultraviolet light is the preferred catalytic reaction light source for this scheme. Of course, theoretically, X-rays and gamma rays can also achieve the same effect, but X-rays and gamma rays are not as convenient to use as ultraviolet light sources.

[0037] 5) Place the coated substrate in a heating furnace for heat treatment, and heat it to the target temperature of 400~900℃ in a carbon dioxide or nitrogen gas flow. After the heat treatment is completed, allow it to cool naturally to room temperature to obtain an aluminum nitride single crystal substrate-gallium-based ordered thin film composite material.

[0038] The heating furnace is an airtight quartz tube furnace or an airtight corundum tube furnace.

[0039] The purpose of heat treatment is to further crystallize the GaN or Ga2O3 film and establish a penetration and fusion relationship with the gallium nitride substrate, thereby improving the adhesion between the ordered film and the substrate. When treating a GaN film-AlN substrate combination, the recommended heating temperature is 400-700°C, using nitrogen as a protective atmosphere to prevent oxidation of the film and substrate. When treating a Ga2O3 film-AlN substrate combination, the recommended heating temperature is 600-900°C, using carbon dioxide gas as a protective atmosphere. CO2 can oxidize residual metallic gallium at high temperatures but will not oxidize the AlN substrate, thus protecting the substrate.

[0040] For the heat treatment process, it is recommended to use a stepped heating method until the target temperature is reached. This means holding the temperature at 100 to 200°C for 1-2 hours at intervals, with a total heating and holding time of no less than 6 hours, preferably no less than 8 hours. The stepped heating method can ensure a relatively stable heat treatment reaction during the heating process and avoid damage to the coating and substrate.

[0041] The aluminum nitride single-crystal substrate-gallium-based ordered thin film composite material proposed in this invention can replace gallium oxide and gallium nitride single-crystal wafers in the field of semiconductor functional materials. This composite material significantly reduces the amount of the rare element gallium used, and the synthesis conditions for epitaxial gallium oxide and gallium nitride ordered thin films are simpler than those for single-crystal wafer preparation, effectively reducing energy consumption and equipment investment. Aluminum nitride is heat-resistant and has high thermal conductivity, which is beneficial for heat dissipation when used as a substrate for high-power integrated circuits, improving the thermal stability of components. Furthermore, aluminum nitride itself is a high-performance semiconductor material. When this substrate is combined with gallium oxide and gallium nitride ordered thin films, a heterojunction can be formed, generating a transistor effect. This means that the aluminum nitride single-crystal-gallium-based ordered thin film composite material can be directly used in high-power semiconductor devices without further doping. In summary, the solution provided by this invention is more cost-effective and competitive in the market compared to gallium oxide and gallium nitride single-crystal wafers.

[0042] The present invention will now be described in detail with reference to the embodiments.

[0043] Example 1 1) Use a 1mm thick aluminum nitride single crystal wafer that has been polished and cleaned as a thin film substrate.

[0044] 2) Preheat the container and substrate containing gallium metal to 50°C in an oven until the gallium metal in the container is completely melted. Coat the liquid gallium metal evenly on the surface of the substrate and scrape or blow off the excess gallium metal to obtain a gallium-coated substrate.

[0045] 3) Place the gallium-coated substrate at room temperature of 25°C and slowly cool it until the metallic gallium solidifies to form a metallic gallium single crystal film on the substrate surface.

[0046] 4) At 0°C and in an oxygen atmosphere, a substrate covered with a gallium single crystal film is irradiated with deep ultraviolet light with a wavelength of 220 to 255 nm for 2 hours, so that the gallium single crystal film is converted into a gallium oxide film under solid conditions, and a coated substrate is obtained.

[0047] 5) The coated substrate was placed in a corundum tube furnace for heat treatment, and heated to 900℃ in a stepwise manner in a carbon dioxide gas stream; during the process, it was kept at 300℃, 400℃, 500℃, 600℃, 700℃, 800℃ and 900℃ for 1 hour each. After the heat treatment was completed, it was naturally cooled to room temperature to obtain an aluminum nitride single crystal substrate-gallium oxide ordered thin film composite material.

[0048] In this embodiment, the X-ray diffraction pattern of the original aluminum nitride single crystal substrate is as follows: Figure 1 As shown, the X-ray diffraction pattern of the finally prepared aluminum nitride single-crystal substrate-gallium oxide ordered thin film composite material is as follows. Figure 2As shown in the figure. The test results show that the gallium oxide film inherits the ordered molecular arrangement of aluminum nitride single crystals. This aluminum nitride single crystal-gallium oxide ordered thin film composite material combines the high temperature resistance and high thermal conductivity of aluminum nitride with the excellent performance of gallium-based single crystal thin films as microelectronic devices, and can be directly used in high-power semiconductor devices without redoping.

[0049] Example 2 1) Use a 0.5mm thick aluminum nitride single crystal wafer that has been polished and cleaned as a thin film substrate.

[0050] 2) Preheat the gallium metal and the substrate in an oven to 35°C until the gallium metal in the container is completely melted. Coat the liquid gallium metal evenly on the substrate surface and blow off the excess gallium metal to obtain a gallium-coated substrate.

[0051] 3) Place the gallium-coated substrate at room temperature of 15°C and slowly cool it until the gallium solidifies to form a gallium single crystal film on the substrate surface.

[0052] 4) At a temperature of 25°C and in an ozone atmosphere, a substrate covered with a gallium single crystal film is irradiated with deep ultraviolet light with a wavelength of 220 to 255 nm for 1 hour, so that the gallium single crystal film is converted into a gallium oxide film under solid conditions, and a coated substrate is obtained.

[0053] 5) The coated substrate was placed in a corundum tube for heat treatment and heated to 600°C in a carbon dioxide gas stream. During the process, the temperature was kept constant at 200°C, 400°C and 600°C for 2 hours each. After the heat treatment was completed, the substrate was naturally cooled to room temperature to obtain an aluminum nitride single crystal substrate-gallium oxide ordered thin film composite material.

[0054] Similarly, as in Example 1, test results show that in the aluminum nitride single crystal-gallium oxide ordered thin film composite material prepared in this example, the molecular arrangement of the gallium oxide thin film inherits the ordered nature of the aluminum nitride single crystal. This aluminum nitride single crystal-gallium oxide ordered thin film composite material combines the high temperature resistance and high thermal conductivity of aluminum nitride with the excellent performance of gallium-based single crystal thin films as microelectronic devices, and can be directly used in high-power semiconductor devices without redoping.

[0055] Example 3 1) Use a 1.5mm thick aluminum nitride single crystal wafer that has been polished and cleaned as a thin film substrate.

[0056] 2) Preheat the container and substrate containing gallium metal in an oven to 40°C until the gallium metal in the container is completely melted. Coat the liquid gallium metal evenly on the surface of the substrate and scrape or blow off the excess gallium metal to obtain a gallium-coated substrate.

[0057] 3) Place the gallium-coated substrate at room temperature of 20°C and slowly cool it until the gallium solidifies to form a gallium single crystal film on the substrate surface.

[0058] 4) At a temperature of 10°C and in an ammonia atmosphere, the substrate covered with a gallium single crystal film is irradiated with ultraviolet light with a wavelength of 365 to 400 nm for 4 hours, so that the gallium single crystal film is converted into a gallium nitride film under solid conditions, and a coated substrate is obtained.

[0059] 5) The coated substrate was placed in a quartz tube for heat treatment and heated to 700°C in an ammonia gas stream. During the heat treatment, the temperature was kept constant at 200°C, 400°C, 600°C and 700°C for 2 hours each. After the heat treatment, the substrate was naturally cooled to room temperature to obtain an aluminum nitride single crystal substrate-gallium nitride ordered thin film composite material.

[0060] In this embodiment, the X-ray diffraction pattern of the original aluminum nitride single crystal substrate is as follows: Figure 1 As shown, the X-ray diffraction pattern of the finally prepared aluminum nitride single-crystal substrate-gallium nitride ordered thin film composite material is as follows. Figure 3 As shown in the figure. The test results show that the gallium nitride thin film inherits the ordered molecular arrangement of aluminum nitride single crystals. This aluminum nitride single crystal-gallium nitride ordered thin film composite material combines the high temperature resistance and high thermal conductivity of aluminum nitride with the excellent performance of gallium-based single crystal thin films as microelectronic devices, and can be directly used in high-power semiconductor devices without redoping.

[0061] Example 4 1) Use a 0.5mm thick aluminum nitride single crystal wafer that has been polished and cleaned as a thin film substrate.

[0062] 2) Preheat the container and substrate containing gallium metal to 45°C in an oven until the gallium metal in the container is completely melted. Coat the liquid gallium metal evenly on the surface of the substrate and scrape or blow off the excess gallium metal to obtain a gallium-coated substrate.

[0063] 3) Place the gallium-coated substrate at room temperature of 22°C and slowly cool it until the gallium solidifies to form a gallium single crystal film on the substrate surface.

[0064] 4) At a temperature of 25°C and in an ammonia atmosphere, the substrate covered with a gallium single crystal film is irradiated with ultraviolet light with a wavelength of 365 to 400 nm for 3 hours, so that the gallium single crystal film is converted into a gallium nitride film under solid conditions, and a coated substrate is obtained.

[0065] 5) The coated substrate was placed in a corundum tube for heat treatment and heated to 400°C in an ammonia gas stream. During the heat treatment, the temperature was kept constant at 100°C, 200°C, 300°C and 400°C for 2 hours each. After the heat treatment, the substrate was naturally cooled to room temperature to obtain an aluminum nitride single crystal substrate-gallium nitride ordered thin film composite material.

[0066] Similarly, as in Example 1, test results show that in the aluminum nitride single crystal-gallium nitride ordered thin film composite material prepared in this example, the molecular arrangement of the gallium nitride thin film inherits the ordered nature of the aluminum nitride single crystal. This aluminum nitride single crystal-gallium nitride ordered thin film composite material combines the high temperature resistance and high thermal conductivity of aluminum nitride with the excellent performance of gallium-based single crystal thin films as microelectronic devices, and can be directly used in high-power semiconductor devices without redoping.

[0067] The embodiments described above are merely some preferred embodiments of the present invention, but are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. An aluminum nitride single-crystal substrate-gallium-based ordered thin film composite material, characterized in that, Gallium is distributed in an ordered manner on the surface of an aluminum nitride single crystal by means of the lattice breaking of aluminum nitride; during the controllable transformation process, gallium atoms transform into gallium-based compounds while maintaining the inheritance of the aluminum nitride crystal structure, thereby forming an ordered epitaxial gallium-based compound film on the substrate surface, constituting an aluminum nitride single crystal substrate-gallium-based ordered film composite material; the gallium-based compound is gallium oxide or gallium nitride, and the controllable transformation process corresponds to a controllable oxidation process and a controllable nitriding process, respectively.

2. A method for preparing an aluminum nitride single-crystal gallium-based ordered thin film composite material, characterized in that, Its preparation steps are as follows: First, using a polished and cleaned aluminum nitride single crystal wafer as a thin film substrate, the container containing metallic gallium and the substrate are preheated to 35~50°C until the metallic gallium in the container is completely melted. The liquid metallic gallium is uniformly coated on the substrate surface and excess metallic gallium is scraped or blown off to obtain a gallium-coated substrate. The gallium-coated substrate is placed in a room temperature environment of 15~25°C and slowly cooled until the metallic gallium solidifies, forming a metallic gallium single crystal film on the substrate surface. Then, at a temperature of 0~25℃ and in a preset atmosphere, the substrate covered with a gallium single crystal film is irradiated with ultraviolet light for 1~4 hours, so that the gallium single crystal film is transformed into a gallium-based compound film under solid conditions, and a coated substrate is obtained; the preset atmosphere is an oxygen source gas, and the corresponding gallium-based compound film is a gallium oxide film, or the preset atmosphere is a nitrogen source gas, and the corresponding gallium-based compound film is a gallium nitride film. Finally, the coated substrate is placed in a heating furnace for heat treatment, and heated to the target temperature of 400~900℃ in a carbon dioxide or nitrogen gas flow. After the heat treatment, it is naturally cooled to room temperature to obtain an aluminum nitride single crystal substrate-gallium-based ordered thin film composite material.

3. The method for preparing aluminum nitride single-crystal-gallium-based ordered thin film composite material as described in claim 2, characterized in that, The aluminum nitride single crystal wafer is a thin sheet made by cutting and polishing aluminum nitride single crystals. Aluminum nitride single crystals are single crystals formed by the crystallization of AlN high-temperature melt.

4. The preparation method according to claim 2, characterized in that, The gallium-based ordered thin film is a gallium oxide or gallium nitride thin film, whose molecular arrangement inherits the ordered nature of aluminum nitride single crystals.

5. The preparation method according to claim 2, characterized in that, The oxygen source gas is oxygen, ozone, or a mixture thereof.

6. The preparation method according to claim 2, characterized in that, The nitrogen source gas is ammonia.

7. The preparation method according to claim 2, characterized in that, The heating furnace is an airtight quartz tube furnace or an airtight corundum tube furnace.

8. The preparation method according to claim 2, characterized in that, The gallium-based compound film is a gallium oxide film, and the ultraviolet light used is deep ultraviolet light with a wavelength of 220~255nm, with an irradiation time of 1~2 hours; or the gallium-based compound film is a gallium nitride film, and the ultraviolet light used is ultraviolet light with a wavelength of 365~400nm, with an irradiation time of 3~4 hours.

9. The preparation method according to claim 2, characterized in that, The heat treatment employs a gradient heating method until the target temperature is reached. During the heating process, the temperature is held constant for 1 to 2 hours at intervals of 100 to 200°C, and the total holding time during the heating process is no less than 6 hours.

10. The aluminum nitride single-crystal gallium-based ordered thin film composite material prepared by the preparation method according to any one of claims 2 to 9.

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