A p-type gallium oxide thin film and a method for preparing the same

Abstract

The application provides a p-type gallium oxide film and a preparation method thereof, and belongs to the technical field of semiconductor materials. The preparation method comprises the following steps: growing a metal M doped beta-(M x Ga 1‑x )2O3 (0.01<=x<=0.15) film on a pre-cleaned beta-Ga2O3 substrate; the metal M is Ir or Cu; the beta-(M x Ga 1‑x )2O3 film is subjected to annealing treatment in an oxygen-deficient environment, and then is subjected to treatment with a supercritical fluid containing nitrogen and having oxidizability, so that the p-type gallium oxide film is obtained. Through the method, the energy and bandwidth of the valence band top of the gallium oxide and the valence band top height can be effectively adjusted, the effective mass of the hole in the valence band top is reduced, the effective doping concentration of nitrogen is improved, and the ionization energy of No is reduced, so that the p-type gallium oxide film with high quality is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor materials, and in particular relates to a p-type gallium oxide thin film and a preparation method thereof. Background Art

[0002] Due to its excellent and stable performance, β-Ga2O3 is widely used in high-power power electronics and solar-blind ultraviolet detection devices. Semiconductor materials are the foundation of device fabrication and determine their performance. Currently, extensive research is devoted to the study of β-Ga2O3 material properties, with a particular focus on p-type doping of β-Ga2O3, which is considered a necessary step for preparing β-Ga2O3-based bipolar devices and improving their performance.

[0003] Doping silicon (Si), tin (Sn), and germanium (Ge) in gallium oxide can easily prepare n-type β-Ga2O3, and the room temperature Hall doping can reach 10 16 -10 20 cm -3 The electron mobility can reach up to 176 cm at room temperature. 2 / V·s. However, p-type gallium oxide that can be used in gallium oxide devices is still difficult to produce. There are three main reasons why it is difficult to achieve p-type doping in β-Ga2O3: (1) The valence band maximum (VBM) of β-Ga2O3 is composed of O with small energy dispersion, large effective mass and high state density. 2p The holes in the VBM are controlled by the orbital, resulting in low hole mobility in the VBM. The holes generated by the p-type metal dopant replacing Ga are easily captured by the O polaron, resulting in the holes in the VBM being unable to move freely. (2) During the β-Ga2O3 crystal growth and thin film epitaxy process, unintentional doping impurities and intrinsic defects form n-type conductivity through ionization, forming a self-compensation effect on the p-type acceptor impurities, making the p-type dopant unable to play the role of an acceptor impurity. (3) The defect formation energy of the p-type dopant during the doping process is high, resulting in a low effective dopant concentration; and because the band gap of β-Ga2O3 is large (4.9eV), the ionization energy of the metal elements that can be doped (Mg, Fe, Zn, etc.) and No is large, and they are deep energy level acceptor impurity defects, which are difficult to ionize at room temperature.

[0004] Prior art 1 "A survey of acceptor dopants for β-Ga2O3" (DOI: 10.1088 / 1361-6641 / aaba98) is a method of doping with metal atoms (see Figure 1 ) prepared p-type gallium oxide, from Figure 1As can be seen from the above, the activation energy of the acceptor impurities in this scheme exceeds 1eV, and it is difficult to ionize at room temperature. In the prior art 2 "A comparison of electronic structure and optical properties between N-dopedβ-Ga2O3 and N-Zn co-dopedβ-Ga2O3" (DOI: 10.1016 / j.phys b.2012.01.107), Zn atoms and nitrogen atoms are co-doped (see Figure 2 In the prior art 3, "Deep level acceptors of Zn-Mg divalent ions dopants inβ-Ga2O3 for the difficulty to p-type conductivity" (DOI: 10.1016 / j.jallcom.2018.12.199), Zn and Mg co-doped p-type gallium oxide was prepared by high temperature oxidation annealing (see Figure 2 (b) Figure); However, the free hole concentration of p-type gallium oxide prepared by these schemes is less than 10 at room temperature. 15 cm -3 , the hole mobility is less than 2 cm 2 / V·s. Prior art 4 "Achieving high conductivity p-type Ga2O3 through Al-N and In-N co-doping" (DOI: 10.1016 / j.cplett.2020.137308) discloses Al / N and In / N co-doping of β-Ga2O3 (see Figure 2 (c) in the middle). Figure 2 It can be seen that although co-doping can reduce the defect formation energy and the ionization energy of the acceptor defect and increase the effective doping concentration, it still cannot avoid the problem of hole self-trapping (i.e., holes are easily captured by O polarons). Prior art 5 "Exploring the feasibility and conduction mechanisms of P-type nitrogen-dopedβ-Ga2O3 with high hole mobility" (DOI: 10.1039 / d1tc05324h) discloses the high-temperature oxidation of GaN in an oxygen atmosphere to generate N-doped p-type gallium oxide thin films ( Figure 3 ), the free hole concentration of p-type gallium oxide at room temperature reached 2.86×10 15 cm -3, the hole mobility reached 41.4 cm 2 / V·s. From Figure 3 As shown in the figure, when using N2 as the doping source, the formation energy of No is very high, indicating its low solubility. Growth under Ga-rich conditions can slightly increase its solubility. However, the p-type GaN produced by this method is achieved by oxidizing GaN onto a silicon / sapphire substrate. Compared to homogeneous GaN epitaxy, this method has a higher defect density. Therefore, its application in power devices has not yet been realized. Summary of the Invention

[0005] Based on the above problems and research progress, the first purpose of the present invention is to provide a method for preparing a p-type gallium oxide film. This method increases the VBM of the gallium oxide film by Ir or Cu doping, bringing it close to the gallium oxide Fermi level; then, a large number of oxygen vacancies (V O ) defects, and then a nitrogen-containing oxidizing supercritical fluid is introduced into the gallium oxide film. The strong oxidizing property of the nitrogen-containing oxidizing supercritical fluid is used to oxidize the Ga dangling bonds to form Ga-N bonds, thereby increasing the effective doping concentration of N and reducing the ionization energy of No, thereby realizing the preparation of p-type gallium oxide.

[0006] Specifically, the present invention adopts the following technical solutions:

[0007] A method for preparing a p-type gallium oxide thin film comprises the following steps:

[0008] S1. Growth of metal M-doped β-(M x Ga 1-x )2O3 thin film; wherein 0.01≤x≤0.15, the metal M is Ir or Cu;

[0009] S2, the β-(M x Ga 1-x )2O3 film was annealed in an oxygen-deficient environment to obtain β-(M x Ga 1-x )2O3 thin film;

[0010] S3, using nitrogen-containing oxidizing supercritical fluid to treat the β-(M x Ga 1-x )2O3 thin film, and obtain nitrogen-heavily doped β-(Ir x Ga 1-x )2O3 film, which is the p-type gallium oxide film.

[0011] In a preferred embodiment, the pre-cleaning method in step S1 is as follows: the unintentionally doped gallium oxide substrate is ultrasonically immersed in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, taken out, rinsed with running deionized water, and blown dry with dry nitrogen.

[0012] In a preferred embodiment, the size of the β-Ga2O3 substrate in step S1 is 2 to 4 inches.

[0013] In a preferred embodiment, in step S1, laser molecular beam epitaxy technology is used to grow metal M-doped β-(M x Ga 1-x )2O3 thin film, the laser wavelength is 1064nm, the pulse width is 10ns, the laser frequency is 10Hz, and the laser energy is 200~300mJ.

[0014] In a further preferred embodiment, the background vacuum is pumped to 1×10 -5 Pa, during sputtering growth, the oxygen partial pressure is 0.5~1Pa.

[0015] In a further preferred embodiment, the distance between the β-Ga2O3 substrate and the target is 40 to 50 mm, and the rotation speeds of the β-Ga2O3 substrate and the target are both 30 rpm.

[0016] In a further preferred embodiment, the temperature of the β-Ga2O3 substrate is 650-1000°C.

[0017] In a further preferred embodiment, a multi-layer sputtering method is adopted to sputter a layer of gallium oxide and then a layer of metal M, and the cycle is repeated multiple times; the sputtering time of each layer of gallium oxide is fixed, and the doping amount of the metal M is controlled by changing the sputtering time of the metal M.

[0018] In a further preferred embodiment, after the sputtering is completed, annealing is performed at 800-1000° C. for 30-60 minutes in an argon atmosphere, with the flow rate of the argon gas preferably being 100 sccm.

[0019] In a preferred embodiment, the specific steps of the annealing treatment in an oxygen-deficient environment in step S2 are: treating at 600-700° C. for 45-60 min in an inert gas atmosphere with an oxygen volume percentage of 0-5%.

[0020] In a preferred embodiment, the concentration of oxygen vacancies in step S2 is 10 18 ~10 20 .

[0021] In a preferred embodiment, the nitrogen-containing oxidizing supercritical fluid in step S3 includes NO and / or N2O.

[0022] When the nitrogen-containing oxidizing supercritical fluid is N2O, the treatment method in step S3 is as follows: N2O is converted into a supercritical fluid state and introduced into a β-(Cu x Ga 1-x )2O3 film in a sealed chamber at 120℃~200℃ and pressure ≥7.26MPa for 60~90min.

[0023] When the nitrogen-containing oxidizing supercritical fluid is NO, the treatment method in step S3 is as follows: NO is converted into a supercritical fluid state and introduced into a β-(Cu x Ga 1-x )2O3 film in a sealed chamber at room temperature and a pressure ≥0.66MPa for 60min.

[0024] A second object of the present invention is to provide a p-type gallium oxide thin film prepared according to any of the above methods for preparing a p-type gallium oxide thin film, wherein the thickness of the p-type gallium oxide thin film is 100 to 500 nm.

[0025] Compared with the prior art, the present invention has the following advantages: (1) In the present invention, Ir or Cu atoms are first introduced into β-Ga2O3, so that the metal atoms replace the tetrahedral coordinated Ga(I) and octahedral coordinated Ga(II). Since the atoms are similar in size, no large lattice distortion is generated, thereby adjusting the energy and bandwidth of the gallium oxide VBM and reducing the effective mass of the holes in the gallium oxide VBM. (2) In the present invention, the VBM height of β-Ga2O3 is adjusted to make the acceptor impurity N O The ionization energy of the defect is relatively low, and N 2p Orbital above O 2P orbital, N can adsorb the generated holes, avoiding the localization of holes by O polarons, thereby realizing the preparation of p-type gallium oxide. (3) In the present invention, a nitrogen-containing oxidizing supercritical fluid is used to oxidize Ga dangling bonds to form Ga-N bonds, thereby increasing the effective doping concentration of N and reducing the ionization energy of No, thereby realizing the preparation of p-type gallium oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The defect energy level diagram of N, Be, Mg, Ca, Sr, Zn, and Cd acceptor impurities in the acceptor atom-doped β-Ga2O3 in the prior art 1;

[0027] Figure 2Figure (a) is a defect energy level diagram of N and Zn co-doping in β-Ga2O3 in prior art 2; Figure (b) is a defect energy level diagram of Zn and Mg co-doping in β-Ga2O3 in prior art 3; Figure (c) is a defect energy level diagram of Al / N and In / N co-doping in β-Ga2O3 in prior art 4;

[0028] Figure 3 (a) Figure 5 shows the N2 dopant source or the N2 dopant of β-Ga2O3 in a thermal oxidation atmosphere at high temperature in the prior art 5. O Defect formation energy changes with oxygen atmosphere; (b) and (c) are diagrams showing the relationship between the N2 as a dopant source or the N of β-Ga2O3 achieved by structural phase transition in prior art 5. O Defect formation energy and Fermi level relationship diagram; (d) Figure 5 shows the N2 as a dopant source or the N of β-Ga2O3 achieved by structural phase transition in the prior art O Ionization energy diagram of defects;

[0029] Figure 4 This is a flow chart for preparing the p-type gallium oxide thin film in the present invention. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the embodiments, so that those skilled in the art can fully understand the present invention. Obviously, the embodiments described are only some preferred embodiments of the present invention, rather than all embodiments. Any equivalent transformations or substitutions made by those skilled in the art to the following embodiments without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 4 As shown, this embodiment provides a method for preparing a p-type gallium oxide thin film by regulating the valence band top of gallium oxide by iridium doping, comprising the following steps:

[0033] S1. Use physical vapor deposition (such as laser molecular beam epitaxy, LMBE) to grow metal M-doped β-(Ir x Ga 1-x )2O3 (0.016≤x≤0.125) film, regulating the valence band top of the β-Ga2O3 film. The specific method is as follows: take a 3-inch non-intentionally doped gallium oxide substrate, soak it in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, take it out and rinse it with flowing deionized water, and blow it dry with dry nitrogen. Start the molecular pump to vacuum the LMBE growth chamber, fix the cleaned gallium oxide substrate in the LMBE growth chamber with the growth surface facing down, stop the molecular pump, and the vacuum degree is less than 10-8 mbar, then laser molecular beam epitaxy was performed using a 99.99% gallium oxide ceramic target and a 99.99% iridium target to grow iridium-doped gallium oxide thin films. A Nd:YAG laser was used as the laser light source with an excitation wavelength of 1064 nm, a pulse width of 10 ns, a laser frequency of 10 Hz, and a laser energy of 200 mJ. Before film growth, the background vacuum was evacuated to 1×10 -5 During sputtering growth, the oxygen partial pressure was 0.8 Pa, the distance between the substrate and the target was 45 mm, the rotation speed of the substrate and target was 30 rpm, and the substrate temperature was 800°C. A multilayer sputtering method was used, with a layer of gallium oxide followed by a layer of iridium sputtered in multiple cycles. The sputtering time for each gallium oxide layer was fixed at 5 minutes, resulting in a total of four gallium oxide layers and three iridium layers, with a gallium oxide sputtering time of 4 × 5 minutes. The target was then rotated to sputter the iridium target. By varying the sputtering time of the iridium target over three times, the iridium doping level was controlled between 0.016 and 0.125. The resulting p-type gallium oxide doped film had a thickness of 300 nm. Finally, the film was annealed at 900°C for 45 minutes in a diffusion furnace with an Ar flow rate of 100 sccm.

[0034] S2, Ir-doped β-(Ir x Ga 1-x )2O3 thin film was annealed to obtain β-(Ir x Ga 1-x )2O3 film. The specific method is as follows: β-(Ir x Ga 1-x )2O3 film was placed in a sealed chamber and annealed at 700℃ in an argon atmosphere containing 5 (v / v)% oxygen for 60 min, so that oxygen atoms were transferred from β-(Ir x Ga 1-x )2O3 diffuses out of the lattice to form oxygen vacancies V O , oxygen vacancies V in an oxygen-deficient environment O The defect formation energy is reduced and Vo is more likely to form. After the annealing treatment is completed, the β-(Ir x Ga 1-x )2O3 film was taken out and quickly cooled to room temperature, which can freeze the oxygen vacancies generated at high temperature. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed that the concentration of oxygen vacancy defects was 10 18 ~10 20 between.

[0035] S3, using nitrogen-containing oxidizing supercritical fluid to treat the β-(Ir-2-ylidene pyrite) containing oxygen vacancies obtained in step S2 x Ga 1-x )2O3 thin film, and obtain nitrogen-heavily doped β-(Ir xGa 1-x )2O3 film. The specific method is as follows: N2O (critical temperature TC = 36.5 ° C, critical pressure PC = 7.26 MPa) is transformed into a supercritical fluid state and introduced into a β-(Ir x Ga 1-x )2O3 film in a sealed chamber at 200℃ and pressure ≥7.26MPa for 60min to oxidize the gallium dangling bonds at the oxygen vacancies and realize the nitrogen-heavily doped β-(Ir x Ga 1-x )2O3 thin film.

[0036] Example 2

[0037] This embodiment provides a method for preparing a p-type gallium oxide thin film by regulating the valence band top of gallium oxide by iridium doping, comprising the following steps:

[0038] S1, using physical vapor deposition (such as laser molecular beam epitaxy, LMBE) to grow Ir-doped β-(Ir x Ga 1-x )2O3 (0.016≤x≤0.125) film, and regulate the valence band top of the β-Ga2O3 film. The specific method is as follows: take a 2-inch non-intentionally doped gallium oxide substrate, ultrasonically soak it in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, take it out and rinse it with flowing deionized water, and blow it dry with dry nitrogen. Start the molecular pump to vacuum the LMBE growth chamber, fix the cleaned gallium oxide substrate in the LMBE growth chamber with the growth surface facing down, stop the molecular pump, and the vacuum degree is less than 10 -8 mbar, and then laser molecular beam epitaxy was performed on 99.99% gallium oxide ceramic targets and 99.99% iridium targets to grow iridium-doped gallium oxide thin films. Nd:YAG laser was used as the laser light source with an excitation wavelength of 1064nm, a pulse width of 10ns, a laser frequency of 10Hz, and a laser energy of 200mJ. Before film growth, the background vacuum was evacuated to 1×10 -5 During sputtering growth, the oxygen partial pressure was 0.5 Pa, the distance between the substrate and the target was 40 mm, the rotation speed of the substrate and target was 30 rpm, and the substrate temperature was 650°C. A multilayer sputtering method was used, with a layer of gallium oxide followed by a layer of iridium sputtered in multiple cycles. The sputtering time for each gallium oxide layer was fixed at 5 minutes, resulting in a total of four gallium oxide layers and three iridium layers, with a sputtering time of 4 × 5 minutes for each gallium oxide layer. The target was then rotated to sputter the iridium target. By varying the sputtering time of the iridium target over three times, the iridium doping level was controlled between 0.016 and 0.125. The resulting p-type gallium oxide doped film had a thickness of 350 nm. Finally, the film was annealed at 800°C for 60 minutes in a diffusion furnace with an Ar flow rate of 100 sccm.

[0039] S2, Ir-doped β-(Ir x Ga 1-x )2O3 thin film was annealed to obtain β-(Ir x Ga 1-x )2O3 film. The specific method is as follows: β-(Ir x Ga 1-x )2O3 film was placed in a sealed equipment chamber and annealed at 650℃ in an argon atmosphere containing 3 (v / v)% oxygen for 50 min, so that oxygen atoms were transferred from β-(Ir x Ga 1-x )2O3 diffuses out of the lattice to form oxygen vacancies V O , oxygen vacancies V in an oxygen-deficient environment O The defect formation energy is reduced and Vo is more likely to form. After the annealing treatment is completed, the β-(Ir x Ga 1-x )2O3 film was taken out and quickly cooled to room temperature, which can freeze the oxygen vacancies generated at high temperature. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed that the concentration of oxygen vacancy defects was 10 18 ~10 20 between.

[0040] S3, using nitrogen-containing oxidizing supercritical fluid to treat the oxygen vacancy-rich β-(Ir x Ga 1-x )2O3 thin film, and obtain nitrogen-heavily doped β-(Ir x Ga 1-x )2O3 film. The specific method is as follows: NO (critical temperature TC = -93 ° C, critical pressure PC = 0.66 MPa) is transformed into a supercritical fluid state and introduced into a β-(Ir x Ga 1-x )2O3 film in a sealed chamber at room temperature and a pressure of ≥0.66MPa for 60min to oxidize the gallium dangling bonds at the oxygen vacancies and achieve nitrogen-heavy doped β-(Ir x Ga 1-x )2O3 thin film.

[0041] Example 3

[0042] This embodiment provides a method for preparing a p-type gallium oxide thin film by regulating the valence band top of gallium oxide by copper (Cu) doping, comprising the following steps:

[0043] S1. Cu-doped β-(Cu)-doped β-Ga2O3 was grown on β-Ga2O3 substrate by physical vapor deposition (such as laser molecular beam epitaxy, LMBE). x Ga1-x )2O3 (0.01≤x≤0.15) film, regulating the valence band top of the β-Ga2O3 film. The specific method is as follows: take a 4-inch non-intentionally doped gallium oxide substrate, ultrasonically soak it in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, take it out and rinse it with flowing deionized water, and blow it dry with dry nitrogen. Start the molecular pump to vacuum the LMBE growth chamber, fix the cleaned gallium oxide substrate in the LMBE growth chamber with the growth surface facing down, stop the molecular pump, and the vacuum degree is less than 10 -8 mbar, and then a copper-doped gallium oxide film was grown by laser molecular beam epitaxy using a 99.99% gallium oxide ceramic target and a 99.99% copper target. A Nd:YAG laser was used as the laser light source with an excitation wavelength of 1064nm, a pulse width of 10ns, a laser frequency of 10Hz, and a laser energy of 300mJ. Before film growth, the background vacuum was evacuated to 1×10 -5 During sputtering growth, the oxygen partial pressure was 1 Pa, the distance between the substrate and the target was 50 mm, the rotation speed of the substrate and target was 30 rpm, and the substrate temperature was 1000°C. A multilayer sputtering method was used, with a layer of gallium oxide followed by a layer of iridium, repeated multiple times. The sputtering time for each gallium oxide layer was fixed at 5 minutes, resulting in four gallium oxide layers and three copper layers, with a gallium oxide sputtering time of 4 × 5 minutes. The target was then rotated to sputter the copper target. The copper doping level was controlled between 0.01 and 0.15 by varying the sputtering time of the copper target over three passes. The resulting p-type gallium oxide doped film had a thickness of 100 nm. Finally, the film was annealed at 1000°C for 30 minutes in a diffusion furnace with an Ar flow rate of 100 sccm.

[0044] S2, Cu-doped β-(Cu x Ga 1-x )2O3 thin film was annealed to obtain β-(Cu x Ga 1-x )2O3 film. The specific method is as follows: β-(Cu x Ga 1-x )2O3 film was placed in a sealed equipment chamber and annealed at 650℃ in an argon atmosphere for 45min, so that oxygen atoms were removed from β-(Cu x Ga 1-x )2O3 diffuses out of the lattice to form oxygen vacancies V O , oxygen vacancies V in an oxygen-deficient environment O The defect formation energy is reduced and Vo is more likely to form. After the annealing treatment is completed, the β-(Cu x Ga 1-x)2O3 film was taken out and quickly cooled to room temperature, which can freeze the oxygen vacancies generated at high temperature. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed that the concentration of oxygen vacancy defects was 10 18 ~10 20 between.

[0045] S3, introduce supercritical fluid N2O to oxidize gallium dangling bonds to obtain N-heavily doped β-(Cu x Ga 1-x )2O3 film. The specific method is as follows: N2O is converted into a supercritical fluid state and introduced into a β-(Cu x Ga 1-x )2O3 film in a sealed chamber at 120℃ and pressure ≥7.26MPa for 90min to oxidize the gallium dangling bonds at the oxygen vacancies and realize the N-heavily doped β-(Cu x Ga 1-x )2O3 thin film.

[0046] Example 4

[0047] This embodiment provides a method for preparing a p-type gallium oxide thin film by regulating the valence band top of gallium oxide by copper doping, comprising the following steps:

[0048] S1, using physical vapor deposition (laser molecular beam epitaxy, LMBE) to grow Cu-doped β-(Cu x Ga 1-x )2O3 (0.01≤x≤0.15) film, regulating the valence band top of the β-Ga2O3 film. The specific method is as follows: take a 4-inch non-intentionally doped gallium oxide substrate, ultrasonically soak it in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, take it out and rinse it with flowing deionized water, and blow it dry with dry nitrogen. Start the molecular pump to vacuum the LMBE growth chamber, fix the cleaned gallium oxide substrate in the LMBE growth chamber with the growth surface facing down, stop the molecular pump, and the vacuum degree is less than 10 -8 mbar, and then a copper-doped gallium oxide film was grown by laser molecular beam epitaxy using a 99.99% gallium oxide ceramic target and a 99.99% copper target. A Nd:YAG laser was used as the laser light source with an excitation wavelength of 1064nm, a pulse width of 10ns, a laser frequency of 10Hz, and a laser energy of 300mJ. Before film growth, the background vacuum was evacuated to 1×10 -5During sputtering growth, the oxygen partial pressure was 0.7 Pa, the distance between the substrate and the target was 45 mm, the rotation speed of the substrate and target was 30 rpm, and the substrate temperature was 900°C. A multi-layer sputtering method was used, with a layer of gallium oxide followed by a layer of copper, repeated multiple times. The sputtering time for each gallium oxide layer was fixed at 5 minutes, resulting in four gallium oxide layers and three copper layers, with a gallium oxide sputtering time of 4 × 5 minutes. The target was then rotated to sputter the copper target. By varying the copper target's sputtering time over the three times, the copper doping level was controlled between 0.01 and 0.15. The resulting p-type gallium oxide-doped film had a thickness of 500 nm. Finally, the film was annealed at 900°C for 50 minutes in a diffusion furnace with an Ar flow rate of 100 sccm.

[0049] S2, Cu-doped β-(Cu x Ga 1-x )2O3 thin film was annealed to obtain β-(Cu x Ga 1-x )2O3 film. The specific method is as follows: β-(Cu x Ga 1-x )2O3 film was placed in a sealed chamber and annealed at 600℃ in an argon atmosphere containing 5 (v / v)% oxygen for 60 minutes, so that oxygen atoms were removed from β-(Cu x Ga 1-x )2O3 diffuses out of the lattice to form oxygen vacancies V O , oxygen vacancies V in an oxygen-deficient environment O The defect formation energy is reduced and Vo is more likely to form. After the annealing treatment is completed, the β-(Cu x Ga 1-x )2O3 is taken out and quickly cooled to room temperature, which can freeze the oxygen vacancies generated at high temperature. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy determine that the concentration of oxygen vacancy defects is 10 18 ~10 20 between.

[0050] S3, introduce supercritical fluid NO to oxidize β-(Cu x Ga 1-x )2O3, and obtain N-heavily doped β-(Cu x Ga 1-x )2O3 film. The specific method is as follows: NO is converted into a supercritical fluid state and introduced into a β-(Cu x Ga 1-x )2O3 film in a sealed chamber at room temperature and a pressure of ≥0.66MPa for 60min to oxidize the gallium dangling bonds at the oxygen vacancies and achieve N-heavily doped β-(Cu x Ga 1-x)2O3 thin film.

[0051] Example 5

[0052] The method for preparing p-type gallium oxide thin film by iridium doping and regulating the valence band top of gallium oxide in this embodiment is basically the same as that in embodiment 1. The difference is that in step S3, a nitrogen-containing oxidizing supercritical fluid is used to treat the β-(Ir-2-thiophene) containing oxygen vacancies obtained in step S2. x Ga 1-x )2O3 film is as follows: N2O is converted into a supercritical fluid state and introduced into a β-(Ir x Ga 1-x )2O3 film in a sealed chamber at 160℃ and pressure ≥7.26MPa for 75min to oxidize the gallium dangling bonds at the oxygen vacancies and realize the nitrogen-heavy doped β-(Ir x Ga 1-x )2O3 thin film.

[0053] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It will be apparent to anyone skilled in the art that various modifications and variations of the present invention are possible. Any simple equivalent variations and modifications made in accordance with the scope of protection of the present invention and the contents of the specification are intended to be included within the scope of protection of the present invention.

Claims

1. A method for preparing a p-type gallium oxide thin film, characterized in that: The following steps are involved: S1. Growth of metal M-doped β-(M x Ga 1-x )2O3 thin film; wherein 0.01≤x≤0.15, the metal M is Ir or Cu; S2, the β-(M x Ga 1-x )2O3 film was annealed in an oxygen-deficient environment to obtain β-(M x Ga 1-x )2O3 thin film; S3, using nitrogen-containing oxidizing supercritical fluid to treat the β-(M x Ga 1-x )2O3 thin film, and obtain nitrogen-heavily doped β-(M x Ga 1-x )2O3 film, namely the p-type gallium oxide film; the nitrogen-containing oxidizing supercritical fluid is NO or N2O; when the nitrogen-containing oxidizing supercritical fluid is N2O, the treatment method is as follows: converting N2O into a supercritical fluid state and introducing it into a β-(M x Ga 1-x )2O3 film in a sealed chamber at 120℃~200℃ and pressure ≥7.26MPa for 60~90min; when the nitrogen-containing oxidizing supercritical fluid is NO, the treatment method is as follows: NO is converted into a supercritical fluid state and introduced into a chamber containing β-(M x Ga 1-x )2O3 film in a sealed chamber at room temperature and a pressure ≥0.66MPa for 60min.

2. The method for preparing a p-type gallium oxide thin film according to claim 1, wherein: In step S1, laser molecular beam epitaxy technology is used to grow metal M-doped β-(M x Ga 1-x )2O3 thin film, the laser wavelength is 1064nm, the pulse width is 10ns, the laser frequency is 10Hz, and the laser energy is 200~300mJ.

3. The method for preparing a p-type gallium oxide thin film according to claim 2, wherein: Before film growth, the background vacuum was pumped to 1×10 -5 Pa, during sputtering growth, the oxygen partial pressure is 0.5~1Pa.

4. The method for preparing a p-type gallium oxide thin film according to claim 2, wherein: The distance between the β-Ga2O3 substrate and the target is 40-50 mm, the rotation speeds of the β-Ga2O3 substrate and the target are both 30 rpm; or / and the temperature of the β-Ga2O3 substrate is 650°C-1000°C.

5. The method for preparing a p-type gallium oxide thin film according to claim 2, wherein: A multi-layer sputtering method is adopted to sputter a layer of gallium oxide and then a layer of metal M, and the cycle is repeated multiple times; the sputtering time of each layer of gallium oxide is fixed, and the doping amount of the metal M is controlled by changing the sputtering time of the metal M.

6. The method for preparing a p-type gallium oxide thin film according to claim 2, wherein: After sputtering, annealing was performed at 800-1000°C for 30-60 min in an argon atmosphere.

7. The method for preparing a p-type gallium oxide thin film according to claim 1, wherein: The specific steps of the annealing treatment in the oxygen-deficient environment in step S2 are: treating at 600-700° C. for 45-60 minutes in an inert gas atmosphere with an oxygen volume percentage of 0-5%.

8. The method for preparing a p-type gallium oxide thin film according to claim 1, wherein: The concentration of oxygen vacancies in step S2 is 10 18 ~10 20 .

9. A p-type gallium oxide thin film prepared by the method for preparing a p-type gallium oxide thin film according to any one of claims 1 to 8.

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