Annealing process for p-type beta-Ga2O3 film

Abstract

The invention relates to the technical field of semiconductor material preparation, in particular to an annealing process of a p-type beta-Ga2O3 single crystal thin film, which accurately regulates lattice defects of a gallium oxide thin film and inhibits formation of oxygen vacancies through a multi-stage atmosphere regulation and temperature gradient optimization technology. Under the action of the annealing atmosphere, non-metallic elements are guided to replace oxygen elements in gallium oxide crystal lattices, p-type conductive characteristics are formed, the hole concentration and the crystal quality of the gallium oxide thin film are improved, and finally the high-quality p-type beta-Ga2O3 single crystal thin film which is controllable in size and thickness and remarkable in Hall effect is obtained. By controlling the annealing time, the hole mobility of the thin film can reach up to 18 cm / V.s, the hole concentration can reach up to 5.0 * 10 < 16 > cm <->, and a solid foundation is laid for practical application of next-generation power devices and deep ultraviolet light detectors.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials and thin film preparation technology. More specifically, the purpose of this invention is to provide a method for p-type... β Annealing process for Ga2O3 single crystal thin films. Background Technology

[0002] β Ga2O3 is a semiconductor material with an ultra-wide bandgap (4.9 eV), high breakdown electric field strength (8 MV / cm), and excellent chemical and thermal stability, and is therefore widely considered an ideal candidate material for next-generation power devices and deep ultraviolet photodetectors [Zhang. J. C, et al., “Ultra-wide bandgap semiconductor Ga2O3 powerdiodes.” Nat. Commun. 2022, 13, 3900]. However, due to its intrinsic oxygen vacancy defects and the tendency for shallow-level impurities to form near the conduction band, β Ga₂O₃ typically exhibits as an n-type oxide semiconductor [Guo. D. Y, et al., “Review of Ga₂O₃ based optoelectronic devices.” Mater. Today. Phys. 2019. 11. 100157]. Furthermore, p-type doping can be achieved due to its high acceptor ionization energy (>200 meV), self-compensation effect, extremely low hole mobility, and hole trapping effect. β -Ga2O3 is extremely challenging, which largely limits the application of Ga2O3-based technologies. β -Integration development of Ga2O3 devices.

[0003] To achieve p-type β Researchers have explored various approaches to Ga2O3. For example, some researchers have attempted to introduce divalent cations (such as Cu, Zn, and Mg) as acceptor impurities into the matrix. β -Ga2O3 [Zhang. Y. et al., Optical and structural properties of Cu-doped β -Ga2O3films. Mater. Sci. Eng. B 2011. 176. 846-849]. However, due to the significant self-compensation effect, the resulting hole concentration is usually low (approximately 10). 10 -10 13 cm -3 Recently, research has successfully obtained p-type GaN through high-temperature thermal oxidation. β-Ga2O3 thin films, with a hole mobility of up to 23.6 cm⁻¹. 2 V -1 s -1 The hole concentration is approximately 1.56 × 10⁻⁶. 16 cm -3 [Qin. Y. et al., Review of deep ultraviolet photodetector based on gallium oxide. Chin. Phys. B 2019. 28. 018501]. However, due to GaN and... β There is a large lattice mismatch between Ga₂O₃ and the material prepared by this method... β -Ga2O3 thin films have a polycrystalline structure, which is not conducive to the subsequent fabrication of junction structures and device integration.

[0004] Epitaxial annealing in an oxygen atmosphere is also a commonly used method; however, the p-type properties of the films obtained by this method are still relatively weak, with hole mobility and hole concentration only about 0.4 cm⁻¹. 2 ·V -1 ·s -1 and 2.0×10 14 cm -3 This severely limits further improvements in the performance of related devices [Chikoidze, E. et al., P-type β-gallium oxide: A new perspective for power and optoelectronic devices. Mater. Today.Phys. 2017. 3. 118-126]. Some domestic researchers have also optimized the gallium oxide nucleation and crystallization process by implementing staged temperature control during the annealing process, avoiding technical problems such as film shrinkage and uneven film surface caused by rapid heating.

[0005] Against this backdrop, it is necessary to develop a method that can effectively regulate β Annealing processes that reveal the properties of Ga2O3 thin films to achieve efficient p-type doping and improve hole mobility and concentration while maintaining the high-quality single-crystal structure of the film have become an urgent need for current technological development. Summary of the Invention

[0006] To overcome the various shortcomings of the prior art, the present invention provides a p-type... β The annealing process for Ga2O3 single-crystal thin films aims to improve performance by optimizing the annealing atmosphere, temperature gradient control, pressure conditions, and interface modification techniques, combined with specific pretreatment and post-treatment steps. βThe hole concentration and mobility of Ga2O3 thin films are improved, while their crystal quality is enhanced, thereby meeting the requirements of high-performance p-type semiconductor devices and driving... β - Further development of Ga2O3-based devices.

[0007] According to one aspect of the invention, a method for p-type is provided. β - An annealing process for Ga2O3 single crystal thin films: This method involves placing the gallium oxide thin film in an annealing furnace, purging the furnace chamber with an inert gas or a mixture of an inert gas and a gas containing doped non-metallic elements, then introducing an annealing atmosphere gas and annealing at a specified temperature. Afterwards, the annealing atmosphere is maintained, and the film is cooled to room temperature. Doped p-type Ga2O3 is obtained by replacing the oxygen elements in the gallium oxide lattice with non-metallic elements. β -Ga2O3 single crystal thin film.

[0008] In one embodiment of the present invention, the gallium oxide thin film is obtained using a conventional thin film growth method in the art, wherein the substrate used to grow the gallium oxide thin film includes any one selected from aluminum oxide, strontium titanate, gallium oxide, silicon, silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

[0009] Preferably, when the substrate is alumina, an alumina single crystal substrate with an orientation

[0001] direction is selected.

[0010] In another embodiment of the present invention, the inert gas is an oxygen-free gas, selected from argon, helium, and nitrogen.

[0011] In another embodiment of the present invention, the doped nonmetallic element is selected from elements such as nitrogen, fluorine, and chlorine, with nitrogen being preferred. The annealing atmosphere containing the doped nonmetallic element can be determined by those skilled in the art by comprehensively considering material characteristics, process objectives, and equipment tolerance. Commonly selected elements include ammonia, nitrogen fluoride, carbon trifluoride, carbon tetrafluoride, chlorine, and carbon tetrachloride, with ammonia being preferred.

[0012] In another embodiment of the present invention, in the mixture of the inert gas and the oxygen-free gas containing doped non-metallic elements, the volume fraction of the oxygen-free gas containing doped non-metallic elements is 10% to 20%, and the volume fraction of the inert gas is 80% to 90%.

[0013] In another embodiment of the present invention, the specified annealing temperature is 300~800 °C, the heating rate is 3 to 8 °C per minute, and the annealing time is 10 minutes to 3 hours, so as to ensure that the lattice stress inside the film is fully released.

[0014] Optionally, the heating rate in the annealing furnace chamber is set in stages. First, the temperature is raised from room temperature to 450 °C at a rate of 3 to 5 °C per minute and held for at least 20 minutes. Then, the temperature is raised to 600 to 800 °C at a rate of 5 to 8 °C per minute and held for 40 minutes to 3 hours. Annealing under these conditions can activate acceptor impurities to the greatest extent while avoiding material damage caused by excessively high temperature or excessive time.

[0015] In another embodiment of the invention, the pressure inside the annealing furnace chamber is maintained between atmospheric pressure and 1.2 atmospheres to avoid excessive pressure from damaging the film surface.

[0016] Optionally, the pressure inside the annealing furnace chamber is set in stages, with an initial pressure of 0.1 to 0.5 atmospheres, gradually increasing to 0.8 to 1.2 atmospheres during the heating process. By gradually adjusting the pressure inside the annealing furnace chamber, the contact efficiency between atmosphere molecules and the film surface can be further optimized, thereby improving the annealing effect.

[0017] In another embodiment of the invention, during the cooling process to room temperature, the cooling rate is preferably 4 to 10 °C per minute, and the stability of the atmosphere inside the chamber is continuously monitored during the cooling process.

[0018] In another embodiment of the present invention, annealing of gallium oxide thin films is achieved by ultraviolet light irradiation, wherein the wavelength of the ultraviolet light is 250 nm to 400 nm and the irradiation power is 10 to 200 mW / cm². 2 During annealing, ultraviolet light directly excites valence band electron transitions in gallium oxide, generating a large number of electron-hole pairs, creating active sites for the introduction of nitrogen atoms. The energy provided by ultraviolet light can lower the activation energy of the nitrogen substitution for oxygen process, which helps to locally adjust and reorganize the lattice near the doped region, allowing the reaction to proceed effectively at relatively low temperatures. Therefore, it helps to suppress the formation of oxygen vacancies at high temperatures, promotes the more stable occupation of oxygen sites by nitrogen atoms, and forms effective acceptor centers.

[0019] According to a second aspect of the invention, the invention also provides a method for optimizing β A method for distributing acceptor impurities in Ga2O3 thin films involves introducing divalent metal cations into the gallium oxide film and precisely controlling the doping concentration of the metal cations and the nitrogen content in the annealing atmosphere. This effectively improves the ionization efficiency of acceptor impurities and reduces the hole trapping effect, thereby achieving high-concentration and high-mobility p-type conductivity. The method specifically includes the following steps: T10: During the initial β-Ga2O3 thin film deposition process, divalent metal cations were used as acceptor impurities, with a doping concentration of 10. 18 ~1020 cm -3 ; T20: During the annealing process, the ionization and activation of divalent metal cations are promoted by adjusting the nitrogen content in the annealing atmosphere.

[0020] In one embodiment of the present invention, in step T10, the doping concentration of the divalent metal cation is preferably 10. 19 ~10 20 cm -3 This is to ensure a sufficient amount of acceptor impurities.

[0021] In another embodiment of the present invention, in step T20, annealing is performed in a mixed atmosphere, and the volume fraction of nitrogen is adjusted to 10% to 30% in the early stage of annealing and gradually increased to 40% to 50% in the later stage of annealing, so as to gradually activate magnesium ions and reduce damage to the film structure.

[0022] In another embodiment of the present invention, in step T20, annealing is carried out in a mixed atmosphere, and the volume fraction of ammonia is adjusted to 1% to 3% in the early stage of annealing and gradually increased to 10% to 20% in the later stage of annealing, so as to precisely control the occupancy rate of divalent metal ions and the oxygen concentration in the gallium oxide thin film lattice.

[0023] According to a third aspect of the invention, a method for evaluating annealed products is also provided. β The technical means to improve the performance of Ga2O3 thin films specifically include the following steps: U10: The surface morphology and elemental surface scans of the thin film were observed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The scanning range of scanning electron microscopy (SEM) is from a few micrometers to tens of millimeters, and the resolution is less than 1 nanometer. The spatial resolution of energy-dispersive X-ray spectroscopy (EDS) is generally better than 50 nm, and the energy resolution is generally between 125 eV and 133 eV. U20: The crystal structure of the thin film was analyzed using an X-ray diffractometer with a scanning angle range of 10 degrees to 70 degrees and a step size of 0.01 degrees to 0.05 degrees. U30: The absorbance and bandgap fitting of gallium oxide thin films were tested using a UV-Vis-NIR spectrophotometer, with a test wavelength range of 200 to 1200 nm. U40: Hole concentration and mobility of the annealed film were measured using a Hall effect tester at temperatures ranging from room temperature to 300 °C.

[0024] According to the present invention, by combining the above-mentioned multiple characterization methods, a comprehensive evaluation of the annealed product can be achieved. βThe electrical properties and crystal quality of Ga2O3 thin films provide reliable data support for subsequent device integration.

[0025] In one embodiment of the present invention, in step U10, it can be clearly seen from SEM and elemental surface scans that annealing successfully achieved the intercalation of nitrogen elements in the gallium oxide thin film.

[0026] In one embodiment of the present invention, in step U20, X-ray diffraction patterns show that the gallium oxide film still maintains excellent single-crystal properties after different annealing processes.

[0027] In one embodiment of the present invention, in step U30, the absorption rate of the gallium oxide film before and after annealing did not change significantly. From the bandgap fitting test results, the gallium oxide film after annealing still maintains the wide bandgap characteristics, with a bandgap width of 4.96~4.98 eV.

[0028] In one embodiment of the present invention, in step U40, the magnetic field strength of the Hall effect tester is -10 Tesla to 10 Tesla, and the Hall voltage is -100 mV to 100 mV. The Hall concentration is 10. 15 per cubic centimeter to 10 19 The Hall mobility is 16 to 18 cm³. 2 / V·s.

[0029] According to a fourth aspect of the present invention, a p-type is provided. β The p-type β-Ga2O3 single-crystal thin film can be prepared according to the method described in any embodiment of the first aspect. The thickness of the p-type β-Ga2O3 single-crystal thin film is 50 nanometers to 1 micrometer, and it has high hole concentration and mobility, while exhibiting excellent crystal quality and stability.

[0030] In some embodiments, the hole concentration of the p-type β-Ga2O3 single crystal thin film ranges from 0.5 × 10⁻⁶. 16 Up to 1×10 18 cm -3 Hole mobility ranges from 16 to 18 cm. 2 / V·s.

[0031] According to a fifth aspect of the present invention, a power device based on the aforementioned P-type β-Ga2O3 single-crystal thin film is also provided, including but not limited to field-effect transistors, diodes, or deep ultraviolet photodetectors. According to the present invention, since the power device employs the aforementioned P-type... β -Ga2O3 single crystal thin film, as the core material, exhibits excellent electrical performance and reliability, making it suitable for next-generation power electronics and optoelectronic applications.

[0032] In summary, the P-type provided in this application β The annealing process for Ga2O3 single-crystal thin films utilizes multi-stage atmosphere control and temperature gradient optimization techniques to precisely regulate the oxygen concentration in the gallium oxide film, significantly improving its properties. β The p-type conductivity and crystal quality of Ga2O3 single-crystal thin films lay a solid foundation for the practical application of next-generation power devices and deep ultraviolet photodetectors.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: I. The annealing process of this invention is simple and effective. Through the annealing process of this invention, non-metallic elements can be used to replace oxygen elements in the gallium oxide lattice without adding metal doping elements, thus achieving non-metallic element-doped p-type crystals. β -Ga2O3 single crystal thin film.

[0034] Second, the annealing process of the present invention improves the hole concentration by using a non-metallic element embedding method, optimizing the charge compensation mechanism, and reducing the self-compensation effect caused by donor defects, thereby overcoming the defect of low hole concentration caused by traditional divalent metal doping methods.

[0035] Third, this invention achieves precise control of oxygen concentration and lattice defects in gallium oxide thin film lattices even under high-temperature conditions through multi-stage pressure regulation and temperature gradient setting, effectively controlling p-type... β - The electrical properties of Ga2O3 single crystal thin films and the technical effect of ensuring high-quality thin film preparation. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the exemplary embodiments of the present invention and these drawings without any creative effort.

[0037] Figure 1 The XRD patterns of gallium oxide single crystal thin films before and after annealing are shown for different annealing times.

[0038] Figure 2 The images show the SEM and elemental surface scans of gallium oxide films after ammoniation on an alumina substrate.

[0039] Figure 3 The results show the absorption rate and band gap fitting of gallium oxide single crystal thin films before and after annealing at different annealing times.

[0040] Figure 4The Hall effect test results and statistical graphs of Hall concentration and Hall mobility of gallium oxide single crystal thin films before and after annealing are shown for different annealing times.

[0041] Figure 5 The XRD pattern and Hall effect test results of the gallium oxide thin film after high-temperature annealing are shown. Invention Details The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art will understand that many technical details have been provided in the various embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in this invention can be implemented even without these technical details and with various variations and modifications based on the following embodiments. Detailed Implementation

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Unless otherwise stated, the terms “include,” “including,” “have,” “contain,” etc., used in this document are open-ended terms, meaning that they include but are not limited to.

[0045] It should be understood that, for the numerical range in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed.

[0046] Preparation Example: p-type β Annealing treatment of Ga2O3 single crystal thin films Comparative example: Untreated β Preparation of Ga2O3 single crystal thin films β - The preparation of Ga2O3 single crystal thin films can be achieved using conventional thin film growth methods in the field, including physical vapor deposition methods such as magnetron sputtering, pulsed laser deposition and electron beam evaporation, chemical vapor deposition, liquid phase epitaxy, molecular beam epitaxy, etc., without any limitation.

[0047] In this comparative example, pulsed laser deposition was used to prepare... β -Ga2O3 single crystal thin film, the method includes the following steps: Step 1: Surface pretreatment of the substrate. A substrate is provided, and the substrate is cleaned sequentially with acetone and ethanol, followed by further ultrasonic cleaning of the substrate surface with deionized water to obtain a clean substrate surface. After drying, it is ready for use.

[0048] Step 2: Pre-treatment before pulsed laser deposition. The gallium oxide target, with a purity of 99% or higher, is pre-sputtered under vacuum conditions to remove surface impurities. The cleaned and dried substrate is then placed in the sputtering chamber of the pulsed laser deposition system and heated to a specified temperature of 600–900 °C. The oxygen partial pressure within the sputtering chamber is adjusted to 1–5 × 10⁻⁵. -1 Torr adjusts the distance between the target and the substrate to 70~75mm.

[0049] Step 3: Deposit gallium oxide thin films using pulsed laser deposition technology. Adjust the laser energy density to 1~12 mJ / mm². 2 Within the specified range, the deposition time was set to 15-60 min, and the deposition process was observed using a high-energy reflection electron diffractometer. After deposition, the cavity was cooled to obtain a gallium oxide thin film.

[0050] The substrate in step 1 can be aluminum oxide, strontium titanate, gallium oxide, silicon, silicon carbide, zinc oxide, gallium nitride, aluminum nitride, boron nitride, etc., and is not limited in any way. When the substrate is aluminum oxide, an aluminum oxide single crystal substrate with the orientation

[0001] is selected.

[0051] Examples 1-5: High-temperature annealing process β Preparation of Ga2O3 single crystal thin films Examples 1-5 provide a method for p-type β The annealing process for Ga2O3 single-crystal thin films involves placing the gallium oxide thin film in an annealing furnace and purging the furnace chamber with an inert gas or a mixture of an inert gas and an oxygen-free gas doped with a non-metallic element. The inert gas is selected from argon, helium, or nitrogen, and the doped non-metallic element is nitrogen, fluorine, or chlorine, preferably nitrogen. When using a mixture of an inert gas and an oxygen-free gas doped with a non-metallic element for furnace purging, the volume fraction of the oxygen-free gas containing the non-metallic element is 10% to 20%, and the volume fraction of the inert gas is 80% to 90%.

[0052] An annealing atmosphere gas is then introduced, which can be selected from ammonia, nitrogen fluoride, carbon trifluoride, carbon tetrafluoride, chlorine, carbon tetrachloride, etc., with ammonia being preferred.

[0053] The annealing program of the annealing furnace is set, specifying an annealing temperature of 400~800 °C, a heating rate of 3 to 8 °C per minute, and an annealing time of 1 to 3 hours. Optionally, the heating rate in the annealing furnace chamber is set in stages, first heating from room temperature to 450 °C at a heating rate of 3 to 5 °C per minute and holding for at least 20 minutes, then continuing to heat to 600~800 °C at a heating rate of 5 to 8 °C per minute and holding for 40 minutes to 3 hours. The annealing process under these conditions can maximize the activation of acceptor impurities while avoiding material damage caused by excessively high temperatures or excessively long times.

[0054] The gallium oxide thin film is annealed at a specified temperature, with the pressure inside the annealing furnace maintained between atmospheric pressure and 1.2 atmospheres to avoid damage to the film surface due to excessive pressure. Optionally, the pressure inside the annealing furnace is set in stages, with an initial pressure of 0.1 to 0.5 atmospheres, gradually increasing to 0.8 to 1.2 atmospheres during the heating process. By gradually adjusting the pressure inside the annealing furnace, the contact efficiency between atmosphere molecules and the film surface can be further optimized, thereby improving the annealing effect.

[0055] The gallium oxide film was then cooled to room temperature at a cooling rate of 4–10 °C / min while maintaining the annealing atmosphere, and the stability of the atmosphere within the chamber was continuously monitored during the cooling process. This resulted in a p-type gallium oxide film with non-metallic element substitution at oxygen sites in the gallium oxide lattice. β -Ga2O3 single crystal thin film.

[0056] Optionally, the gallium oxide film deposition and annealing steps can be repeated several times to obtain a gallium oxide film layer of the desired thickness.

[0057] Example 6: UV annealing process β Preparation of Ga2O3 single crystal thin films The annealing process in Example 6 is similar to that in Examples 1-5, except that ultraviolet (UV) light irradiation is used to anneal the gallium oxide thin film. The UV light has a wavelength of 200 nm to 300 nm, which effectively covers the bandgap energy of gallium oxide and has a high absorption rate. If the wavelength of the UV light is less than 200 nm, it is easily absorbed by the air, resulting in low energy utilization. If the wavelength of the UV light is greater than 300 nm, it cannot excite intrinsic charge carriers and can only serve a heating function.

[0058] The ultraviolet light irradiation power density is 20~200 mW / cm². 2At this point, a balance can be achieved between improving excitation efficiency and avoiding the risk of thin film damage. If the irradiation power density is too low, the excited electron-hole pairs will be insufficient, the driving force for defect repair or atomic diffusion will be weak, and the performance improvement will be limited. Conversely, if the irradiation density is too high, it will easily lead to local overheating, causing gallium oxide decomposition or thin film cracking.

[0059] During annealing, ultraviolet light directly excites valence band electron transitions in gallium oxide, generating a large number of electron-hole pairs. These carriers are highly reactive, and the high-energy photons also help break the weak Ga-O bonds in the thin film, thus creating active sites for the introduction of nitrogen atoms. Simultaneously, the energy of ultraviolet light facilitates local lattice adjustment and rearrangement near the doped region, promoting more stable nitrogen atom occupancy of oxygen sites and forming effective acceptor centers. Furthermore, the energy provided by ultraviolet light lowers the activation energy of the nitrogen substitution for oxygen process, allowing the reaction to proceed effectively at relatively lower temperatures, thereby further suppressing the formation of oxygen vacancies at high temperatures.

[0060] When using ultraviolet (UV) irradiation annealing, the irradiation time ranges from 10 minutes to 2 hours. The irradiation time needs to be optimized in conjunction with the power density; higher power results in a shorter required time. When the irradiation time is less than 10 minutes, the reaction is insufficient, the improvement in crystallinity is limited, and the defect concentration remains high. Conversely, when the irradiation time exceeds 2 hours, over-annealing may occur due to energy accumulation, leading to abnormal grain growth, increased surface oxidation, or the introduction of new defects, such as thermally stress-induced dislocations.

[0061] The advantage of UV annealing lies in the synergistic effect of low temperature. Compared with the traditional thermal annealing of 400-800°C in Examples 1-4, typically 600-800°C, the temperature range of UV annealing can be reduced to 300-600°C. It can provide thermal activation energy for atomic diffusion at a lower temperature, while avoiding the side effects of high temperature.

[0062] Example 7: Optimization through annealing process β Distribution of acceptor impurities in Ga2O3 thin films Example 7 investigated the effect of annealing process on optimization. β The effect of the main impurity distribution on the Ga2O3 thin film. Unlike the comparative example, Example 7 introduced divalent metal cations, such as magnesium or zinc ions, during the deposition of the gallium oxide thin film. In the prior art, divalent metal doping ions are often used to enhance the p-type characteristics of gallium oxide, but they are typically used to replace Ga in gallium oxide. 3+ The presence of lattice sites can lead to localized negative charges due to charge mismatch. These negative charges readily form charge compensation pairs with oxygen vacancies, which are common in gallium oxide, making it difficult for doped ions to ionize and release holes or electrons to form effective charge carriers. Furthermore, defect confinement may suppress activation.

[0063] In this context, the applicant of this invention overcame the bias of the prior art and, through numerous experiments, creatively proposed the annealing method of Example 7. By precisely controlling the doping concentration of metal cations and the nitrogen content in the annealing atmosphere, the ionization efficiency of acceptor impurities can be effectively improved and the hole trapping effect can be reduced, thereby achieving high-concentration and high-mobility p-type conductivity.

[0064] In the annealing method of Example 7, at the initial β During the deposition of Ga2O3 thin films, divalent metal cations (magnesium or zinc) are used as acceptor impurities, with a doping concentration of 10. 18 ~10 20 cm -3 10 preferred 19 ~10 20 cm -3 This is to ensure a sufficient amount of acceptor impurities.

[0065] During the annealing process, annealing is carried out in a mixed atmosphere. This allows for the synergistic control of oxygen partial pressure, nitrogen doping level, and lattice defects through multi-component synergistic regulation, while also considering the activation and ionization of divalent metal ions. In Example 7, the mixed atmosphere includes an atmosphere containing doped elements, preferably nitrogen or ammonia, and also includes an inert atmosphere for diluting and adjusting the nitrogen content, preferably argon or hydrogen.

[0066] During the annealing process, the nitrogen content in the annealing atmosphere is gradually increased through staged adjustments. This gradually activates magnesium ions to precisely control the occupancy rate of divalent metal ions, the oxygen vacancy concentration of the gallium oxide film, and lattice defects, while minimizing damage to the film structure. This achieves a synergistic effect of suppressing oxygen ionization and increasing nitrogen solubility, simultaneously enabling efficient p-type doping and oxygen vacancy control. Specifically, the nitrogen volume fraction can be set to 10% to 30% in the initial stage of annealing and gradually increased to 40% to 50% in the later stage; or the ammonia volume fraction can be set to 1% to 3% in the initial stage of annealing and gradually increased to 10% to 20% in the later stage.

[0067] The annealing process parameters for Examples 1-7 are summarized in Table 1 below: Table 1

[0068] Test Example: p-type before and after annealing β Performance testing of Ga2O3 single crystal thin films To evaluate the effect of annealing process on β The influence of Ga2O3 thin film crystal structure and photoelectric properties is addressed by the following technical means employed in the preparation examples and comparative examples. β The Ga2O3 thin film underwent the following performance tests: Surface morphology testing: The surface morphology of the thin film was observed by scanning electron microscopy (SEM). The scanning range of the scanning electron microscope (SEM) is from a few micrometers to tens of millimeters, and the resolution is less than 1 nanometer. Elemental embedding test: The thin film is subjected to elemental surface scanning by energy dispersive X-ray spectroscopy (EDS) to obtain elemental surface scanning spectra. The spatial resolution of energy dispersive X-ray spectroscopy (EDS) is generally better than 50 nm, and the energy resolution is generally between 125 eV and 133 eV. Crystal structure testing: The crystal structure of the thin film was analyzed using an X-ray diffractometer with a scanning angle range of 10 degrees to 70 degrees and a step size of 0.01 degrees to 0.05 degrees. Optical performance testing: The absorbance and bandgap fitting of gallium oxide thin films were tested using a UV-Vis-NIR spectrophotometer, with a test wavelength range of 200 to 1200 nm. Hall effect test: The hole concentration and mobility of the annealed film were measured using a Hall effect tester. The test temperature ranged from room temperature to 300 °C. The magnetic field strength of the Hall effect tester ranged from -10 Tesla to 10 Tesla, and the Hall voltage ranged from -100 mV to 100 mV.

[0069] The following description, in conjunction with the accompanying drawings, visually illustrates the effect of the annealing process of the present invention on the electrical properties and crystal quality.

[0070] See Figure 1 , Figure 1 The XRD patterns of gallium oxide single-crystal thin films from Examples 1-3 and the comparative example are shown. In the patterns, the three diffraction peaks (-201), (-402), and (-603) represent characteristic peaks of gallium oxide single crystals, and the * diffraction peak represents a characteristic peak of aluminum oxide single crystals. As can be seen from the figures, the gallium oxide thin film prepared by the pulsed laser deposition method in the comparative example exhibits good single-crystal characteristics, with a full width at half maximum (FWHM) of the diffraction peaks < 1°. Even after undergoing the annealing processes of Examples 1-3, the gallium oxide thin film still maintains excellent single-crystal characteristics.

[0071] See Figure 2 , Figure 2 The images show the SEM and elemental surface scans of the gallium oxide thin film after ammoniation on the alumina substrate in Example 1. Figure 2 Image a is the SEM image of the gallium oxide film after amination, which shows that a complete and uniform film has grown on the surface of the alumina substrate. β - Gallium oxide thin film layer, the thickness of the thin film layer is about 120 nm. Figure 2 b is the elemental surface scan spectrum of the gallium oxide thin film after ammonia treatment. It can be seen that nitrogen intercalation into the gallium oxide thin film was successfully achieved after annealing in an ammonia atmosphere.

[0072] See Figure 3 , Figure 3 The results are from absorbance and bandgap fitting tests performed on gallium oxide single-crystal thin films of Examples 1-3 and the comparative examples using a UV-Vis-NIR spectrophotometer. Figure 3 It can be seen that the absorptivity of the gallium oxide film did not change significantly before and after annealing. After 1 hour of annealing, the light absorption rate of the gallium oxide single crystal film can reach nearly 100%. From the bandgap fitting test results, the gallium oxide film still maintains the wide bandgap characteristics after annealing, with a bandgap width of 4.96~4.98 eV.

[0073] See Figure 4 , Figure 4 Hall effect tests were performed on the gallium oxide thin films of Examples 1-3. Figure 4 'a' represents the Hall effect test results. The horizontal axis in the graph represents magnetic field strength (Tesla), and the vertical axis represents Hall voltage (millivolts). From... Figure 4 As can be seen from Figure a, after the annealing process, the test data points of the gallium oxide thin film show a good linear relationship with the fitted line, indicating that the carrier concentration is uniform and the Hall effect is significant. That is, the gallium oxide single crystal thin film of the present invention maintains good p-type characteristics. Figure 4 b represents the Hall concentration and Hall mobility. It can be seen that after the annealing process, the Hall concentration of the gallium oxide film is 10. 15 per cubic centimeter to 10 19 Hall mobility can reach as high as 16 to 18 cm per cubic centimeter. 2 / V·s.

[0074] See Figure 5 , Figure 5 The XRD pattern and Hall effect tests were performed on the gallium oxide thin film of Example 4. Figure 5 a is the XRD pattern of the gallium oxide thin film in the comparative example and Example 4. It can be seen that the gallium oxide thin film after high-temperature annealing still exhibits good single-crystal characteristics, with a full width at half maximum (FWHM) of the diffraction peaks of <1°. Figure 5 b shows the Hall effect test results of the gallium oxide single crystal thin film after annealing. It can be seen that the test data points of the gallium oxide thin film and the fitted line show a good linear relationship, indicating that the carrier concentration is uniform and the Hall effect is significant. That is, the gallium oxide single crystal thin film in Example 4 maintains good p-type characteristics.

[0075] According to the present invention, by combining the above-mentioned multiple characterization methods, a comprehensive evaluation of the annealed product can be achieved. β The electrical properties and crystal quality of the Ga2O3 thin film provide reliable data support for subsequent device integration. The test results for the fabrication examples are summarized in Table 2 below: Table 2

[0076] Product Example: Based on p-type β -Power devices of Ga2O3 single crystal thin films As previously stated, the p-type obtained according to the annealing process of the present invention... β Ga₂O₃ single-crystal thin films, with thicknesses ranging from 100 to 500 nanometers, exhibit high hole concentration and mobility, with hole concentrations reaching up to 0.5 × 10⁻⁶. 16 Up to 1×10 18 cm -3 Hole mobility can reach 16 to 18 cm. 2 / V·s. Meanwhile, the p-type obtained after annealing... β -Ga2O3 single crystal thin films can still maintain wide bandgap characteristics, exhibiting excellent crystal quality and stability.

[0077] In this embodiment, a p-type based material was also prepared. β Power devices using Ga2O3 single-crystal thin films, including but not limited to field-effect transistors, diodes, or deep ultraviolet photodetectors. In the core material p-type... β Due to the excellent properties of Ga2O3 single crystal thin films, the power devices also exhibit excellent electrical performance and reliability, making them particularly suitable for next-generation power electronics and optoelectronic applications.

[0078] In summary, the p-type provided in this application β The annealing process for Ga2O3 single-crystal thin films utilizes multi-stage atmosphere control and temperature gradient optimization techniques to precisely regulate the oxygen concentration and lattice defects in gallium oxide films, significantly improving their yield. β The p-type conductivity and crystal quality of Ga2O3 single-crystal thin films lay a solid foundation for the practical application of next-generation power devices and deep ultraviolet photodetectors.

[0079] It should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure and are not intended to limit it. Although this disclosure has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this disclosure without departing from the spirit and scope of the technical solutions of this disclosure, and all such modifications and substitutions should be covered within the scope of the claims of this disclosure.

Claims

1. A method for p-type β -The annealing process for Ga2O3 single crystal thin films is characterized by, The process includes the following steps: placing a gallium oxide thin film into an annealing furnace, purging the furnace chamber with an inert gas or a mixture of an inert gas and an oxygen-free gas containing doped nonmetallic elements, then introducing an annealing atmosphere gas, annealing at a specified temperature, maintaining the annealing atmosphere, and cooling to room temperature to obtain a p-type gallium oxide crystal with nonmetallic elements replacing oxygen elements in the lattice. β -Ga2O3 single crystal thin film.

2. The p-type according to claim 1 β -The annealing process for Ga2O3 single crystal thin films is characterized by, The doped nonmetallic element is nitrogen, and the annealing atmosphere containing the doped nonmetallic element is an atmosphere containing ammonia.

3. The p-type according to claim 1 β -The annealing process for Ga2O3 single crystal thin films is characterized by, The mixture of inert gas and oxygen-free gas containing doped non-metallic elements has a volume fraction of 10% to 20% for oxygen-free gas containing doped non-metallic elements and a volume fraction of 80% to 90% for inert gas.

4. The p-type according to claim 1 β -The annealing process for Ga2O3 single crystal thin films is characterized by, The specified annealing temperature is 300~800 ℃, and the annealing time is 10 minutes~3 hours.

5. The p-type according to claim 1 β -The annealing process for Ga2O3 single crystal thin films is characterized by, The gallium oxide thin film was annealed using ultraviolet light irradiation, wherein the wavelength of the ultraviolet light was 250 nm to 400 nm and the irradiation power was 10 to 200 mW / cm². 2 .

6. The p-type according to claim 1 β -The annealing process for Ga2O3 single crystal thin films is characterized by, The gallium oxide thin film is doped with divalent metal cations as acceptor impurities, and the doping concentration of the divalent metal cation acceptor impurities is 10. 18 ~10 20 cm -3 .

7. The p-type according to claim 6 β -The annealing process for Ga2O3 single crystal thin films is characterized by, Annealing is carried out in a mixed atmosphere of nitrogen and argon. By adjusting the nitrogen content in the annealing atmosphere, the stepwise ionization and activation of the divalent metal cations are promoted. In the early stage of annealing, the volume fraction of nitrogen is set to 10% to 30%, and gradually increased to 40% to 50% in the later stage of annealing.

8. The p-type according to claim 6 β -The annealing process for Ga2O3 single crystal thin films is characterized by, Annealing is carried out in a mixed atmosphere of ammonia and argon. By adjusting the ammonia content in the annealing atmosphere, the stepwise ionization and activation of the divalent metal cations are promoted. In the early stage of annealing, the volume fraction of ammonia is set to 1% to 3%, and gradually increased to 10% to 20% in the later stage of annealing.

9. A p-type β -Ga2O3 single crystal thin film, characterized in that... The p-type according to any one of claims 1 to 8 β The p-type Ga2O3 single crystal thin film was prepared by an annealing process. β The thickness of the Ga2O3 single-crystal thin film ranges from 50 nanometers to 1 micrometer, and the hole concentration ranges from 0.5 × 10⁻⁶. 16 Up to 1×10 18 cm -3 Hole mobility ranges from 16 to 18 cm. 2 / V·s.

10. A p-type-based β -Power devices based on Ga2O3 single-crystal thin films, characterized in that, Using the p-type as described in claim 9 β Ga2O3 single crystal thin films can be used to prepare field-effect transistors, diodes, or deep ultraviolet light detectors.

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