An n-type gallium oxide thin film, a preparation method and application thereof

Abstract

The application provides an n-type gallium oxide thin film and a preparation method and application thereof. The preparation method comprises the following steps: providing an In-doped gallium oxide target material, a structural formula of the In-doped gallium oxide target material is (In x Ga 1‑x )2O3, 0 < x ≤ 0.05, wherein the concentration of In doping is ≤ 5% molar ratio; depositing the In-doped gallium oxide target material on a substrate to grow an In-doped gallium oxide thin film. The application further discloses the n-type gallium oxide thin film prepared according to the above method and application of the thin film in preparation of ultraviolet photoelectronic devices. The In doping scheme of the application is suitable for preparation of super-wide band gap low resistance gallium oxide thin films with different crystal phases, and has high conductivity on different types of hetero-substrates, which can effectively support research and development of different types of electronic devices. The application can effectively adjust the conductivity and optical properties of the thin film by adjusting the In doping concentration, and the preparation process is simple and has good universality.

Description

Technical Field

[0001] This application relates to the field of third-generation semiconductor materials technology, and in particular to an n-type gallium oxide thin film, its preparation method and application. Background Technology

[0002] Transparent conductive films, as functional materials possessing both optical transparency and conductivity, have become an indispensable component of semiconductor optoelectronic technology. With the continuous development of electronic devices such as deep ultraviolet light-emitting diodes (LEDs), solar cells, and sensors, the performance requirements for transparent conductive films are increasingly stringent, especially for ultra-wide bandgap transparent conductive films (bandgap width E...). g >4.0 eV), due to its excellent optoelectronic performance and stability, it exhibits unique advantages in fields such as high temperature, high power, and deep ultraviolet optoelectronic devices.

[0003] Currently, transparent conductive films mainly utilize oxide materials such as Sn-doped In₂O₃ (ITO), Al-doped ZnO (AZO), and CuAlO₂. However, the band gaps of these semiconductor materials are below 4.0 eV, making it difficult to meet the requirements for high transmittance in the ultraviolet region. Although reducing the film thickness can increase transmittance in the deep ultraviolet band, it also introduces the problem of decreased sheet resistance, making it difficult to simultaneously optimize both transmittance and sheet resistance. In recent years, gallium oxide, as an ultrawide bandgap semiconductor material, has a large band gap (4.8 eV~5.2 eV), excellent chemical and thermal stability, and is easy to n-type dopantize, making it a promising candidate for preparing deep ultraviolet transparent conductive materials and showing good application prospects in ultraviolet optoelectronic devices.

[0004] Ultrawide bandgap, low-resistivity n-type gallium oxide (GaO) thin films are mainly achieved by adding tetravalent dopants, including Si, Sn, and Hf. Corresponding doping schemes primarily show good results with epitaxial films grown on homoepitaxial GaO substrates. However, such films face the following challenges: due to the monoclinic crystal structure of thermally stable β-Ga2O3, there are limited substrate options that match its lattice. Consequently, the crystal quality and conductivity of homoepitaxial and heteroepitaxial films differ significantly, limiting the compatibility of current doping schemes with different types of substrates and electronic devices. Currently, the optimized conductivity of homoepitaxial β-Ga2O3 films is above 1000 S / cm, while the conductivity on heteroepitaxial substrates (such as sapphire and magnesium oxide) rapidly decreases to below 10 S / cm.

[0005] Therefore, to promote the development of gallium oxide in ultraviolet optoelectronic devices, it is urgent to explore n-type doping schemes for gallium oxide on heterogeneous substrates that combine ultraviolet transparency and high conductivity. How to explore novel doping methods to avoid the high dependence of traditional tetravalent doping schemes on gallium oxide crystal quality is a problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This application provides an n-type gallium oxide thin film, its preparation method, and its application, in order to at least solve the above-mentioned technical problems existing in the prior art.

[0007] According to a first aspect of this application, a method for preparing an n-type gallium oxide thin film is provided, comprising the following steps:

[0008] An In-doped gallium oxide target is provided, wherein the structural formula of the In-doped gallium oxide target is (In x Ga 1-x )2O3, 0<x≤0.05; in the In-doped gallium oxide target, the In doping concentration is ≤5% molar ratio;

[0009] The In-doped gallium oxide target is deposited on a substrate to grow an In-doped gallium oxide thin film, thus obtaining the n-type gallium oxide thin film.

[0010] According to one possible implementation of this application, at least the following beneficial effects are achieved:

[0011] 1. In this application, In is selected as the dopant element. 3+ with Ga 3+ The ionic radii are highly matched, and In has 4s spherical symmetric orbital characteristics, which effectively reduces the requirements for thin film crystal quality: (1) It is suitable for efficient doping activation of different heterogeneous substrates. 3+ Replacement Ga 3+ When entering the gallium oxide lattice, the atomic size difference is small, and the damage to the original lattice structure is weak. Even on different types of heterostructure substrates, it can reduce defects such as dislocations and vacancies caused by doping and achieve a high electron concentration; (2) Adaptation to polycrystalline gallium oxide: β-Ga2O3 (monoclinic system) and α-Ga2O3 (hexagonal system) have large differences in lattice structure, but In 3+ Its ionic radius and valence state characteristics allow it to be incorporated into both the monoclinic crystal system of the β phase and the hexagonal lattice of the α phase, without the need to adjust the doping elements for different crystal phases. In principle, it realizes that one doping scheme can adapt to multiple crystal phases, breaking through the crystal phase limitations of existing technologies.

[0012] 2. This application achieves performance balance through In doping concentration control. The core principle is based on the doping behavior and carrier transport characteristics of In in gallium oxide: (1) Controllable introduction of carrier concentration: Although In, as an impurity element, does not provide additional electrons as a donor element, its unique orbital characteristics can hybridize with O 2p orbitals, which is expected to change the deep energy level characteristics of oxygen defects and provide free electrons, significantly increasing the carrier concentration of the thin film, which can greatly reduce the thin film resistance and is suitable for low resistance requirements. (2) Stability guarantee of bandgap: In 3+ with Ga 3+ The valence state is consistent, and a high electron concentration can be achieved at a low doping concentration (0.1%), while having little impact on the band gap. The doped film is still much higher than the ultrawide band gap standard (Eg>4.0 eV), ensuring high transmittance in the deep ultraviolet band. (3) Optimization of carrier mobility: Thanks to the suppression of lattice distortion by In doping and the 4s spherical symmetric orbital characteristics that constitute the conduction band, the scattering probability of carriers in the lattice is reduced, and the mobility remains at a high level. Even on heterogeneous substrates, carriers can be transported efficiently, avoiding the problem of high carrier concentration but still high resistance due to low mobility, and finally achieving the synergy of ultrawide band gap and low resistivity.

[0013] 3. The process design of this application has high compatibility. The core principle lies in the characteristics of the precursor (i.e., In-doped gallium oxide target) and the universality of the deposition process: (1) The preparation of In-doped gallium oxide target does not require complex composition control technology, which can ensure the stability and repeatability of precursor preparation. (2) The physicochemical properties of In-doped gallium oxide target are stable, so that the target can be stably volatilized or sputtered under different temperature and pressure conditions of different deposition processes, and In element does not easily undergo oxidation state change during deposition (always in In). 3+ (The presence of the target material ensures the doping concentration and compositional uniformity of the final thin film, eliminating the need to adjust the target material formulation for specific processes and significantly reducing equipment investment and process adjustment costs.)

[0014] In one embodiment, the concentration of In doping specifically refers to the proportion of the number of In atoms to the total number of In+Ga atoms.

[0015] In one embodiment, the In-doped gallium oxide target is prepared by mixing, molding, and sintering indium oxide and gallium oxide.

[0016] Specifically, the molar ratio of indium oxide to gallium oxide is x:1-x, where 0 < x ≤ 0.05.

[0017] Specifically, the molding process is carried out using either cold isostatic pressing or unidirectional pressure molding; the molding pressure is 15 MPa to 30 MPa, and the holding time is 5 min to 15 min.

[0018] Specifically, the sintering temperature is 1400℃~1600℃, and the time is 4 h~8 h.

[0019] In one embodiment, the substrate is selected from sapphire (Al2O3) and Al with different crystal planes. 1-x Ga x N (0≤x≤1) is any one of epitaxial layer or substrate, or diamond.

[0020] Specifically, clean and smooth substrates with low lattice mismatch are preferred, such as a-plane sapphire, c-plane sapphire, (0001) oriented AlN epitaxial layer, and (100) oriented diamond. The size or shape of the substrate is not limited, depending on the substrate size compatible with the epitaxial equipment.

[0021] In one embodiment, the substrate is first cleaned before deposition, including: sequentially washing with acetone, ethanol, and water, and then drying with high-purity nitrogen.

[0022] In one embodiment, the deposition is selected from any one of pulsed laser deposition (PLD), magnetron sputtering deposition, electron beam evaporation deposition, molecular beam epitaxy (MBE), and chemical vapor deposition.

[0023] Specifically, since In-doped gallium oxide targets have stable physicochemical properties, different deposition processes can be selected. Some common deposition processes are listed above, but are not limited to these.

[0024] In a preferred embodiment, the deposition is performed using pulsed laser deposition at a temperature of 600°C to 700°C and an oxygen pressure of 0.01 mT to 20 mT.

[0025] In one embodiment, the thickness of the In-doped gallium oxide film is 10 nm to 600 nm.

[0026] According to a second aspect of this application, an n-type gallium oxide thin film prepared according to the above-described preparation method is provided.

[0027] According to a third aspect of this application, the application of the above-mentioned n-type gallium oxide thin film in the fabrication of ultraviolet optoelectronic devices is provided.

[0028] In one embodiment, the ultraviolet optoelectronic device includes, but is not limited to, deep ultraviolet light-emitting diodes, solar cells, and sensors.

[0029] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description

[0030] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of this application are illustrated in the drawings by way of example and not limitation, in which:

[0031] In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0032] Figure 1 The X-ray diffraction patterns of the n-type gallium oxide thin films of Examples 1, 3 and Comparative Example 1 of this application are shown.

[0033] Figure 2 The X-ray diffraction patterns of the n-type gallium oxide thin films of Examples 2, 4 and Comparative Example 2 of this application are shown.

[0034] Figure 3 The X-ray diffraction pattern of the n-type gallium oxide thin film of Example 5 of this application is shown;

[0035] Figure 4 The X-ray diffraction pattern of the n-type gallium oxide thin film of Example 6 of this application is shown;

[0036] Figure 5 The ultraviolet-visible transmission spectra of n-type gallium oxide thin films of Examples 1, 3 and Comparative Example 1 of this application are shown, along with their band gap comparison diagrams.

[0037] Figure 6 The UV-Vis transmission spectra of the n-type gallium oxide thin films of Examples 2, 4 and Comparative Example 2 of this application are shown, along with their band gap comparison diagrams. Detailed Implementation

[0038] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] Example 1

[0040] This embodiment prepared an n-type gallium oxide thin film, which is a β-Ga₂O₃ thin film with a 1% In doping concentration. Details are as follows:

[0041] (1) Select a c-plane sapphire substrate and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0042] (2) Indium oxide and gallium oxide powders with a purity greater than 99.99% were mixed uniformly at a molar ratio of 0.01:0.99, and formed by cold isostatic pressing at a pressure of 20 MPa for 10 min. The formed material was then sintered at 1500℃ for 6 h to obtain gallium oxide ceramic (In) with an In doping concentration of 1% atomic molar ratio. 0.01 Ga 0.99 )2O3 target material.

[0043] (3) A 1% In-doped gallium oxide thin film was deposited on the cleaned c-plane sapphire substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700℃, an oxygen pressure of 0.1 mT, and a film thickness of 240 nm.

[0044] Example 2

[0045] This embodiment prepared an n-type gallium oxide thin film, specifically an α-Ga₂O₃ thin film with a 1% In doping concentration. Details are as follows:

[0046] (1) Select a sapphire substrate on the a-side and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0047] (2) Indium oxide and gallium oxide powders with a purity greater than 99.99% were mixed uniformly at a molar ratio of 0.01:0.99, and formed by cold isostatic pressing at a pressure of 20 MPa for 10 min. The formed material was then sintered at 1500℃ for 6 h to obtain gallium oxide ceramic (In) with an In doping concentration of 1% atomic molar ratio. 0.01 Ga 0.99 )2O3 target material.

[0048] (3) A 1% In-doped gallium oxide thin film was deposited on the cleaned a-side sapphire substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700℃, an oxygen pressure of 0.1 mT, and a film thickness of 300 nm.

[0049] Example 3

[0050] This embodiment prepared an n-type gallium oxide thin film, which is a β-Ga₂O₃ thin film with a 5% In doping concentration. Details are as follows:

[0051] (1) Select a c-plane sapphire substrate and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0052] (2) Indium oxide and gallium oxide powders with a purity greater than 99.99% were mixed uniformly at a molar ratio of 0.05:0.95, and formed by cold isostatic pressing at a pressure of 20 MPa for 10 min. The formed material was then sintered at 1500℃ for 6 h to obtain gallium oxide ceramic (In) with an In doping concentration of 5% atomic molar ratio. 0.05 Ga 0.95 )2O3 target material.

[0053] (3) A 5% In-doped gallium oxide thin film was deposited on the cleaned c-plane sapphire substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700℃, an oxygen pressure of 0.1 mT, and a film thickness of 400 nm.

[0054] Example 4

[0055] This embodiment prepared an n-type gallium oxide thin film, specifically an α-Ga₂O₃ thin film with a 5% In doping concentration. Details are as follows:

[0056] (1) Select a sapphire substrate on the a-side and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0057] (2) Indium oxide and gallium oxide powders with a purity greater than 99.99% were mixed uniformly at a molar ratio of 0.05:0.95, and formed by cold isostatic pressing at a pressure of 20 MPa for 10 min. The formed material was then sintered at 1500℃ for 6 h to obtain gallium oxide ceramic (In) with an In doping concentration of 5% atomic molar ratio. 0.05 Ga 0.95 )2O3 target material.

[0058] (3) A 5% In-doped gallium oxide thin film was deposited on the cleaned a-side sapphire substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700℃, an oxygen pressure of 0.1 mT, and a film thickness of 400 nm.

[0059] Example 5

[0060] This embodiment prepared an n-type gallium oxide thin film, which is a β-Ga₂O₃ thin film with an In doping concentration of 0.1%. Details are as follows:

[0061] (1) An AlN buffer layer based on the (0001) orientation on a sapphire substrate was selected as the growth substrate and routine cleaning was performed, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0062] (2) Indium oxide and gallium oxide powders with a purity greater than 99.99% were mixed uniformly at a molar ratio of 0.001:0.999, and formed by cold isostatic pressing at a pressure of 20 MPa for 10 min. The formed material was then sintered at 1500℃ for 6 h to obtain gallium oxide ceramic (In) with an In doping concentration of 0.1% atomic molar ratio. 0.001 Ga 0.999 )2O3 target material.

[0063] (3) A 0.1% In-doped gallium oxide thin film was deposited on the cleaned substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700°C, an oxygen pressure of 0.1 mT, and a film thickness of 300 nm.

[0064] Example 6

[0065] This embodiment prepared an n-type gallium oxide thin film, which is a β-Ga₂O₃ thin film with an In doping concentration of 0.1%. Details are as follows:

[0066] (1) Select an unintentionally doped diamond substrate with (100) orientation and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol and deionized water, followed by drying with high-purity nitrogen.

[0067] (2) Indium oxide and gallium oxide powders with a purity greater than 99.99% were mixed uniformly at a molar ratio of 0.001:0.999, and formed by cold isostatic pressing at a pressure of 20 MPa for 10 min. The formed material was then sintered at 1500℃ for 6 h to obtain gallium oxide ceramic (In) with an In doping concentration of 0.1% atomic molar ratio. 0.001 Ga 0.999 )2O3 target material.

[0068] (3) A 0.1% In-doped gallium oxide thin film was deposited on the cleaned substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700°C, an oxygen pressure of 0.1 mT, and a film thickness of 100 nm.

[0069] Comparative Example 1

[0070] This comparative example prepared an n-type gallium oxide thin film. The difference from Example 1 is that this comparative example did not undergo In doping. Details are as follows:

[0071] (1) Select a c-plane sapphire substrate and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0072] (2) Gallium oxide powder with a purity greater than 99.99% was formed by cold isostatic pressing. The forming pressure was 20 MPa and the holding time was 10 min. The formed material was sintered at 1500℃ for 6 h to obtain undoped gallium oxide ceramic target material.

[0073] (3) An undoped gallium oxide thin film was deposited on the cleaned c-plane sapphire substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700°C, an oxygen pressure of 0.1 mT, and a film thickness of 190 nm.

[0074] Comparative Example 2

[0075] This comparative example prepared an n-type gallium oxide thin film. The difference from Example 2 is that this comparative example did not undergo In doping. Details are as follows:

[0076] (1) Select a sapphire substrate on the a-side and perform routine cleaning treatment, including sequential cleaning with acetone, ethanol, and deionized water, followed by drying with high-purity nitrogen.

[0077] (2) Gallium oxide powder with a purity greater than 99.99% was formed by cold isostatic pressing. The forming pressure was 20 MPa and the holding time was 10 min. The formed material was sintered at 1500℃ for 6 h to obtain undoped gallium oxide ceramic target material.

[0078] (3) An undoped gallium oxide thin film was deposited on the cleaned a-side sapphire substrate using pulsed laser deposition. The deposition conditions included a deposition temperature of 700°C, an oxygen pressure of 0.1 mT, and a film thickness of 200 nm.

[0079] Test case

[0080] 1. X-ray diffraction analysis was performed on the n-type gallium oxide thin films prepared in Examples 1-4 and Comparative Examples 1-2. The results are as follows: Figure 1 and Figure 2 As shown. Figure 1 The results show that the diffraction peaks of pure gallium oxide in Comparative Example 1 and 1% In-doped gallium oxide in Example 1 are single and sharp, corresponding only to β-Ga₂O₃. 01) The crystal plane indicates that low-concentration In doping did not change the β-phase structure of the thin film, and the crystal purity was high. The diffraction peak of the 5% In-doped gallium oxide in Example 3 was single, corresponding only to the β-Ga₂O₃ (…). 01) The crystal planes show a slight broadening of the peak shape, indicating that even high-concentration In doping did not alter the β-phase structure of the film. This demonstrates that In doping does not disrupt the crystal structure of β-Ga2O3, solving the problem of traditional tetravalent doping leading to phase disorder on heterogeneous substrates. This provides experimental support for the preparation of high-crystallinity β-Ga2O3 films on heterogeneous substrates. Figure 2 The results show that the diffraction peaks of pure gallium oxide in Comparative Example 2 and 1% In-doped gallium oxide in Example 2 are single and sharp, corresponding only to the (11) peaks of α-Ga₂O₃. 0) The crystal plane indicates that the low concentration of In doping did not change the α-phase structure of the thin film, and the crystal purity is high. The diffraction peak of the 5% In-doped gallium oxide in Example 4 is single, corresponding only to the (11) crystal plane of α-Ga₂O₃. 0) The crystal plane indicates that even high-concentration In doping did not alter the β-phase structure of the film. This demonstrates that In doping does not disrupt the crystal structure of α-Ga₂O₃, solving the problem of traditional tetravalent doping leading to phase disorder on heterogeneous substrates. This provides experimental support for the preparation of high-crystallinity α-Ga₂O₃ films on heterogeneous substrates.

[0081] 2. X-ray diffraction analysis was performed on the n-type gallium oxide films prepared in Examples 5 (AlN is an ultra-wide bandgap semiconductor heterostructure) and 6 (unintentionally doped diamond is a high thermal conductivity heterostructure, suitable for the heat dissipation requirements of high-power devices). The results are as follows: Figure 3 and Figure 4 As shown. Figure 3 The main characteristic peaks correspond to β-Ga2O3 ( 01) The crystal phase showed no diffraction signals from other crystal phases, and the peak shape did not show obvious broadening or splitting, proving that the thin film in Example 5 had stable crystal quality. It can be seen that there is a lattice mismatch between AlN and β-Ga2O3, but the directional growth of the thin film in Example 5 is still single-oriented, indicating that In doping can alleviate the crystal growth disorder caused by lattice mismatch and solve the problem of easy disorder of gallium oxide crystal phase on heterogeneous substrates in the prior art. Figure 4 The main characteristic peaks correspond to β-Ga2O3 ( 01) The crystal phase is free of impurity peaks and has a sharp peak shape, proving that even on a substrate with a greater difference in lattice structure, such as diamond, the thin film can still maintain a single β phase and directional growth characteristics. It can be seen that In doping can overcome the limitations of the significant differences in lattice constant and crystal structure between diamond and β-Ga2O3, making gallium oxide thin films suitable for high thermal conductivity diamond substrates and solving the pain point of heat dissipation difficulties in existing high-power gallium oxide devices.

[0082] In summary, the In-doped gallium oxide of this application can stably prepare single β-phase gallium oxide thin films on sapphire, AlN, and diamond heterostructures, thus being applicable to different types of heterostructures and overcoming the limitation of traditional tetravalent doping, which is only suitable for homostructures or specific heterostructures.

[0083] 3. The transmittance of the n-type gallium oxide thin films of Examples 1, 3, and Comparative Example 1 was measured using ultraviolet-visible spectrophotometry in the wavelength range of 200 nm to 800 nm, including the deep ultraviolet and visible light regions. The bandgap of the n-type gallium oxide thin films of Examples 1, 3, and Comparative Example 1 was measured using the Tauc plot method. The test results are as follows: Figure 5 As shown, the n-type gallium oxide films of Examples 1 (1% InGa2O3), 3 (5% InGa2O3), and Comparative Example 1 (pure Ga2O3) all exhibited average transmittances exceeding 90% in the deep ultraviolet region, with no significant decreasing trend. This indicates that In doping does not introduce a large amount of optical absorption impurities (such as elemental metals or defect states) into the β-Ga2O3 film, and does not damage the transparent and conductive core properties of the gallium oxide film, thus solving the problem that traditional high-concentration doping easily leads to a sharp drop in transmittance.

[0084] Bandgap testing showed that the Eg of the n-type gallium oxide film in Comparative Example 1 was 4.93 eV, while that in Example 1 was 4.92 eV. The difference between the two was minimal, indicating that the effect of low-concentration In doping on the bandgap is negligible, and the ultra-wide bandgap advantage of gallium oxide (Eg > 4.8 eV) can be stably maintained. The Eg of the n-type gallium oxide film in Example 3 decreased to 4.8 eV, but it is still much higher than that of traditional transparent conductive films (ITO's Eg is about 3.5 eV, and AZO's Eg is about 3.3 eV), still meeting the technical requirements of ultra-wide bandgap (Eg > 4.0 eV). It achieved a small-scale controllable adjustment of the bandgap, providing flexibility for adapting to different wavelength deep ultraviolet devices.

[0085] 4. Similarly, the transmittance of the n-type gallium oxide films of Examples 2, 4, and Comparative Example 2 was measured using ultraviolet-visible spectrophotometry in the wavelength range of 200 nm to 800 nm, including the deep ultraviolet and visible light regions. The bandgap of the n-type gallium oxide films of Examples 2, 4, and Comparative Example 2 was measured using the Tauc plot method. The test results are as follows: Figure 6 As shown, the n-type gallium oxide films of Examples 2 (1% InGa2O3), 4 (5% InGa2O3), and Comparative Example 2 (pure Ga2O3) all exhibited average transmittances exceeding 90% in the deep ultraviolet region, with no significant decreasing trend or abnormal absorption peaks. This indicates that In doping did not introduce a large number of optical defects (such as oxygen vacancy aggregation and impurity atom absorption centers) into the α-Ga2O3 film, and did not damage the transparent and conductive core properties of the gallium oxide film, thus solving the problem that traditional high-concentration doping easily leads to a sharp drop in transmittance.

[0086] Bandgap testing showed that the n-type gallium oxide film in Comparative Example 2 had an Eg of 5.2 eV, the widest bandgap among the three samples, consistent with the wide bandgap structural characteristics of α-phase gallium oxide itself. The Eg of the n-type gallium oxide film in Example 2 was 4.95 eV, while the Eg of the n-type gallium oxide film in Example 4 decreased to 4.8 eV, showing a slight decrease in Eg with increasing In doping concentration. However, the Eg of all samples was far higher than the threshold of ultra-wide bandgap (Eg > 4.0 eV), still meeting the requirements for wide bandgap stability in high-temperature and deep-ultraviolet devices. This is because In... 3+ The ionic radius of Ga 3+ The ionic radii differ, and In doping replaces Ga. 3+ This will slightly alter the lattice field environment of α-Ga2O3, causing a shift in the band edge, thereby enabling controllable adjustment of Eg.

[0087] 5. Test the electrical properties of the n-type gallium oxide thin films of Examples 1-6 and Comparative Examples 1-2. The resistivity, mobility, and carrier concentration of each n-type gallium oxide thin film were tested using the van der Bauer method. The test results are shown in Table 1. Table 1 shows that, compared with Comparative Example 1 (undoped, > range), Example 1 (1% doped, 0.13 Ω·cm), and Example 3 (5% doped, 78.8 Ω·cm): from undoped to 1% doped, the resistivity increases slightly but remains at a low level. This is because the resistivity in the undoped state is determined by the carriers provided by intrinsic defects, resulting in a low carrier concentration but high mobility; while with 1% In doping, a small number of free electrons are introduced, but In... 3+ with Ga 3+ Differences in ionic radii induce slight lattice vibrations, resulting in a slight decrease in carrier mobility and a slight increase in resistivity, while still maintaining low resistance. From 1% to 5% doping, the resistivity increases dramatically by 605 times, changing from low to high resistance. This is because while high In concentration significantly increases carrier concentration, a large amount of In... 3+ Replacement Ga 3+ This leads to increased β-phase lattice distortion, exponentially enhanced carrier scattering, a decrease in mobility far exceeding an increase in carrier concentration, and ultimately a surge in resistivity.

[0088] Comparing Comparative Example 2 (undoped, > range), Example 2 (1% doped, 0.67 Ω·cm), and Example 4 (5% doped, 0.12 Ω·cm): In the undoped case, the intrinsic carrier concentration of the α phase is extremely low, and the resistivity is > range (insulation); the low-concentration In doping in Example 2 provides a small number of carriers, reducing resistivity and achieving conductivity. Figure 2 It exhibits a single α phase (without distortion) and high mobility; the high-concentration In doping in Example 4 further increases the carrier concentration, and the α-phase hexagonal lattice supports the In... 3+The α-phase has a stronger capacity (no obvious lattice distortion), and the carrier mobility decreases only slightly, eventually reducing the resistivity to 0.12 Ω·cm. It is evident that the α-phase lattice structure (hexagonal) is more compatible with high-concentration In than the β-phase (monoclinic). At high concentrations, the former shows no obvious distortion (stable mobility), while the latter suffers distortion due to its high lattice rigidity (a sharp drop in mobility). This is the fundamental reason for the opposite resistivity responses of the two phases.

[0089] The β-phase samples on AlN and diamond substrates in Examples 5 and 6, with an In doping concentration of only 0.1%, had original resistivities of 0.03 Ω·cm and 0.11 Ω·cm, respectively, both maintaining low resistivity. Combined with XRD analysis of the single β-phase, it can be concluded that: the ultra-low concentration of In introduces only a small number of charge carriers, which is insufficient to cause lattice distortion (stable mobility); although the charge carrier concentration is low, the final resistivity remains low due to the high mobility; compared with the 5% doped sapphire substrate sample (78.8 Ω·cm), it proves that heterogeneous substrates need to balance the charge carrier concentration and mobility through ultra-low concentration + single crystal phase to avoid lattice distortion problems caused by high concentration.

[0090] Table 1

[0091]

[0092] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this application can be achieved, and this is not limited herein.

[0093] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0094] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing an n-type gallium oxide thin film, characterized in that, Includes the following steps: An In-doped gallium oxide target is provided, wherein the structural formula of the In-doped gallium oxide target is (In x Ga 1-x )2O3, 0.001≤x≤0.01; In the In-doped gallium oxide target, the In doping concentration is 0.1%~1% molar ratio; The In-doped gallium oxide target is deposited on a substrate to grow an In-doped gallium oxide thin film, thus obtaining the n-type gallium oxide thin film; the n-type gallium oxide thin film is a β-phase gallium oxide thin film or an α-phase gallium oxide thin film, and the resistivity of the n-type gallium oxide thin film is ≤0.67Ω·cm and the band gap is ≥4.8eV.

2. The preparation method according to claim 1, characterized in that, The In-doped gallium oxide target is prepared by mixing, molding, and sintering indium oxide and gallium oxide; The molar ratio of indium oxide to gallium oxide is x:1-x, where 0.001≤x≤0.

01.

3. The preparation method according to claim 2, characterized in that, The molding process is carried out using either cold isostatic pressing or unidirectional pressure molding; the molding pressure is 15 MPa to 30 MPa, and the holding time is 5 min to 15 min.

4. The preparation method according to claim 2, characterized in that, The sintering temperature is 1400℃~1600℃, and the time is 4 h~8 h.

5. The preparation method according to claim 1, characterized in that, The substrate is selected from sapphire and Al with different crystal planes. 1-x Ga x Any one of N epitaxial layer or substrate, and diamond; wherein, in the Al 1-x Ga x In the N-epitaxial layer or substrate, 0 ≤ x ≤ 1.

6. The preparation method according to claim 1, characterized in that, The deposition is selected from any one of pulsed laser deposition, magnetron sputtering deposition, electron beam evaporation deposition, molecular beam epitaxy, and chemical vapor deposition.

7. The preparation method according to claim 6, characterized in that, The deposition was performed using pulsed laser deposition at a temperature of 600℃~700℃ and an oxygen pressure of 0.01 mT~20 mT.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The thickness of the In-doped gallium oxide film is 10 nm to 600 nm.

9. An n-type gallium oxide thin film prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the n-type gallium oxide thin film of claim 9 in the fabrication of ultraviolet optoelectronic devices.

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