Method for manufacturing gallium oxide semiconductors

Abstract

To provide a method of producing a gallium oxide-based semiconductor having a larger bandgap than before.SOLUTION: A method of producing a gallium oxide-based semiconductor includes the steps of: forming a thin film containing θ-Al2O3 having a thickness of 1.5 nm or more and less than 13.0 nm by a physical vapor deposition method, on a substrate containing a β-Ga2O3 single crystal; and forming a thin film containing β-Ga2O3 by the physical vapor deposition method, on the thin film containing θ-Al2O3.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing gallium oxide-based semiconductors. [Background technology]

[0002] Currently, there is a demand for the development of energy-saving technologies, and the reduction of power loss in power devices is highly anticipated. Power devices are installed in all kinds of power converters, such as inverters used in hybrid and electric vehicles.

[0003] To realize low-loss power devices, new wide-bandgap semiconductor materials such as SiC and GaN, which are expected to enable power devices with even higher voltage resistance and lower loss than current silicon (Si), are attracting attention and are being actively researched and developed. Among these, gallium oxide is expected to provide even higher voltage resistance and lower loss, and other superior device characteristics when applied to power devices, due to its physical properties, such as an even larger bandgap, compared to SiC and GaN.

[0004] Gallium oxide semiconductors used in power devices were thought to be relatively difficult to manufacture, but in recent years several manufacturing methods have been proposed. For example, Patent Document 1 describes a method for manufacturing a gallium oxide semiconductor, in which a gallium oxide thin film is formed on a substrate containing a β-Ga2O3 single crystal by physical vapor deposition at a temperature of 400°C or lower, and then the thin film on the substrate is heated to a temperature of 700°C or higher.

[0005] Furthermore, research is progressing on the relationship between the properties and characteristics of gallium oxide. For example, Non-Patent Document 1 describes the simulation results regarding the relationship between the strain imparted to β-Ga2O3 and its band gap. Non-Patent Document 2 describes the crystal structure of β-Ga2O3, which is closely related to strain, and Non-Patent Document 3 describes the crystal structure of θ-Al2O3. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-50042 [Non-patent literature]

[0007] [Non-Patent Document 1] Junyu Lai,a et. al., “Flexible crystalline b-Ga2O3 solar-blind photodetectors”, Journal of Materials Chemistry C, 2020, 8, 14732-14739, 6th August 2020. [Non-Patent Document 2] Ahman et. al., Acta Cryst. C52, 1336(1996). [Non-Patent Document 3] E. Husson and Y. Repelin, Eur. J. solid State Inorg. Chem. 33, 1223(1996). [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] As mentioned above, gallium oxide-based semiconductor materials have a larger band gap compared to SiC and GaN. Therefore, gallium oxide-based semiconductors are expected to be used as next-generation power device materials, but it is desirable to further increase the band gap in order to further improve the voltage resistance.

[0009] This disclosure aims to provide a method for manufacturing gallium oxide-based semiconductors having a larger band gap than conventional semiconductors. [Means for solving the problem]

[0010] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> Forming a thin film containing θ-Al2O3 with a thickness of 1.5 nm or more and less than 13.0 nm on a substrate containing a β-Ga2O3 single crystal by physical vapor deposition, and Forming a thin film containing β-Ga2O3 on the thin film containing θ-Al2O3 by physical vapor deposition, including A method for manufacturing a gallium oxide-based semiconductor. <Aspect 2> The manufacturing method according to Aspect 1, wherein the thickness of the thin film containing θ-Al2O3 is 1.5 nm or more and 3.0 nm or less. <Aspect 3> The manufacturing method according to Aspect 1 or 2, wherein the thin film containing θ-Al2O3 is formed at 600 °C or more and 800 °C or less, and the thin film containing β-Ga2O3 is formed at 400 °C or more and 600 °C or less. <Aspect 4> The manufacturing method according to any one of Aspects 1 to 3, wherein the physical vapor deposition method is a vacuum evaporation method, a molecular beam epitaxy method, an ion plating method, an ion beam evaporation method, a conventional sputtering method, a magnetron sputtering method, an ion beam sputtering method, or an ECR sputtering method. <Aspect 5> The manufacturing method according to Aspect 4, wherein the molecular beam epitaxy method is a pulsed laser deposition method. [Effect of the Invention]

[0011] According to the present disclosure, by using a thin film containing θ-Al2O3 with a predetermined thickness, it is possible to suppress the generation of thermally unstable γ-Ga2O3 while imparting in-plane compressive strain to the thin film containing β-Ga2O3. And since the in-plane compressive strain modulates the electronic structure of β-Ga2O3 and contributes to the widening of the band gap, it is possible to provide a method for manufacturing a gallium oxide-based semiconductor having a larger band gap than before. Note that the in-plane compressive strain means compressive strain in the b-axis and c-axis directions in the crystal structure of β-Ga2O3. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram illustrating the preparation of a substrate containing a β-Ga2O3 single crystal. [Figure 2] Figure 2 is a schematic diagram illustrating a state in which a thin film containing θ-Al2O3 is formed on the surface of a substrate containing a β-Ga2O3 single crystal. [Figure 3] Figure 3 is a schematic diagram illustrating a state in which a thin film containing β-Ga2O3 is formed on the surface of a thin film containing θ-Al2O3. [Figure 4] Figure 4 is a graph showing how the relationship between energy loss and luminescence intensity changes with the thickness of the thin film containing θ-Al2O3. [Figure 5] Figure 5 is a graph showing the relationship between the thickness of a thin film containing θ-Al2O3 and the band gap of a thin film containing β-Ga2O3. [Figure 6] Figure 6 is a graph showing the XRD analysis results for the sample of Comparative Example 4 (thin film 20 containing θ-Al2O3 with a thickness of 13.0 nm). [Figure 7] Figure 7 is a graph showing the relationship between εa and εb in a thin film containing β-Ga2O3 when the thickness of the thin film containing θ-Al2O3 is 1.5 nm or more and less than 13.0 nm. [Modes for carrying out the invention]

[0013] The following describes embodiments of the method for manufacturing gallium oxide semiconductors according to this disclosure (hereinafter sometimes referred to as "the manufacturing method of this disclosure"). The manufacturing method of this disclosure is not limited to the following embodiments and can be implemented in various modifications within the scope of the spirit of this disclosure.

[0014] First, we will explain why the band gap of the gallium oxide-based semiconductor obtained by the manufacturing method of this disclosure becomes even larger than that of conventional semiconductors.

[0015] For some time, there has been research into further increasing the band gap of gallium oxide. For example, Non-Patent Document 1 describes simulation results suggesting that applying strain to β-Ga2O3 expands its band gap. However, Non-Patent Document 1 does not describe how to verify these simulation results, nor does it describe how to apply the strain.

[0016] Therefore, the Disclosing Parties investigated a method for manufacturing gallium oxide-based semiconductors having an even larger band gap than conventional semiconductors, and as a result, obtained the following findings, although not bound by theory.

[0017] When forming a thin film containing β-Ga2O3 on a substrate containing a β-Ga2O3 single crystal, it has been found that it is beneficial to pre-form a thin film containing θ-Al2O3 of a predetermined thickness on the surface of the substrate containing the β-Ga2O3 single crystal. This allows for the formation of a thin film containing β-Ga2O3 while suppressing the generation of thermally unstable γ-Ga2O3, and also enables the application of in-plane compressive strain to the thin film containing β-Ga2O3.

[0018] Both β-Ga2O3 and θ-Al2O3 have orthorhombic crystal structures, but as shown in Table 1, the lattice constants of θ-Al2O3 are several percent smaller than those of β-Ga2O3. The values ​​shown in Table 1 are based on those described in Non-Patent Document 2 for β-Ga2O3 and those described in Non-Patent Document 3 for θ-Al2O3.

[0019] [Table 1]

[0020] Because the lattice constants of β-Ga2O3 and θ-Al2O3 differ slightly, in-plane compressive strain can be imparted to a thin film containing β-Ga2O3 during its formation. It is believed that the thicker the thin film containing θ-Al2O3, the greater the mismatch in crystal structure between the θ-Al2O3 and β-Ga2O3 thin films, resulting in greater in-plane compressive strain. This increased in-plane compressive strain modulates the electronic structure of β-Ga2O3, expanding the band gap of the thin film. However, excessively large in-plane compressive strain makes it difficult to maintain the crystal structure of β-Ga2O3, leading to the formation of γ-Ga2O3. Since γ-Ga2O3 is thermally unstable, it is undesirable as a material for power devices. Therefore, to maintain the in-plane compressive strain within a predetermined range, the thickness of the thin film containing θ-Al2O3 is set to a predetermined range.

[0021] The above explanation will now be explained in order of the process, using diagrams. Figure 1 is a schematic diagram showing the state in which a substrate containing a β-Ga2O3 single crystal has been prepared. Figure 2 is a schematic diagram showing the state in which a thin film containing θ-Al2O3 has been formed on the surface of the substrate containing the β-Ga2O3 single crystal. Figure 3 is a schematic diagram showing the state in which a thin film containing β-Ga2O3 has been formed on the surface of the thin film containing θ-Al2O3.

[0022] As shown in Figure 2, a thin film 20 containing θ-Al2O3 is formed on the surface of a substrate 10 containing a β-Ga2O3 single crystal as shown in Figure 1. At this time, the thin film 20 containing θ-Al2O3 is made to a predetermined thickness. Then, a thin film 30 containing β-Ga2O3 is formed on the surface of the thin film 20 containing θ-Al2O3 that has the predetermined thickness. In the gallium oxide semiconductor 100 obtained in this way, in-plane compressive strain is applied to the thin film 30 containing β-Ga2O3. In addition, the generation of γ-Ga2O3 is suppressed during the formation of the thin film 30 containing β-Ga2O3. As a result, a gallium oxide semiconductor 100 with an even larger band gap than conventional semiconductors can be obtained.

[0023] The constituent elements of the manufacturing method of this disclosure, which have been completed based on the knowledge and other information described above, will now be explained.

[0024] 《Manufacturing method》 The manufacturing method disclosed herein includes a thin film formation step containing θ-Al2O3 and a thin film formation step containing β-Ga2O3. Each of these steps will be described below.

[0025] <Thin film formation process containing θ-Al2O3> The manufacturing method of this disclosure first involves forming a thin film containing θ-Al2O3 with a thickness of 1.5 nm or more and less than 13.0 nm on a substrate containing a β-Ga2O3 single crystal by physical vapor deposition.

[0026] The manufacturing method of this disclosure uses a substrate containing β-Ga2O3 single crystals. The surface index of the substrate is preferably (100), but is not limited thereto. It is preferable that the substrate contains as many β-Ga2O3 single crystals as possible. For example, the content of β-Ga2O3 single crystals relative to the entire substrate may be 80% by volume or more, 85% by volume or more, 90% by volume or more, or 95% by volume or more, or 100% by volume. The substrate containing β-Ga2O3 single crystals can be manufactured by any method. The content of β-Ga2O3 single crystals (by volume %) can be calculated from the peak intensity of the β-Ga2O3 single crystals by XRF analysis of the substrate.

[0027] A thin film containing θ-Al2O3 is formed by physical vapor deposition. There are no particular restrictions on the type of physical vapor deposition method, but examples include vacuum deposition, molecular beam deposition, ion plating, ion beam deposition, conventional sputtering, magnetron sputtering, ion beam sputtering, or ECR sputtering. Molecular beam deposition may be pulsed laser deposition (PLD).

[0028] If the thickness of the θ-Al2O3-containing thin film is 1.5 nm or more, 1.6 nm or more, 1.7 nm or more, or 1.8 nm or more, when a β-Ga2O3-containing thin film is formed on the θ-Al2O3-containing thin film by physical vapor deposition, in-plane compressive strain can be favorably applied to the β-Ga2O3-containing thin film, resulting in an expansion of the band gap. On the other hand, if the thickness of the θ-Al2O3-containing thin film is less than 13.0 nm, 12.0 nm or less, 10.0 nm or less, 5.0 nm or less, or 3.0 nm or less, when a β-Ga2O3-containing thin film is formed on the θ-Al2O3-containing thin film by physical vapor deposition, excessive in-plane compressive strain is not applied to the β-Ga2O3-containing thin film, and as a result, the formation of γ-Ga2O3 can be suppressed. The thickness of the θ-Al2O3-containing thin film can be measured by observing the cross-section of the θ-Al2O3-containing thin film by SEM or TEM.

[0029] It is preferable that the thin film containing θ-Al2O3 contains as few other substances as possible. The θ-Al2O3 content relative to the entire thin film may be 80% by volume or more, 85% by volume or more, 90% by volume or more, or 95% by volume or more, and may be 100% by volume. The θ-Al2O3 content (by volume) can be calculated from the peak intensity of θ-Al2O3 by XRF analysis of the thin film containing θ-Al2O3.

[0030] When employing pulsed laser deposition as a physical vapor deposition method, targets such as θ-Al2O3 sintered bodies and (0001)-plane α-Al2O3 single crystals can be used. From the viewpoint of stably obtaining the desired thin film, (0001)-plane α-Al2O3 single crystals are preferred. When such materials are used as targets, pulsed laser deposition may be performed in a gas atmosphere containing oxygen. Examples of oxygen-containing gas atmospheres include, but are not limited to, O2 or NO. The partial pressure of O2 in these atmospheres is, for example, 1 × 10⁻⁶ -3 Pa or higher, 5×10 -3 Pa or higher, or 10 × 10 -3It may be Pa or more and may be 500×10 -3 Pa or less, 100×10 -3 Pa or less, or 50×10 -3 Pa or less.

[0031] When applying the pulsed laser deposition method using a sintered body of θ-Al2O3 as the target, the laser fluence may be, for example, 0.01 J / cm 2 or more, 0.05 J / cm 2 or more, or 0.10 J / cm 2 or more, and may be 5.0 J / cm 2 or less, 1.0 J / cm 2 or less, or 0.50 J / cm 2 or less.

[0032] Also, when applying the pulsed laser deposition method using a sintered body of θ-Al2O3 as the target, the temperature during deposition may be, for example, 600 °C or more, 630 °C or more, or 650 °C or more, and may be 800 °C or less, 750 °C or less, or 700 °C or less.

[0033] When applying the pulsed laser deposition method, the thickness of the thin film containing θ-Al2O3 can be adjusted by the number of pulses.

[0034] 〈Thin film formation process containing β-Ga2O3〉 On the thin film containing θ-Al2O3 obtained as described above, a thin film containing β-Ga2O3 is formed by physical vapor deposition. There is no particular limitation on the type of physical vapor deposition method. For example, vacuum evaporation, molecular beam epitaxy, ion plating, ion beam evaporation, conventional sputtering, magnetron sputtering, ion beam sputtering, or ECR sputtering can be mentioned. The molecular beam epitaxy method may be the pulsed laser deposition (PLD) method.

[0035] When employing pulsed laser deposition as a physical vapor deposition method, sintered bodies of β-Ga2O3 and single crystals of (100)β-Ga2O3 can be used as targets. From the viewpoint of stably obtaining the desired thin film, single crystals of (100)β-Ga2O3 are preferred. When using these as targets, pulsed laser deposition may be performed in a gas atmosphere containing oxygen. Examples of gas atmospheres containing oxygen include, but are not limited to, O2 or NO. The partial pressure of O2 in these atmospheres may be, for example, 1 Pa or more, 5 Pa or more, or 10 Pa or more, and may be 500 Pa or less, 100 Pa or less, or 50 Pa or less.

[0036] When applying pulsed laser deposition using a sintered β-Ga2O3 target, the laser fluence is, for example, 0.01 J / cm². 2 More than 0.05J / cm 2 Above or equal to 0.10 J / cm² 2 The above is sufficient, and 5.0 J / cm 2 Below, 1.0J / cm 2 The following, or 0.50 J / cm² 2 The following is acceptable:

[0037] Furthermore, when using a sintered body of β-Ga2O3 as the target and applying pulsed laser deposition, the deposition temperature may be, for example, 400°C or higher, 430°C or higher, or 450°C or higher, and may be 600°C or lower, 550°C or lower, or 500°C or lower.

[0038] When applying pulsed laser deposition, the thickness of the thin film containing β-Ga2O3 can be adjusted by the number of pulses.

[0039] The thin film containing β-Ga2O3 obtained in this manner is subjected to strain. In-plane strain is 1-3% in the compressive direction, and perpendicular strain is 0.5-3.5% in the tensile direction. In-plane strain refers to strain in the b-axis and c-axis directions of the β-Ga2O3 crystal structure, while perpendicular strain refers to strain in directions perpendicular to the b-axis and c-axis of the β-Ga2O3 crystal structure.

[0040] There are no particular restrictions on the thickness of the thin film containing β-Ga2O3, but it should be appropriately determined to meet the characteristics required for gallium oxide semiconductors, such as high breakdown voltage and low loss. The thickness of the thin film containing β-Ga2O3 may be, for example, 1.0 nm or more, 2.0 nm or more, 3.0 nm or more, or 5.0 nm or more, and may be 100 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, 1 μm or less, 500.0 nm or less, 300.0 nm or less, 100.0 nm or less, 50.0 nm or less, 30.0 nm or less, 20.0 nm or less, or 10.0 nm or less. The thickness of the thin film containing β-Ga2O3 can be measured by observing the cross-section of the thin film containing β-Ga2O3 using SEM or TEM.

[0041] Preferably, a thin film containing β-Ga2O3 contains as few other substances as possible. The β-Ga2O3 content relative to the entire thin film containing β-Ga2O3 may be 80% by volume or more, 85% by volume or more, 90% by volume or more, or 95% by volume or more, and may be 100% by volume. The β-Ga2O3 content (by volume) can be calculated from the peak intensity of β-Ga2O3 by XRF analysis of the thin film containing β-Ga2O3. [Examples]

[0042] The manufacturing method of this disclosure will be described in more detail below with reference to examples and comparative examples. However, the manufacturing method of this disclosure is not limited to the conditions used in the following examples.

[0043] Sample preparation Samples for Examples 1-2 and Comparative Examples 1-4 were prepared according to the following procedure.

[0044] <Example 1> As shown in Figures 1-3, a thin film 20 containing θ-Al2O3 was formed on the surface of a substrate 10 containing a β-Ga2O3 single crystal, and then a thin film 30 containing β-Ga2O3 was formed to obtain a gallium oxide semiconductor 100.

[0045] The substrate 10 containing the β-Ga2O3 single crystal used was a β-Ga2O3 single crystal manufactured by Novel Crystal Technology Co., Ltd. The plane index of this single crystal was (100).

[0046] Both thin film 20 containing θ-Al2O3 and thin film 30 containing β-Ga2O3 were formed using pulsed laser deposition (PLD). The atmosphere during deposition was an oxygen radical atmosphere, and the partial pressure of O2 was 9.3 × 10⁻⁶. -3 Pa(7×10 -5 The torr value was, for example, 0.5 J / cm². 2 That was the case.

[0047] For the thin film 20 containing θ-Al2O3, a single crystal target of α-Al2O3 with a (0001) plane was used, and for the thin film 30 containing β-Ga2O3, a single crystal target of (100)β-Ga2O3 was used. The thin film 20 containing θ-Al2O3 was deposited at 700°C, and the thin film 30 containing β-Ga2O3 was deposited at 500°C.

[0048] By adjusting the pulse frequency, the thin film 20 containing θ-Al2O3 was deposited to a thickness of 1.53 nm, and the thin film 30 containing β-Ga2O3 was deposited to a thickness of approximately 10 nm.

[0049] <Example 2> The sample for Example 2 was prepared in the same manner as in Example 1, except that the thin film 20 containing θ-Al2O3 was deposited to a thickness of 2.52 nm.

[0050] <Comparative Example 1> The sample for Comparative Example 1 was prepared in the same manner as in Example 1, except that a thin film 20 containing θ-Al2O3 was not deposited beforehand.

[0051] <Comparative Example 2> A sample for Comparative Example 2 was prepared in the same manner as in Example 1, except that the thin film 20 containing θ-Al2O3 was deposited to a thickness of 0.86 nm.

[0052] <Comparative Example 3> A sample for Comparative Example 3 was prepared in the same manner as in Example 1, except that the thin film 20 containing θ-Al2O3 was deposited to a thickness of 1.25 nm.

[0053] <Comparative Example 4> A sample for Comparative Example 4 was prepared in the same manner as in Example 1, except that the thin film 20 containing θ-Al2O3 was deposited to a thickness of 13.0 nm.

[0054] Evaluation Method and Results The band gap of the thin film 30 containing β-Ga2O3 was measured for each sample in Examples 1-2 and Comparative Examples 1-4. The band gap was measured by reflection electron energy loss spectroscopy, and an example of the results is shown in Figure 4. Figure 4 is a graph showing that the relationship between energy loss and emission intensity changes with the thickness of the thin film 20 containing θ-Al2O3. In Figure 4, the value of the x-intercept represents the band gap. Table 2 is a summary of the band gaps of the thin film 30 containing β-Ga2O3 obtained in this way, organized by the thickness of the thin film 20 containing θ-Al2O3. Table 2 shows the band gaps of the thin film 30 containing β-Ga2O3 for Examples 1-2 and Comparative Examples 1-3. Based on Table 2, Figure 5 is a graph summarizing the relationship between the thickness of the thin film 20 containing θ-Al2O3 and the band gap of the thin film 30 containing β-Ga2O3.

[0055] Furthermore, XRD analysis was performed on each sample from Examples 1-2 and Comparative Examples 1-4. Figure 6 is a graph showing the XRD analysis results for the Comparative Example 4 sample (thickness of the θ-Al2O3-containing thin film 20 is 13.0 nm). Figure 6 also shows the XRD analysis results for samples with θ-Al2O3-containing thin film 20 thicknesses ranging from 0 to 3.0 nm. Note that a thickness of 0 nm for the θ-Al2O3-containing thin film 20 means that no θ-Al2O3-containing thin film 20 was formed.

[0056] In Figures 4 to 6 and Table 2, for the sake of simplicity, thin films containing θ-Al2O3 and thin films containing β-Ga2O3 are simply referred to as θ-Al2O3 and β-Ga2O3, respectively. Also, in Figure 6, "β400" means "(400) plane of β-Ga2O3", "γ400" means "(400) plane of γ-Ga2O3", and "β600" means "(600) plane of β-Ga2O3".

[0057] Furthermore, for reference, when the thickness of the thin film 20 containing θ-Al2O3 is 1.5 or more and less than 13.0 nm, ε a parε b We investigated this. Figure 7 is a graph showing the results of that investigation. Note that ε a* and ε b With respect to the strain applied to the thin film 30 containing β-Ga2O3, ε a* ε is a distortion perpendicular to the surface, b is the in-plane strain, where a positive value indicates tensile strain and a negative value indicates compressive strain. * The axis represents the inverse space vector, and its definition includes the cross product components of the b-axis and c-axis in real space, a * The axis directions correspond to the directions perpendicular to the b-axis and c-axis. The strain in the direction perpendicular to the plane was calculated from the XRD analysis results of thin film 30. ε b This was calculated from the analysis results of the reflective high-speed electron diffraction pattern of thin film 30.

[0058] [Table 2]

[0059] Figure 4 shows that when the thickness of the thin film 20 containing θ-Al2O3 exceeds a certain level, the band gap of the thin film 30 containing β-Ga2O3 tends to expand. Specifically, Table 2 and Figure 5 show that when the thickness of the thin film 20 containing θ-Al2O3 is 1.5 nm or more, the band gap of the thin film 30 containing β-Ga2O3 expands. The legend in Figure 4 indicates the thickness of θ-Al2O3.

[0060] Figure 6 shows that when the thin film 20 containing θ-Al2O3 has a thickness of 13.0 nm, a slight peak for γ-Ga2O3 is observed in the XRD analysis. From this, it can be understood that the thickness of the thin film 20 containing θ-Al2O3 should be less than 13.0 nm.

[0061] Furthermore, as shown in Figure 7, when the band gap of the thin film 30 containing β-Ga2O3 is expanded, ε a ε is a tensile strain greater than 0% and less than or equal to 3%. b We were able to confirm that the compression strain was between 0% and 3%.

[0062] Based on the above results, the effectiveness of the manufacturing method disclosed herein was confirmed. [Explanation of symbols]

[0063] 10 Substrate containing β-Ga2O3 single crystal 20 Thin film containing θ-Al2O3 30 Thin film containing β-Ga2O3 100 Gallium oxide semiconductors

Claims

1. β-Ga ２ O ３ On a substrate containing a single crystal, θ-Al is deposited by physical vapor deposition to a thickness of 1.5 nm or more and less than 13.0 nm. ２ O ３ Forming a thin film containing, The θ-Al ２ O ３ On a thin film containing β-Ga, by physical vapor deposition, ２ O ３ Forming a thin film containing including, A method for manufacturing gallium oxide semiconductors.

2. The thickness of the thin film containing the above-mentioned θ-Al ２ O ３ is 1.5 nm or more and 3.0 nm or less, and the manufacturing method according to claim 1.

3. The θ-Al ２ O ３ A thin film containing is formed at a temperature of 600°C or higher and 800°C or lower, and the β-Ga ２ O ３ The manufacturing method according to claim 1 or 2, wherein a thin film containing is formed at a temperature of 400°C or higher and 600°C or lower.

4. The manufacturing method according to claim 1 or 2, wherein the physical deposition method is vacuum deposition, molecular beam deposition, ion plating, ion beam deposition, conventional sputtering, magnetron sputtering, ion beam sputtering, or ECR sputtering.

5. The manufacturing method according to claim 4, wherein the molecular beam deposition method is a pulsed laser deposition method.

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