Method for manufacturing single crystal film, and single crystal film

Abstract

To provide a method for manufacturing a single crystal film consisting of β-Ga2O3 using a THVPE method, using a technique capable of improving a film deposition rate without increasing an electrical resistance, and a single crystal film deposited as a film by the manufacturing method.SOLUTION: A method for manufacturing a single crystal film comprises a film deposition step of exposing a substrate 10 to mixed gas including GaCl3 gas used as a Ga raw material, O2 gas used as an O raw material, and In containing gas to grow a single crystal film 12 of β-(GaxAl1-x) 2O3 (0<x≤1) including In on the substrate 10. When x<1 in beta-(GaxAl1-x) 2O3 (0<x≤1), the mixed gas further includes AlCl3 gas as an Al raw material, and the ratio of the mass of In to the mass of Ga in the mixed gas is 0.1 mass% or more and 20 mass% or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a single crystal film and a single crystal film.

Background Art

[0002] Conventionally, a method for manufacturing a β-Ga2O3 single crystal film by the HVPE (Halide Vapor Phase Epitaxy) method is known (see Patent Document 1). In the method described in Patent Document 1, GaCl gas generated by reacting Ga and Cl and O2 gas are used as the Ga raw material and the O raw material of the β-Ga2O3 single crystal film, respectively.

[0003] Also, conventionally, a method for manufacturing a β-Ga2O3 single crystal film by the THVPE (Tri-Halide Vapor Phase Epitaxy) method is known (see Non-Patent Document 1). In the method described in Non-Patent Document 1, GaCl3 gas generated by vaporizing solid GaCl3 in a bubbling container and O2 gas are used as the Ga raw material and the O raw material of the β-Ga2O3 single crystal film, respectively.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] According to the method described in Patent Document 1 using the HVPE method, since the reaction between the raw material GaCl gas and O2 gas is very intense, the two easily react in the gas phase to form Ga2O3 powder, and this phenomenon often occurs where it is incorporated into the β-Ga2O3 single crystal film and significantly degrades the crystal quality of the film. Therefore, there is a problem that it is difficult to increase the supply amount of the raw material and it is difficult to increase the film formation rate.

[0007] On the other hand, according to the method described in Non-Patent Document 1 using the THVPE method, the reaction between GaCl3 gas and O2 gas is milder than the reaction between GaCl gas and O2 gas, and the generation of Ga2O3 powder is suppressed. Therefore, there is a possibility of increasing the film formation rate.

[0008] However, since solid GaCl3 for generating GaCl3 gas has very high hygroscopicity, it inevitably contains moisture, and due to the moisture contained in the solid GaCl3, the stainless steel bubbling container and piping contained in the apparatus are corroded. As a result, Fe, Cr, Ni, etc. contained in the stainless steel are transported together with the raw material gas and are mixed in large amounts into the β-Ga2O3 single crystal film. Since Fe, Cr, Ni become compensation acceptors in Ga2O3 and reduce the electron concentration, the electrical resistance of the β-Ga2O3 single crystal film increases.

[0009] An object of the present invention is to provide a method for manufacturing a single crystal film made of β-Ga2O3 using the THVPE method, which uses a technique capable of improving the film formation rate without increasing the electrical resistance, and a single crystal film formed by the manufacturing method.

Means for Solving the Problems

[0010] One aspect of the present invention provides the following method for manufacturing a single crystal film and a single crystal film in order to achieve the above object.

[0011] [1]Exposing a substrate to a mixed gas containing GaCl3 gas as a Ga source, O2 gas as an O source, and an In-containing gas to grow a single crystal film of β-(Ga x Al 1-x )2O3 (0 < x ≤ 1) on the substrate, and when x < 1 in the β-(Ga x Al 1-x )2O3 (0 < x ≤ 1), the mixed gas further contains AlCl3 gas as an Al source, and the ratio of the mass of In to the mass of Ga in the mixed gas is 0.1% by mass or more and 20% by mass or less. A method for manufacturing a single crystal film. [2] The method for manufacturing a single crystal film according to [1] above, wherein the In-containing gas contains InCl3 gas. [3] The method for manufacturing a single crystal film according to [1] or [2] above, which is carried out using a vapor phase growth apparatus made of a material that does not contain Fe, Cr, and Ni in the parts contacted by the chloride gas. [4] The method for manufacturing a single crystal film according to [1] or [2] above, wherein the ratio of the mass of In to the mass of Ga in the mixed gas is 1% by mass or more. [5] An epitaxial single crystal film of β-(Ga x Al 1-x )2O3 (0 < x ≤ 1), having an In concentration of 5 × 10 18 cm -3 or more and 1 × 10 20 cm -3 less than, and a Cl concentration of 1 × 10 14 cm -3 or more. A single crystal film. [6] The single crystal film according to [5] above, having an Fe concentration of 6 × 10 14 cm -3 or less, a Cr concentration of 2 × 10 14 cm -3 or less, and a Ni concentration of 2 × 10 15 cm -3 or less. [7] Formed on a substrate using a mixed gas containing GaCl3 gas as a Ga source, O2 gas as an O source, and an In-containing gas, and the β-(Ga x Al 1-x) When x < 1 in GaxAl1 - xO3 (0 < x ≤ 1), the single - crystal film according to [5] or [6] above, wherein the mixed gas further contains AlCl3 gas as an Al raw material. [8] β - (Ga x Al 1-x )2O3 (0 < x ≤ 1) is an epitaxial single - crystal film, which contains GaCl3 gas as a Ga raw material, O2 gas as an O raw material, and an In - containing gas, and is formed on a substrate using a mixed gas in which the ratio of the mass of In to the mass of Ga is 0.1 mass% or more and 20 mass% or less. When x < 1 in the β - (Ga x Al 1-x )2O3 (0 < x ≤ 1), the single - crystal film, wherein the mixed gas further contains AlCl3 gas as an Al raw material.

Advantages of the Invention

[0012] According to the present invention, there is provided a method for manufacturing a single - crystal film made of β - Ga2O3 using the THVPE method, which uses a technique capable of improving the film - forming rate without increasing the electrical resistance, and a single - crystal film formed by the manufacturing method.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] (Structure of the Crystal Stacked Structure) FIG. 1 is a vertical cross-sectional view of a crystal stacked structure 1 according to an embodiment of the present invention. The crystal stacked structure 1 has a substrate 10 and a single crystal film 12 formed on a main surface 11 of the substrate 10 by epitaxial crystal growth.

[0015] The single crystal film 12 is a film made of a single crystal of Ga2O3 having a β-type crystal structure, that is, β-Ga2O3. The single crystal film 12 may contain dopants such as Si and Sn.

[0016] The single crystal film 12 is formed by the THVPE method. The THVPE method is a crystal growth method developed from the HVPE method, and is different from the HVPE method in that GaCl3, which is a trihalide compound of Ga, is used instead of GaCl, which is a halide compound of Ga. The single crystal film 12 grows on the main surface 11 of the substrate 10 by exposing the substrate 10 to a mixed gas containing GaCl3 gas as a Ga source, O2 gas as an O source, and In-containing gas such as InCl3 gas.

[0017] In the film formation of the single crystal film 12, in order to increase the film formation rate by the THVPE method, the ratio of the mass of In to the mass of Ga in the above mixed gas is set to 0.1 mass% or more and 20 mass% or less. As a result, the single crystal film 12 contains 5×10 17 cm -3 or more and 1×10 20 cm -3 less than In. More preferably, the ratio of the mass of In to the mass of Ga in the above mixed gas is set to 1 mass% or more and 20 mass% or less. As a result, the single crystal film 12 contains 5×10 18 cm -3 or more and 1×10 20 cm -3 less than In. Since In is electrically neutral in Ga2O3 and does not act as a dopant, it hardly affects the electrical resistance of the single crystal film 12. Details of the addition of In to the single crystal film 12 will be described later.

[0018] In is sometimes added to reduce the band gap of Ga2O3 crystals in general. However, for this purpose, even if In less than 1×10 20 cm -3 is added, almost no effect can be obtained, so a higher concentration of In is added.

[0019] In addition, in the THVPE method, since GaCl3 gas containing Cl is used as the source gas, the single crystal film 12 contains Cl at a concentration of 1×10 14 cm -3 or higher.

[0020] Also, as will be described later, since the incorporation of Fe, Cr, and Ni, which act as compensating acceptors in Ga2O3, into the single crystal film 12 is suppressed, the single crystal film 12 is preferably formed using a vapor deposition apparatus made of a material that does not contain Fe, Cr, or Ni in the part where the chloride gases such as GaCl gas, GaCl3 gas, InCl gas, and InCl3 gas come into contact. Chlorides are highly hygroscopic and easily corrode the apparatus. If the corroded part contains Fe, Cr, or Ni, there is a risk that Fe, Cr, or Ni will flow out and be incorporated into the single crystal film 12. Note that not containing Fe, Cr, and Ni means not intentionally containing them, and also includes the case where an extremely small amount of any one or more of Fe, Cr, and Ni is inevitably contained. In that case, for example, the concentration of Fe in the single crystal film 12 is 6×10 14 cm -3 or less, the concentration of Cr is 2×10 14 cm -3 or less, and the concentration of Ni is 2×10 15 cm -3 or less.

[0021] The substrate 10 is a substrate that can be used as a base substrate for epitaxial growth of the single crystal film 12, such as a sapphire substrate or a β-Ga2O3 substrate made of a single crystal of β-Ga2O3. The substrate 10 may have a buffer layer on its surface. Also, the substrate 10 may contain a dopant.

[0022] (Structure of the vapor deposition apparatus) Hereinafter, an example of the structure of a vapor deposition apparatus used for growing the single crystal film 12 according to the present embodiment will be described.

[0023] FIG. 2 is a vertical cross-sectional view schematically showing the configuration of a vapor deposition apparatus 2 according to an embodiment of the present invention. The vapor deposition apparatus 2 is a vapor deposition apparatus for the THVPE (Tri-Halide Vapor Phase Epitaxy) method, and includes a reactor 20 having a first gas introduction port 21, a second gas introduction port 22, a third gas introduction port 23, and a fourth gas introduction port 24, a first chamber 25 and a second chamber 26 for generating a Ga source gas accommodated in the reactor 20, a substrate holder 27, and first heating means 29a and second heating means 29b installed around the reactor 20 for heating a predetermined region in the reactor 20. The first chamber 25 and the second chamber 26 communicate with each other.

[0024] The vapor deposition apparatus 2 is a two-step reaction type apparatus for the THVPE method that generates GaCl3 gas, which is a Ga source gas for the single crystal film 12, by chemical reactions in the first chamber 25 and the second chamber 26.

[0025] In the vapor deposition apparatus 2, in order to suppress the incorporation of Fe, Cr, and Ni, which serve as compensating acceptors in Ga2O3, into the single crystal film 12, components that may come into contact with the chloride gas are preferably made of a material that does not contain Fe, Cr, or Ni. For example, the reactor 20, the first chamber 25, the second chamber 26, the substrate holder 27, and the raw material container 28 installed in the first chamber 25 are made of quartz glass. On the other hand, the pipes connected to the reactor 20, the second chamber 26, and the first chamber 25, including the first gas introduction port 21, the second gas introduction port 22, and the third gas introduction port 23, do not come into contact with the chloride gas, so they do not necessarily have to be made of a material that does not contain Fe, Cr, or Ni.

[0026] The first gas introduction port 21 is used to introduce Cl2 gas into the first chamber 25 together with an inert gas such as N2 gas or Ar gas as a carrier gas.

[0027] The second gas introduction port 22 is used to introduce Cl2 gas into the second chamber 26 together with an inert gas such as N2 gas or Ar gas as a carrier gas.

[0028] The third gas introduction port 23 is used to introduce O2 gas into the reactor 20 together with an inert gas such as N2 gas or Ar gas as a carrier gas.

[0029] The fourth gas introduction port 24 is used to introduce an inert gas such as N2 gas or Ar gas as a carrier gas into the reactor 20. Also, when adding a dopant such as Si to the single crystal film 12, a dopant source gas such as SiCl4 is introduced into the reactor 20 from the fourth gas introduction port 24.

[0030] The substrate holder 27 is a component made of, for example, plate-shaped quartz glass. The raw material container 28 is a boat made of, for example, quartz glass, and in addition to the metallic Ga for generating GaCl3 gas, metallic In is accommodated. The raw material container 28 is installed in the first chamber.

[0031] The first heating means 29a and the second heating means 29b can heat, for example, the region where the first chamber 25 and the second chamber 26 in the reactor 20 are installed (hereinafter referred to as the Ga raw material generation region) and the region where the substrate holder 27 holding the substrate 10 is installed (hereinafter referred to as the crystal growth region). The first heating means 29a and the second heating means 29b are, for example, heating devices of a resistance heating type or a radiation heating type.

[0032] (Manufacture of Single Crystal Film) Hereinafter, an example of the method for manufacturing the single crystal film 12 according to the present embodiment will be described.

[0033] First, while maintaining the ambient temperature in the Ga raw material generation region of the reactor 20 at a predetermined temperature, for example, 500 to 900 °C, using the first heating means 29a, Cl2 gas is introduced into the first chamber 25 from the first gas introduction port 21 using a carrier gas, and the metallic Ga in the raw material container 28 is reacted with the Cl2 gas to generate GaCl gas. At this time, the introduced Cl2 gas reacts with the metallic In to generate InCl gas.

[0034] In addition, from the reaction of metallic Ga and Cl2 gas, GaCl2 gas, GaCl3 gas, and (GaCl3)2 gas, which are gallium chloride-based gases other than GaCl gas, are also generated. Among these gallium chloride-based gases, the partial pressure of GaCl gas is overwhelmingly high.

[0035] Next, Cl2 gas is introduced into the second chamber 26 from the second gas introduction port 22 using a carrier gas, and is reacted with the GaCl gas generated in the first chamber 25 and sent to the second chamber 26 to generate GaCl3 gas. At this time, the introduced Cl2 gas reacts with the InCl gas generated in the first chamber 25 and sent to the second chamber 26 to generate InCl3 gas.

[0036] Next, while maintaining the ambient temperature in the crystal growth region of the reactor 20 at a predetermined temperature, for example, 800 to 1100 °C, using the second heating means 29b, O2 gas is introduced into the reactor 20 from the third gas introduction port 23 using a carrier gas, and the introduced O2 gas is mixed with the GaCl3 gas and InCl3 gas generated in the second chamber 26 in the crystal growth region. Then, the substrate 10 is exposed to the mixed gas, and a single crystal film 12 is epitaxially grown on the main surface 11 of the substrate 10. Hereinafter, this step is referred to as a film formation step.

[0037] In the film formation step, for example, the supply partial pressure of GaCl3 gas is 1.0×10 ―3 ~4.0×10 -3 atm, and the value of the ratio (VI / III ratio) of the supply partial pressure of O2 gas to the supply partial pressure of GaCl3 gas is set to 1 to 500.

[0038] When adding dopants such as Si to the single crystal film 12, in the film formation process, a source gas of the additive element (for example, a chloride-based gas such as silicon tetrachloride (SiCl4)) is introduced from the fourth gas introduction port 24 into the crystal growth region of the reaction furnace 20.

[0039] In the film formation process, the single crystal film 12 incorporates In contained in the InCl3 gas while growing. Then, by the action of In as a catalyst, the film formation rate of the single crystal film 12 is improved. The addition amount of In to the single crystal film 12 can be controlled by the amount of metallic In disposed in the raw material container 28.

[0040] (Effect of In addition) Initially, in order to solve the problem of the THVPE method described in the above Non-Patent Document 1 in which Fe, Cr, and Ni are mixed into the β-Ga2O3 single crystal film due to corrosion of the apparatus when using solid GaCl3 for the production of GaCl3 gas, the present inventors constructed a THVPE apparatus formed of quartz glass and polytetrafluoroethylene that do not contain Fe, Cr, and Ni for the raw material container and flow path that come into contact with the GaCl3 gas, and attempted to form a β-Ga2O3 single crystal film.

[0041] As a result, although the incorporation of Fe, Cr, and Ni into the β-Ga2O3 single crystal film was suppressed, the film formation rate of the β-Ga2O3 single crystal film, which was 10 μm / h or more when using a conventional THVPE apparatus, greatly decreased to less than 0.1 μm / h, and only powder was generated in the gas phase even when the raw material supply amount was increased, and no improvement in the film formation rate was observed.

[0042] From this result, the present inventors conceived that metal impurities such as Fe, Cr, and Ni that were unintentionally incorporated when using a conventional THVPE apparatus functioned as some kind of catalyst and improved the film formation rate of the β-Ga2O3 single crystal film.

[0043] Therefore, the present inventors attempted to use an element that is electrically neutral in Ga2O3 and does not act as a compensating acceptor as a catalyst, and found that the growth rate of the β-Ga2O3 single crystal film was improved by using In.

[0044] Figure 3 is a graph showing the relationship between the amount of In added to the single crystal film 12 made of β-Ga2O3 and the film formation rate obtained by the demonstration experiment. In this experiment, a vapor phase growth apparatus 2 made of a material that does not contain Fe, Cr, or Ni in the part where chloride gases such as GaCl gas, GaCl3 gas, InCl gas, and InCl3 gas come into contact was used, and a single crystal film 12 was formed on a substrate 10 made of β-Ga2O3 by the above method. The following In addition amount (mass%) is the ratio of the mass of In to the mass of Ga in the mixed gas containing GaCl3 gas, O2 gas, and In-containing gas used for the film formation of the single crystal film 12.

[0045] First, when the single crystal film 12 was formed without adding In, the film formation rate was 2.6 μm / h. Next, when 1 mass% of In was added and the single crystal film 12 was formed, the film formation rate increased to 4.6 μm / h. Furthermore, when 10 mass% of In was added and the single crystal film 12 was formed, the film formation rate increased to 5.7 μm / h. The film formation conditions for these three types of single crystal films 12 (referred to as sample A) were the same except for the addition amount of In.

[0046] Next, when 10 mass% of In was added and the supply amounts of Cl gas and O2 gas were doubled to form a single crystal film 12 (referred to as sample B), the film formation rate increased to 8.7 μm / h. In addition, no obvious defects such as powder incorporation were observed in any of the above four types of single crystal films 12.

[0047] Figure 4 is a graph showing the impurity concentration and the secondary ion intensity of Ga in the single crystal film 12 to which 10 mass% of In was added, measured by secondary ion mass spectrometry (SIMS). "In: BG level", "Fe: BG level", "Cr: BG level", and "Ni: BG level" in the figure indicate the background levels (detection limits) of In, Fe, Cr, and Ni, respectively.

[0048] According to FIG. 4, In is contained in the single crystal film 12 at a concentration of approximately 5×10 19 cm -3 . Also, the concentrations of Fe, Cr, and Ni that act as compensating acceptors in the single crystal film 12 are 6×10 14 cm -3 or less, 2×10 14 cm -3 or less, and 2×10 15 cm -3 or less, respectively, and the mixing is sufficiently suppressed. The high concentration of each impurity in the vicinity of a depth of 0 μm is due to the influence of surface adsorbates.

[0049] The addition amount of In to the single crystal film 12 is preferably 0.1 mass% or more because if it is too small, it becomes difficult to control the addition amount. In this case, it is inferred from the measurement results of FIG. 4 that In is contained in the single crystal film 12 at a concentration of approximately 5×10 17 cm -3 or more.

[0050] Also, the measurement results of FIG. 3 show that if the addition amount of In is at least 1 mass% or more, the film formation rate of the single crystal film 12 is effectively improved. Therefore, the addition amount of In to the single crystal film 12 is more preferably 1 mass% or more. In this case, it is inferred from the measurement results of FIG. 4 that In is contained in the single crystal film 12 at a concentration of approximately 5×10 18 cm -3 or more.

[0051] Also, if the addition amount of In to the single crystal film 12 is too large, the change in the lattice constant of the single crystal film 12 becomes so large that there is a risk of crystal defects occurring. Therefore, it is preferably less than 20 mass%. In this case, it is inferred from the measurement results of FIG. 4 that In is contained in the single crystal film 12 at a concentration of approximately 1×10 20 cm -3 or less.

[0052] (Effect of the Embodiment) According to the embodiment of the present invention, in the formation of the single crystal film 12 made of β-Ga2O3 by the THVPE method, by growing the single crystal film 12 while adding a trace amount of In that is neutral in Ga2O3 and acts as a catalyst, the film formation rate can be improved without increasing the electrical resistance.

[0053] Furthermore, by using the vapor phase growth apparatus 2 in which parts that come into contact with chloride gases such as GaCl3 gas, which is the Ga raw material of the single crystal film 12, are made of a material that does not contain Fe, Cr, or Ni, the mixing of Fe, Cr, and Ni that increase the electrical resistance into the single crystal film 12 can be suppressed. As a result, a single crystal film 12 with a lower electrical resistance can be formed at a high film formation rate.

[0054] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention.

[0055] For example, GaCl3 gas and InCl3 gas for forming the single crystal film 12 may be generated by vaporizing solid GaCl3 and solid InCl3 in a bubbling container. In this case, since the vapor pressures of GaCl3 and InCl3 are significantly different, it is necessary to generate GaCl3 gas and InCl3 gas in separate bubbling containers, respectively.

[0056] Also, as the single crystal film 12, not only Ga2O3 but also a single crystal film of (Ga x Al 1-x )2O3 (0 < x < 1) in which a part of the Ga in Ga2O3 is replaced with Al can be manufactured. That is, as the single crystal film 12, a single crystal film of (Ga x Al 1-x )2O3 (0 < x ≤ 1) can be manufactured. A part of Ga is replaced with Al (Ga x Al 1-x)When manufacturing a single crystal film of 2O3 (0 < x < 1), in addition to GaCl3 gas, O2 gas, and In-containing gas, AlCl3 gas is used for the film formation of the single crystal film 12. Note that, unlike GaCl3 gas and InCl3 gas, AlCl3 gas needs to be generated in one step, for example, by vaporizing solid AlCl3 in a bubbling container, without going through the formation of monochloride. This is because AlCl reacts violently with quartz and erodes the part made of quartz glass in the reaction furnace 20.

[0057] Also, within the scope not departing from the gist of the invention, the components of the above-described embodiment can be arbitrarily combined. Also, the above-described embodiment does not limit the invention according to the claims. Also, it should be noted that not all combinations of the features described in the embodiment are essential means for solving the problems of the invention.

Explanation of Reference Numerals

[0058] 1... Crystal laminate structure, 10... Substrate, 11... Main surface, 12... Single crystal film, 2... Vapor phase growth apparatus, 20... Reaction furnace, 21... First gas introduction port, 22... Second gas introduction port, 23... Third gas introduction port, 24... Fourth gas introduction port, 25... First chamber, 26... Second chamber, 27... Substrate holder, 28... Raw material container, 29a... First heating means, 29b... Second heating means

Claims

1. GaCl as a Ga source ３ gas, O gas as an O source ２ Exposing a substrate to a mixed gas containing the gas and an In-containing gas to grow a single crystal film of β-(Ga ｘ Al １－ｘ )(0 < x ≤ 1) on the substrate, including a film forming step ２ O ３ (0 < x ≤ 1) on the substrate The above β-(Ga ｘ Al １－ｘ )) ２ O ３ When x < 1 in (0 < x ≤ 1), the mixed gas further contains AlCl ３ gas as an Al raw material, The ratio of the mass of In to the mass of Ga in the mixed gas is 0.1% by mass or more and 20% by mass or less, A method for manufacturing a single crystal film.

2. The In-containing gas is InCl ３ including the gas The method for manufacturing a single crystal film according to Claim 1.

3. The method is carried out using a vapor phase growth apparatus in which the parts contacted by the chloride gas are made of a material not containing Fe, Cr, and Ni, The method for manufacturing a single crystal film according to Claim 1 or 2.

4. The ratio of the mass of In to the mass of Ga in the mixed gas is 1% by mass or more, The method for manufacturing a single crystal film according to Claim 1 or 2.

5. β-(Ga ｘ Al １－ｘ )) ２ O ３ is an epitaxial single crystal film of (0 < x ≤ 1), The concentration of In is 5×10 １８ cm －３ or more and less than 1×10 ２０ cm －３ ​ The concentration of Cl is 1×10 １４ cm －３ or more. A single crystal film.

6. The concentration of Fe is 6×10 １４ cm －３ or less, The concentration of Cr is 2×10 １４ cm －３ or less, The concentration of Ni is 2×10 １５ cm －３ or less. The single crystal film according to Claim 5.

7. GaCl as a Ga source ３ gas, O as an O source ２ a film is formed on a substrate using a mixed gas containing the gas and an In-containing gas, Said β-(Ga ｘ Al １－ｘ )) ２ O ３ (0 < x ≤ 1), when x < 1, the mixed gas further contains AlCl ３ gas as an Al raw material, The single crystal film according to Claim 5 or 6.

8. β-(Ga ｘ Al １－ｘ ) ２ O ３ is an epitaxial single crystal film of (0 < x ≤ 1), GaCl as a Ga raw material ３ gas, O as an O raw material ２ gas, and an In-containing gas, and a mixed gas having a ratio of the mass of In to the mass of Ga of 0.1% by mass or more and 20% by mass or less is used to form a film on a substrate Said β-(Ga ｘ Al １－ｘ )) ２ O ３ (0 < x ≤ 1), when x < 1, the mixed gas further contains AlCl ３ gas as an Al raw material, A single crystal film.

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