Manufacturing method for β-Ga2O3 single crystal film

Abstract

To provide a production method of a β-Ga2O3-based single crystal film that gives a high crystal growth rate and can suppress unintentional contamination of impurities acting as dopant, and to provide the β-Ga2O3-based single crystal film produced by the production method.SOLUTION: There is provided a production method of a β-Ga2O3-based single crystal film 12 composed of a β-Ga2O3 single crystal or a β-Ga2O3-based single crystal containing a β-Ga2O3 single crystal of which the part of Ga is replaced by one or both of Al and In. The production method of the β-Ga2O3-based single crystal film 12 comprises a step of producing a suboxide gas of A2O3 (A is Ga, Al, or In) without forming a substance containing impurities acting as dopant in the β-Ga2O3-based single crystal film 12 and a step of reacting the suboxide gas with O2 gas to subject the β-Ga2O3-based single crystal film 12 to epitaxial growth on a β-Ga2O3-based substrate 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a β-Ga2O3 single crystal Membrane It relates to a manufacturing method. [Background technology]

[0002] Conventionally, techniques for growing β-Ga2O3-based single crystal films by hydride vapor phase epitaxy (HVPE) or trihalide vapor phase epitaxy (THVPE) have been known (see, for example, Patent Document 1). In particular, the HVPE method has the excellent feature that it has a high crystal growth rate compared to other growth methods such as molecular beam epitaxy (MBE), and can form thick crystal films in a practical time at production sites. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6376600 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the HVPE and THVPE methods, Ga halide compounds (GaCl, GaCl3) are used as the raw material for the β-Ga2O3-based single crystal film, so Cl from the raw material becomes mixed into the β-Ga2O3-based single crystal film as an impurity. Cl acts as a shallow donor in β-Ga2O3-based semiconductors, so carriers (free electrons) are generated even when an undoped (not intentionally doped) β-Ga2O3-based single crystal film is formed. For example, when GaCl is used as the raw material, the concentration of Cl mixed into the β-Ga2O3-based single crystal film is 1 to 2 × 10 16 / cm 3 The concentration of carriers (free electrons) generated is also about the same.

[0005] For example, when a β-Ga2O3-based single crystal film is used in a power device, the breakdown voltage of the device is inversely proportional to the carrier concentration of the Ga2O3-based single crystal film. Therefore, in order to obtain a β-Ga2O3-based single crystal film that can be used to manufacture devices with higher breakdown voltages, it is important to prevent unintended incorporation of impurities that act as dopants, such as Cl, into the β-Ga2O3-based single crystal film.

[0006] Therefore, an object of the present invention is to provide a method for producing a β-Ga2O3-based single crystal film, which has a high crystal growth rate and is capable of suppressing unintended incorporation of impurities that act as dopants, and a β-Ga2O3-based single crystal film produced by said method. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention provides the following methods for producing a β-Ga2O3-based single crystal film [1] to [4], and the β-Ga2O3-based single crystal film [5] and [6].

[0008] [1] A method for producing a β-Ga2O3-based single crystal film made of a β-Ga2O3-based single crystal which is a β-Ga2O3 single crystal or a β-Ga2O3 single crystal in which a portion of Ga is substituted with either or both of Al and In, comprising the steps of: generating a suboxide gas of A2O3 (A is Ga, Al, or In) without generating any substance containing an impurity that acts as a dopant in the β-Ga2O3-based single crystal film; and reacting the suboxide gas with O2 gas to epitaxially grow the β-Ga2O3-based single crystal film on a substrate. [2] The method for producing a β-Ga2O3-based single crystal film according to [1] above, wherein in the step of generating the suboxide gas, Ga2O3 suboxide gas is generated by reacting Ga2O3 with metallic Ga, Al2O3 suboxide gas is generated by reacting Al2O3 with metallic Al, and In2O3 suboxide gas is generated by reacting In2O3 with metallic In. [3] The method for producing a β-Ga2O3-based single crystal film according to [1] or [2] above, wherein in the step of generating the suboxide gas, the suboxide gas is generated at an atmospheric temperature of 800° C. or higher. [4] The method for producing a β-Ga2O3-based single crystal film according to any one of [1] to [3] above, wherein in the step of epitaxially growing the β-Ga2O3-based single crystal film, the β-Ga2O3-based single crystal film is epitaxially grown at an atmospheric temperature of 800°C or higher. [5] It consists of a β-Ga2O3 single crystal or a β-Ga2O3 single crystal in which some Ga is replaced by Al, In, or both, and has a Cl concentration of 5×10 14 / cm 3 Below, the C content is 2×10 16 / cm 3 The following is a β-Ga2O3-based single crystal film. [6] The Sn content is 1×10 15 / cm 3 Below, the Si content is 5×10 15 / cm 3 The following is a list of compounds with an F content of 1×10 14 / cm 3 The β-Ga2O3-based single crystal film according to [5] above, which is as follows: Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for producing a β-Ga2O3-based single crystal film, which has a high crystal growth rate and is capable of suppressing unintended incorporation of impurities that act as dopants, and a β-Ga2O3-based single crystal film produced by the method. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a vertical cross-sectional view of a crystal layered structure according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical sectional view of a vapor phase growth apparatus according to an embodiment of the present invention. [Diagram 3]FIG. 3 is a graph showing the relationship between the partial pressures of Ga2O gas and GaO gas in Ga2O3 suboxide gas and temperature. [Figure 4] FIG. 4 is a graph showing the equilibrium constants in the formation reaction of Ga2O3 by each film formation method of the method according to the embodiment of the present invention, the HVPE method, and the THVPE method. [Diagram 5] FIG. 5 is a graph showing the measurement results of elemental analysis by SIMS of the crystal laminate structure according to the example of the present invention. [Figure 6] FIG. 6 is an observation image by an optical microscope of the surface morphology of a β-Ga2O3 single crystal film having a thickness of 3 μm.

DETAILED DESCRIPTION OF THE INVENTION

[0011] 〔Embodiment〕 (Configuration of Crystal Laminate Structure) FIG. 1 is a vertical cross-sectional view of a crystal laminate structure 1 according to an embodiment of the present invention. The crystal laminate structure 1 has a β-Ga2O3-based substrate 10 and a β-Ga2O3-based single crystal film 12 formed by epitaxial crystal growth on a main surface 11 of the β-Ga2O3-based substrate 10.

[0012] The β-Ga2O3-based substrate 10 is a substrate made of a β-Ga2O3-based single crystal. Here, the β-Ga2O3-based single crystal is a single crystal of β-Ga2O3 having a β-type crystal structure, or a single crystal of β-Ga2O3 in which part of Ga is substituted with one or both of Al and In, and (Ga x Al y In (1-x-y) )2O3 (0 <x ≦ 1, 0 ≦ y ≦ 1, 0 <x + y ≦ 1) has an ideal composition represented by. For example, (Ga x Al 1-x )2O3 (0 <x <1) in which part of Ga is substituted with Al has a larger bandgap than Ga2O3, and (Ga x In 1-x )2O3 (0 <x <1) in which part of Ga is substituted with In has a smaller bandgap than Ga2O3. Further, the β-Ga2O3-based substrate 10 may contain a dopant such as Sn or Si.

[0013] The plane orientation of the primary surface 11 of the β-Ga2O3-based substrate 10 is not particularly limited, and may be, for example, (001), (010), (−201), or (101).

[0014] The β-Ga2O3-based substrate 10 is formed by slicing a bulk crystal of a Ga2O3-based single crystal grown by a melt growth method such as the FZ (Floating Zone) method or the EFG (Edge Defined Film Fed Growth) method, and polishing the surface.

[0015] Instead of the β-Ga2O3-based substrate 10, a sapphire substrate or a silicon substrate may be used.

[0016] The β-Ga2O3-based single crystal film 12 is made of a β-Ga2O3-based single crystal, like the β-Ga2O3-based substrate 10. The β-Ga2O3-based single crystal film 12 is formed by an oxidation reaction of a suboxide of A2O3 (A is Ga, Al, or In), and since no substances containing impurities such as Cl and C that act as dopants in the β-Ga2O3-based single crystal film 12 are generated during the generation of the suboxide, the concentration of impurities that act as dopants is very low. Therefore, the β-Ga2O3-based single crystal film 12 has a very low carrier concentration and is excellent as a material for high-voltage devices.

[0017] For example, the Cl concentration of the β-Ga2O3-based single crystal film 12 is 5×10 14 / cm 3 In the following, the C content is 2×10 16 / cm 3 In the following, the Sn content is 1×10 15 / cm 3 In the following, the Si content is 5×10 15 / cm 3 In the following, the F content is 1×10 14 / cm 3 In the following, the H content is 2×10 17 / cm 3The following applies. Cl, C, Si, F, and H are all impurities that act as donors in the β-Ga2O3 single crystal film 12.

[0018] In the HVPE method and the THVPE method, since a halide compound of Ga (GaCl, GaCl3) is used as a raw material, it is very difficult to suppress the Cl concentration to 1×10 16 / cm 3 or less. Also, in the metalorganic chemical vapor deposition method (MOCVD method), since a metalorganic raw material (trimethylgallium (TMGa), triethylgallium (TEGa)) is used as a raw material, it is very difficult to suppress the C concentration to 3×10 16 / cm 3 or less.

[0019] Here, the suboxide of Ga2O3 is Ga2O or GaO in which the oxidation number of Ga is lower than that of Ga2O3. Also, the suboxide of Al2O3 is Al2O or AlO in which the oxidation number of Al is lower than that of Al2O3, and the suboxide of In2O3 is In2O or InO in which the oxidation number of In is lower than that of In2O3. When forming a β-Ga2O3 single crystal film as the β-Ga2O3 single crystal film 12, a suboxide of Ga2O3 is used as a raw material. When forming a β-(Ga x Al 1-x )2O3 (0 < x < 1) single crystal film as the β-Ga2O3 single crystal film 12, a suboxide of Ga2O3 and a suboxide of Al2O3 are used as raw materials. When forming a β-(Ga x In 1-x )2O3 (0 < x < 1) single crystal film as the β-Ga2O3 single crystal film 12, a suboxide of Ga2O3 and a suboxide of In2O3 are used as raw materials. When forming a β-(Ga x Al y In (1-x-y) )2O3 (0 < x ≦ 1, 0 ≦ y ≦ 1, 0 < x + y ≦ 1) single crystal film as the β-Ga2O3 single crystal film 12, a suboxide of Ga2O3, a suboxide of Al2O3, and a suboxide of In2O3 are used as raw materials.

[0020] In order to prevent impurity diffusion from the β-Ga2O3-based substrate 10, a buffer layer may be formed between the β-Ga2O3-based substrate 10 and the β-Ga2O3-based single crystal film 12.

[0021] The β-Ga2O3-based single crystal film 12 may contain intentionally added dopants such as Si, Sn, etc. In this case, as described above, the addition of unintentional dopants to the β-Ga2O3-based single crystal film 12 is suppressed, so that the concentration of the intentionally added dopant can be controlled with high precision.

[0022] (Structure of vapor phase growth apparatus) An example of the structure of a vapor phase growth apparatus used to grow a β-Ga2O3 single crystal film as the β-Ga2O3-based single crystal film 12 according to this embodiment will be described below.

[0023] 2 is a vertical cross-sectional view of a vapor phase growth apparatus 2 according to an embodiment of the present invention. The vapor phase growth apparatus 2 includes a reaction chamber 20 having a first gas inlet port 21, a second gas inlet port 22, a third gas inlet port 23, and an exhaust port 25, and a first heating means 27 and a second heating means 28 that are installed around the reaction chamber 20 and heat predetermined regions within the reaction chamber 20.

[0024] The reaction chamber 20 has a raw material reaction region R1 in which a reaction vessel 26 containing a raw material of Ga2O3 suboxide gas (hereinafter referred to as Ga2O3 suboxide gas) is placed and Ga2O3 suboxide gas is generated, and a crystal growth region R2 in which a β-Ga2O3-based substrate 10 is placed and a β-Ga2O3-based single crystal film 12 is grown. The reaction chamber 20 is made of, for example, quartz glass.

[0025] The reaction vessel 26 is made of, for example, quartz glass, and the raw materials of the Ga2O3 suboxide gas contained in the reaction vessel 26 are solid Ga2O3 (for example, single crystal bulk or polycrystalline powder) and liquid metallic Ga. The solid Ga2O3 and liquid metallic Ga are contained in the reaction vessel 26 in a state of contact with each other. Ga2O3 may be a single lump or a powder.

[0026] In addition, when forming a β-(Ga x Al 1-x )2O3 (0 < x < 1) single crystal film as the β-Ga2O3-based single crystal film 12, in addition to the raw material reaction region R1 that generates Ga2O3 suboxide gas, a vapor phase growth apparatus 2 equipped with a raw material reaction region R1 that generates a gas of a suboxide of Al2O3 (hereinafter referred to as Al2O3 suboxide gas) is used. In the raw material reaction region R1 that generates Al2O3 suboxide gas, a reaction vessel 26 containing Al2O3, which is a raw material of Al2O3 suboxide gas, and metallic Al is disposed.

[0027] Also, when forming a β-(Ga x In 1-x )2O3 (0 < x < 1) single crystal film as the β-Ga2O3-based single crystal film 12, in addition to the raw material reaction region R1 that generates Ga2O3 suboxide gas, a vapor phase growth apparatus 2 equipped with a raw material reaction region R1 that generates a gas of a suboxide of In2O3 (hereinafter referred to as In2O3 suboxide gas) is used. In the raw material reaction region R1 that generates In2O3 suboxide gas, a reaction vessel 26 containing In2O3, which is a raw material of In2O3 suboxide gas, and metallic In is disposed.

[0028] The first heating means 27 and the second heating means 28 can heat the raw material reaction region R1 and the crystal growth region R2 of the reaction chamber 20, respectively. The first heating means 27 and the second heating means 28 are, for example, heating devices of a resistance heating type or a radiation heating type.

[0029] The first gas inlet port 21 is a port for introducing a carrier gas for carrying the generated suboxide gas into the raw material reaction region R1 of the reaction chamber 20. The second gas inlet port 22 is a port for introducing O2 gas, which is an oxygen raw material gas, together with the carrier gas into the crystal growth region R2. The third gas inlet port 23 is a port for introducing the carrier gas and, if necessary, a raw material gas of a dopant that is intentionally added, such as SiCl4, into the crystal growth region R2 of the reaction chamber 20.

[0030] The carrier gases introduced from the first gas introduction port 21, the second gas introduction port 22, and the third gas introduction port 23 are inert gases such as N2 gas and Ar gas. If N is mixed into the β-Ga2O3-based single crystal film 12, it may act as an acceptor, but by adjusting conditions such as the partial pressure of the raw material supply and temperature, it is possible to prevent N from being mixed into the β-Ga2O3-based single crystal film 12. On the other hand, since Ar does not act as a dopant even if it is mixed into the β-Ga2O3-based single crystal film 12, it is preferable to use Ar gas as the carrier gas.

[0031] (Growth of β-Ga2O3 single crystal film) An example of a process for growing a β-Ga2O3 single crystal film as the β-Ga2O3-based single crystal film 12 according to this embodiment will be described below.

[0032] First, the raw material reaction region R1 of the reaction chamber 20 is heated using the first heating means 27, and the ambient temperature of the raw material reaction region R1 is kept at a predetermined temperature, for example, 800°C or higher. By setting the ambient temperature of the raw material reaction region R1 at 800°C or higher, the supply partial pressure of the Ga2O3 suboxide gas can be made approximately the same as the supply partial pressure of the Ga raw material gas in the HVPE method. The growth rate of the β-Ga2O3-based single crystal film 12 is proportional to the supply partial pressure of this Ga2O3 suboxide gas. In addition, the ambient temperature of the raw material reaction region R1 is set lower than the softening point of the reaction chamber 20 or the reaction vessel 26 (for example, about 1200°C if made of quartz glass).

[0033] Next, in the raw material reaction region R1, Ga2O3 and metal Ga in the reaction vessel 26 are reacted at the above-mentioned atmospheric temperature to generate Ga2O3 suboxide gas. Ga2O3 suboxide gas, Ga2O gas and GaO gas, are generated by the chemical reactions shown in the following formulas 1 and 2, respectively.

[0034]

number

[0035]

number

[0036] As shown in formulas 1 and 2, the Ga2O3 suboxide gas is generated without using raw materials containing elements such as Cl and C that act as dopants in the β-Ga2O3-based single crystal film 12. Therefore, no substance containing an element that acts as a dopant in the β-Ga2O3-based single crystal film 12 is generated during the generation of Ga2O gas.

[0037] Ga2O3 and metallic Ga are solid and liquid, respectively, due to their low vapor pressure, but the Ga2O and GaO produced by these reactions have a higher vapor pressure than Ga2O3 and metallic Ga, and become gaseous. Due to the difference in vapor pressure with the raw materials, high-purity Ga2O gas and GaO gas, i.e., Ga2O3 suboxide gas, can be obtained.

[0038] Figure 3 is a graph showing the relationship between the partial pressure and temperature of Ga2O gas and GaO gas in the suboxide gas generated by heating Ga2O3 and metallic Ga in contact with each other. As shown in Figure 3, the concentration of GaO gas in the Ga2O3 suboxide gas is negligibly low compared to the concentration of Ga2O gas. In other words, the Ga2O3 suboxide gas is composed almost entirely of Ga2O gas.

[0039] The partial pressures of Ga2O gas and GaO gas are determined almost solely by the ambient temperature in the raw material reaction region R1 if the mixing (contact) of Ga2O3 and metallic Ga is sufficient. Therefore, the supply amount of the Ga2O3 suboxide gas to the crystal growth region R2 is determined by the ambient temperature in the raw material reaction region R1 and the flow rate of the carrier gas that transports the Ga2O3 suboxide gas.

[0040] The generated Ga2O suboxide gas is transported to the crystal growth region R2 by a carrier gas such as Ar gas introduced from the first gas introduction port 21.

[0041] Note that when forming a β-Ga2O3-based single crystal film 12 as β-(Ga x Al 1-x )2O3 (0 < x < 1) single crystal film, in another raw material reaction region R1, for example, at an ambient temperature of 800 °C or higher and below the softening point of the reaction chamber 20 and the reaction vessel 26, Al2O3 and metallic Al in the reaction vessel 26 are reacted to generate Al2O3 suboxide gas. The Al2O gas and AlO gas, which are Al2O3 suboxide gases, are generated by the chemical reactions shown in the following formulas 3 and 4, respectively.

[0042]

Number

[0043]

Number

[0044] Also, when forming a β-Ga2O3-based single crystal film 12 as β-(Ga x In 1-x) When forming a (0 < x < 1) single crystal film of 2O3, in another raw material reaction region R1, for example, at a temperature of 800 °C or higher and an ambient temperature below the softening point of the reaction chamber 20 or the reaction vessel 26, In2O3 and metallic In in the reaction vessel 26 are reacted to generate In2O3 suboxide gas. The In2O gas and InO gas, which are In2O3 suboxide gases, are generated by the chemical reactions shown in the following equations 5 and 6 respectively.

[0045]

Number

[0046]

Number

[0047] The generated Al2O suboxide gas and In2O suboxide gas are also transported to the crystal growth region R2 by a carrier gas such as Ar gas introduced from the first gas introduction port 21, similar to the Ga2O suboxide gas.

[0048] Next, in the crystal growth region R2 of the reaction chamber 20 heated by the second heating means 28, the Ga2O suboxide gas generated in the raw material reaction region R1 is mixed with the O2 gas introduced from the second gas introduction port 22, and the β-Ga2O3-based substrate 10 is exposed to the mixed gas, and a β-Ga2O3-based single crystal film 12 is epitaxially grown on the main surface 11 of the β-Ga2O3-based substrate 10. The Ga2O3 constituting the β-Ga2O3-based single crystal film 12 is generated by the chemical reactions shown in the following equations 7 and 8.

[0049]

Number

[0050]

Number

[0051] The growth temperature of the β-Ga2O3 single crystal film 12 (the ambient temperature in the crystal growth region R2) is preferably 800 °C or higher. When it is lower than 800 °C, there is a possibility that metastable phases such as α-Ga2O3 and ε-Ga2O3 may be generated and single crystals may not be obtained. Also, the growth pressure of the β-Ga2O3 single crystal film 12 (the ambient pressure in the crystal growth region R2) is, for example, approximately 1 atm. Further, the growth temperature of the β-Ga2O3 single crystal film 12 is set lower than the lower of the melting point of Ga2O3 (about 1900 °C) and the softening point of the reaction chamber 20 (for example, about 1200 °C if it is made of quartz glass).

[0052] Figure 4 is a graph showing the equilibrium constants in the formation reactions of Ga2O3 by each of the film formation methods of the method according to the embodiment of the present invention, the HVPE method, and the THVPE method. The upper horizontal axis in Figure 4 is temperature (°C), the lower horizontal axis is 1000 / T (K -1 )(T is the absolute temperature), and the vertical axis is logK (K is the equilibrium constant). Figure 4 shows that Ga2O3 is more likely to be formed by the method according to the embodiment of the present invention than by the HVPE method and the THVPE method.

[0053] It has been confirmed by demonstration experiments that the growth rate of the β-Ga2O3 single crystal film 12 is approximately 1 to 10 μm / h depending on growth conditions such as the growth temperature. This growth rate is high compared to the growth rates of other crystal growth methods. For example, it is significantly higher compared to the growth rate of about several hundred nm / h of the MBE method. Also, it has been confirmed by demonstration experiments that there is a sufficient possibility that the growth rate will be equal to or higher than the growth rate of the HVPE method (several tens of μm / h) if the growth conditions are further adjusted.

[0054] When forming a β-(Ga x Al 1-x )2O3 (0 < x < 1) single crystal film as the β-Ga2O3 single crystal film 12, in addition to the Ga2O suboxide gas and the O2 gas, an Al2O suboxide gas is also introduced into the crystal growth region R2. The main chemical reaction for generating (Ga x Al 1-x )2O3 is shown in the following formula 9.

[0055] [Number]

[0056] As the β-Ga2O3-based single crystal film 12, when forming a β-(Ga x In 1-x )2O3 (0 < x < 1) single crystal film, in addition to the Ga2O suboxide gas and the O2 gas, the In2O suboxide gas is also introduced into the crystal growth region R2. The main chemical reaction for generating (Ga x In 1-x )2O3 is shown in the following formula 10.

[0057] [Number]

[0058] Note that after obtaining the β-Ga2O3-based single crystal film 12 through the above process, in order to reduce the electrical resistance in the thickness direction of the β-Ga2O3-based substrate 10, the β-Ga2O3-based substrate 10 may be thinned using means such as polishing. Further, the β-Ga2O3-based single crystal film 12 obtained through the above process may be separated from the β-Ga2O3-based substrate 10 using means such as polishing.

[0059] (Effect of the Embodiment) According to the above embodiment of the present invention, the raw materials of the β-Ga2O3-based single crystal film 12, Ga2O3 suboxide gas, Al2O3 suboxide gas, In2O3 suboxide gas, O2 gas, and the inert gas as the carrier gas, do not contain impurities such as Cl and C that function as dopants in the β-Ga2O3-based single crystal film 12, and Ga2O3, Al2O3, In2O3, metal Ga, metal Al, and metal In that are the raw materials of the suboxide gas do not contain impurities such as Cl and C that function as dopants in the β-Ga2O3-based single crystal film 12. Therefore, a substance containing an impurity that functions as a dopants in the β-Ga2O3-based single crystal film 12 is not generated with the generation of the suboxide gas. Therefore, the concentration of the impurity that functions as a dopants in the β-Ga2O3-based single crystal film 12 is very low, and by using the β-Ga2O3-based single crystal film 12 as a material for a device that requires a high withstand voltage, such as a Schottky barrier diode, a very high withstand voltage can be obtained.

[0060] Moreover, since the manufacturing method for the β-Ga2O3-based single crystal film 12 according to the embodiment of the present invention is excellent in the growth rate of the β-Ga2O3-based single crystal film 12, even if a certain thickness is required for the β-Ga2O3-based single crystal film 12 due to the characteristics of the device to which it is applied, the β-Ga2O3-based single crystal film 12 can be formed in a practical time at the production site. EXAMPLES

[0061] Fig. 5 is a graph showing the measurement results of elemental analysis by secondary ion mass spectrometry (SIMS) of the crystal laminated structure 1. In this example, a β-Ga2O3 single crystal substrate was used as the β-Ga2O3-based substrate 10, and a β-Ga2O3 single crystal film was used as the β-Ga2O3-based single crystal film 12. Fig. 5 shows the concentrations of impurity elements Cl, Sn, and Si that act as dopants in the β-Ga2O3-based single crystal film 12.

[0062] The horizontal axis of FIG. 5 is the depth (μm) from the surface of the β-Ga2O3 single crystal film (the surface of the crystalline laminated structure 1), and the vertical axis is the concentration of each element ( / cm 3) The dotted lines on the right side of the graph indicate the background (BG) level of each element concentration. The background level is the concentration of each element measured when nothing is placed inside the analyzer.

[0063] The depth ranges indicated by "β-Ga2O3 single crystal film" and "substrate" above the graph respectively indicate the measurement regions of the β-Ga2O3 single crystal film and the β-Ga2O3-based substrate 10 containing Sn as a dopant. Note that the rise in concentration of each element near the surface of the β-Ga2O3 single crystal film is due to the influence of surface adsorbates and does not indicate the concentration of each element inside.

[0064] According to Fig. 5, the Cl concentration in the β-Ga2O3 single crystal film is 5×10 14 / cm 3 This is consistent with the detection limit of the SIMS instrument, i.e., 5 × 10 14 / cm 3 It can be seen that the following is true.

[0065] In addition, the C concentration in the β-Ga2O3 single crystal film was 2×10 16 / cm 3 This is consistent with the detection limit of the SIMS instrument, i.e., 2 × 10 16 / cm 3 It can be seen that the following is true.

[0066] In addition, the Sn concentration in the β-Ga2O3 single crystal film was 1×10 15 / cm 3 This is consistent with the detection limit of the SIMS instrument, i.e., 1 × 10 15 / cm 3 It can be seen that the following is true.

[0067] In addition, the concentration of Si in the β-Ga2O3 single crystal film was 5×10 15 / cm 3 This is consistent with the detection limit of the SIMS instrument, i.e., 5 × 10 15 / cm 3It can be seen that the following is true.

[0068] In addition, the F concentration in the β-Ga2O3 single crystal film was 1×10 14 / cm 3 This is consistent with the detection limit of the SIMS instrument, i.e., 1 × 10 14 / cm 3 It can be seen that the following is true.

[0069] These extremely low concentrations of Cl, C, Sn, Si, and F are due to the fact that the Ga2O3 suboxide gas and O2 gas, which are the raw materials for the β-Ga2O3 single crystal film, Ga2O3 and metallic Ga, which are the raw materials for the Ga2O3 suboxide gas, and the inert gas, which is the carrier gas, do not contain Cl, C, Sn, Si, or F.

[0070] The reaction chamber 20 and reaction vessel 26 of the vapor phase growth apparatus 2 used for forming the β-Ga2O3 single crystal film are made of quartz glass (SiO2) and contain Si. However, based on the concentration of Si in the above-mentioned β-Ga2O3-based single crystal film 12, it is considered that there was almost no contamination of the β-Ga2O3 single crystal film with the Si contained in the reaction chamber 20 and reaction vessel 26.

[0071] In addition, the β-Ga2O3-based substrate 10, which is the base for epitaxial crystal growth of the β-Ga2O3 single crystal film, has a dopant concentration of about 5×10 18 / cm 3 However, based on the above-mentioned concentration of Sn in the β-Ga2O3 single crystal film, it is considered that the Sn contained in the β-Ga2O3-based substrate 10 was hardly mixed into the β-Ga2O3 single crystal film.

[0072] In addition, the H concentration of the β-Ga2O3 single crystal film was measured at a background level of 2×10 17 / cm 3However, since the raw materials for the β-Ga2O3 single crystal film, Ga2O3 suboxide gas and O2 gas, Ga2O3 and metallic Ga, which are the raw materials for the Ga2O3 suboxide gas, and the inert gas, which is the carrier gas, do not contain H, the H concentration in the β-Ga2O3 single crystal film is at the background level of 2 × 10 17 / cm 3 is estimated to be significantly lower than

[0073] Figure 6 is an optical microscope image of the surface morphology of a 3μm-thick β-Ga2O3 single crystal film. The image in Figure 6 shows the characteristic streaks on the surface of epitaxially grown crystals. This surface condition indicates that a film of comparable quality to that formed by the HVPE method has been obtained.

[0074] In this embodiment, the evaluation results of the β-Ga2O3 single crystal film are shown as the β-Ga2O3-based single crystal film 12. system unit The crystalline film β-(Ga x Al 1-x )2O3 single crystal film and β-(Ga x In 1-x Even when evaluating a β-Ga2O3 single crystal film, the unintentional inclusion of impurities that act as dopants is suppressed, as in the case of a β-Ga2O3 single crystal film, and similar evaluation results are obtained.

[0075] Although the embodiment and examples of the present invention have been described above, the present invention is not limited to the above embodiment and examples, and various modifications can be made without departing from the spirit and scope of the invention.

[0076] In addition, the above-described embodiments and examples do not limit the scope of the invention according to the claims. It should be noted that not all of the combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention. [Explanation of symbols]

[0077] 1...crystalline laminated structure, 10...β-Ga2O3-based substrate, 11...principal surface, 12...β-Ga2O3-based single crystal film, 2...vapor phase growth apparatus

Claims

1. β-Ga ２ O ３ or β-Ga in which a portion of Ga is replaced by one or both of Al and In. ２ O ３ β-Ga single crystal ２ O ３ β-Ga single crystal ２ O ３ A method for producing a silicon-based single crystal film, comprising the steps of: The β-Ga ２ O ３ A system without the formation of impurity-containing substances that act as dopants in the single crystal film ２ O ３ (A is Ga, Al, or In) The suboxide gas is O ２ The β-Ga is reacted with the gas to form a ２ O ３ epitaxially growing a nitride-based single crystal film; β-Ga ２ O ３ A method for producing a single crystal film based on the compound semiconductor material.

2. In the step of generating the suboxide gas, Ga ２ O ３ The suboxide gas is Ga ２ O ３ and metallic Ga are reacted to produce Al ２ O ３ In the case of generating suboxide gas of Al ２ O ３ is produced by reacting with metallic Al, and In ２ O ３ In the case of generating suboxide gas of ２ O ３ It is produced by reacting with metal In. The β-Ga according to claim 1 ２ O ３ A method for producing a single crystal film based on the compound semiconductor material.

3. In the step of generating the sub-oxide gas, the sub-oxide gas is generated under an atmospheric temperature of 800° C. or higher. The β-Ga according to claim 1 or 2 ２ O ３ A method for producing a single crystal film based on the compound semiconductor material.

4. The β-Ga ２ O ３ In the step of epitaxially growing a β-Ga-based single crystal film, ２ O ３ epitaxially growing a single crystal film of the system; The β-Ga according to any one of claims 1 to 3. ２ O ３ A method for producing a single crystal film based on the compound semiconductor material.

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