WO2024252544A1 - Crucible, method for producing beta-type digallium trioxide single crystal substrate using same, and beta-type digallium trioxide single crystal substrate - Google Patents

Abstract

A crucible for growing a beta-type digallium trioxide single crystal, wherein: the crucible thickness is 1-10mm, inclusive; the maximum inner diameter of the crucible is 100mm or more; the crucible composition is a stabilized zirconia containing yttrium oxide and/or calcium oxide; the surface on the inner-circumferential surface side of the crucible is coated with a sprayed film containing rhodium and/or platinum; the thickness of the sprayed film is 100-500μm, inclusive; and the stabilized zirconia at least contains 12.0-15.5 mass%, inclusive, of yttrium oxide or 10.2-11.4 mass%, inclusive, of calcium oxide.

Description

Crucible, method for producing beta-type digallium trioxide single crystal substrate using the crucible, and beta-type digallium trioxide single crystal substrate

This disclosure relates to a crucible, a method for producing a beta-type digallium trioxide single crystal substrate using the crucible, and a beta-type digallium trioxide single crystal substrate.

JP 2016-079080 A (Patent Document 1), JP 2017-193466 A (Patent Document 2), JP 2021-031367 A (Patent Document 3), JP 2021-031379 A (Patent Document 4), JP 2020-059633 A (Patent Document 5), and Hoshikawa et al., Journal of the Japanese Society for Crystal Growth, Vol. 44, No. 4(2017), 44-4-03 (Non-Patent Document 1) discloses a method for growing beta-type gallium trioxide single crystals (hereinafter also referred to as "beta-type Ga 2 O 3 single crystals") by a vertical boat method using a crucible made of a platinum-rhodium alloy (hereinafter also referred to as "Pt-Rh alloy") or a crucible or die made of a platinum-iridium alloy (hereinafter also referred to as " _{Pt-Ir alloy} "), or an EFG (Edge-defined Film-fed Growth) method, etc. JP 2000-129465 A (Patent Document 6) discloses a method for depositing platinum or a platinum-based alloy by thermal spraying on the surface of a refractory substrate such as ceramics.

JP 2016-079080 A JP 2017-193466 A JP 2021-031367 A JP 2021-031379 A JP 2020-059633 A JP 2000-129465 A

Hoshikawa et al., Journal of the Japanese Society for Crystal Growth, Vol. 44, No. 4 (2017), 44-4-03

The crucible according to the present disclosure is a crucible for growing beta-type gallium trioxide single crystals. The crucible has a thickness of 1 mm or more and 10 mm or less. The maximum inner diameter of the crucible is 100 mm or more. The composition of the crucible is stabilized zirconia containing both or either of yttrium oxide and calcium oxide. The surface on the inner peripheral side of the crucible is covered with a thermal spray film containing both or either of rhodium and platinum. The thickness of the thermal spray film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of the yttrium oxide, or 10.2 mass% or more and 11.4 mass% or less of the calcium oxide.

FIG. 1 is a schematic diagram illustrating a single crystal growth apparatus used in the manufacturing method of a beta type Ga ₂ O ₃ single crystal substrate according to this embodiment, and a main part of a crucible of a first embodiment used in the single crystal growth apparatus. FIG. 2 is an enlarged cross-sectional view of a main part of a crucible according to a second embodiment used in the single crystal growth apparatus of FIG. FIG. 3 is an enlarged cross-sectional view of a main portion of a crucible according to a third embodiment used in the single crystal growth apparatus of FIG. FIG. 4 is an enlarged cross-sectional view of a main portion of a crucible according to a fourth embodiment used in the single crystal growth apparatus of FIG. FIG. 5 is an enlarged cross-sectional view of a main part of a crucible according to a fifth embodiment used in the single crystal growth apparatus of FIG. FIG. 6 is a flow chart showing an example of a method for manufacturing a beta type Ga ₂ O ₃ single crystal substrate according to this embodiment. FIG. 7 is a schematic diagram illustrating a beta type Ga ₂ O ₃ single crystal substrate according to this embodiment. FIG. 8 is an explanatory diagram for explaining a Hall measurement sample prepared using the central portion of a beta type Ga ₂ O ₃ single crystal substrate according to this embodiment in order to measure the carrier concentration in the substrate.

[Problem to be solved by this disclosure]
As disclosed in Patent Documents 1 to 5 and Non-Patent Document 1, it is known that beta-type Ga ₂ O ₃ single crystals are grown and obtained using a crucible made of Pt-Rh alloy or Pt-Ir alloy. These crucibles made of Pt-Rh alloy, Pt-Ir alloy, etc. are expensive, and it is considered to reduce the thickness in order to reduce costs. However, the crucibles made of the above-mentioned Pt-Rh alloy, Pt-Ir alloy, etc. are easily deformed by thermal contraction, etc., and are cracked or chipped by the beta-type Ga ₂ O ₃ single crystals present in the crucible during crystal growth and cooling after crystal growth, so that it has been pointed out that the desired beta-type Ga ₂ O ₃ single crystals cannot be obtained with a high yield. In particular, the cracking of the crucible during crystal growth is fatal to obtaining beta-type Ga ₂ O ₃ single crystals. The method of depositing platinum or a platinum-based alloy by thermal spraying disclosed in Patent Document 6 is not intended to suppress cracking or chipping of the crucible, etc., and there is no suggestion of any action or effect of preventing the crucible from cracking during crystal growth. Therefore, a crucible using a thin film of a Pt-Rh alloy, Pt-Ir alloy, etc. that can at least suppress the occurrence of cracking and chipping during crystal growth and thereby produce beta-type _{Ga2O3 single} crystals with a high yield has not yet been obtained, and its development is eagerly awaited.

In view of the above, the present disclosure aims to provide a crucible that can suppress the occurrence of cracks, chips, etc. during crystal growth, a method for manufacturing a beta-type digallium trioxide single crystal substrate using the crucible, and a beta-type digallium trioxide single crystal substrate.

[Effects of the present disclosure]
According to the present disclosure, it is possible to provide a crucible capable of suppressing the occurrence of cracks, chips, and the like during crystal growth, a method for producing a beta-type digallium trioxide single crystal substrate using the crucible, and a beta-type digallium trioxide single crystal substrate.

[Overview of the embodiment]
The following is an outline of an embodiment of the present disclosure. The present inventors have made extensive studies to solve the above problems and have completed the present disclosure. First, the present inventors have focused on zirconia, which is a material with low thermal conductivity, stable against temperature changes, and difficult to deform, as a material for a crucible to which the vertical boat method is applied. In particular, the inner peripheral surface of the crucible made of zirconia is covered with a thin film containing both or either of rhodium and platinum, for example, a thin film made of a Pt- _Rh alloy containing Rh, which can handle the temperature (around 1800°C) required during crystal growth of a beta-type Ga 2 O ₃ single crystal. This has led to the idea of a crucible that can at least suppress the occurrence of cracks, chips, etc. during crystal growth. In addition, the present inventors have also found the thickness of the crucible and the thickness of the thin film that are appropriate for obtaining the single crystal with a high yield, and have arrived at the present disclosure.

Next, embodiments of the present disclosure will be listed and described.
[1] A crucible according to one embodiment of the present disclosure is a crucible for growing beta-type digallium trioxide single crystals. The crucible has a thickness of 1 mm or more and 10 mm or less. The maximum inner diameter of the crucible is 100 mm or more. The composition of the crucible is stabilized zirconia containing both or either of yttrium oxide and calcium oxide. The surface on the inner peripheral surface side of the crucible is covered with a sprayed film containing both or either of rhodium and platinum. The thickness of the sprayed film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of the yttrium oxide, or 10.2 mass% or more and 11.4 mass% or less of the calcium oxide. A crucible having such characteristics can suppress the occurrence of cracks, chips, etc. during crystal growth.

[2] In the crucible of [1] above, the sprayed film is preferably made of a platinum-rhodium alloy containing 10% by mass or more and 30% by mass or less of rhodium. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[3] In the crucible of [2] above, the sprayed film preferably has pores. The porosity, which is the volume ratio of the pores in the sprayed film, is preferably 30 volume % or more and 50 volume % or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[4] In the crucible of [2] above, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. The sprayed film preferably has pores. The porosity, which is the volume ratio of the pores in the sprayed film, is preferably 10 vol.% or more and less than 30 vol.%. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[5] In the crucible of [3] above, it is preferable that the surface roughness Rz of the surface is 300 μm or more and 500 μm or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[6] In the crucible of [1] above, the sprayed film preferably comprises a first film and a second film. The first film preferably covers the surface. The first film preferably comprises rhodium or a platinum-rhodium alloy mainly composed of rhodium. The second film preferably covers the first film. The second film preferably comprises platinum or a platinum-rhodium alloy mainly composed of platinum. The thickness of the sprayed film, including the first film and the second film, is preferably 100 μm or more and 500 μm or less. This makes it possible to suppress the incorporation of rhodium into the beta-type gallium trioxide single crystal.

[7] In the crucible of [6] above, it is preferable that both the first film and the second film have pores. It is preferable that the first film porosity, which is the volume ratio of the pores in the first film, and the second film porosity, which is the volume ratio of the pores in the second film, are both 30 volume % or more and 50 volume % or less. This can further suppress the occurrence of cracks, chips, etc. during crystal growth.

[8] In the crucible of [6] above, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. The first film and the second film both preferably have pores. The first film porosity, which is the volume ratio of the pores in the first film, and the second film porosity, which is the volume ratio of the pores in the second film, are both preferably 10 vol.% or more and less than 30 vol.%. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[9] In the crucible of [7] above, it is preferable that the surface roughness Rz of the surface is 300 μm or more and 500 μm or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[10] A method for producing a beta-type digallium trioxide single crystal substrate according to one embodiment of the present disclosure is a method for producing a beta-type digallium trioxide single crystal substrate using the crucible described in any one of [1] to [9] above. The method includes the steps of preparing the crucible, obtaining a beta-type digallium trioxide single crystal by a vertical boat method using the crucible, and processing the beta-type digallium trioxide single crystal to obtain a beta-type digallium trioxide single crystal substrate having a circular main surface. A method having such characteristics can produce a beta-type digallium trioxide single crystal substrate with good yield and product yield.

[11] A beta-type digallium trioxide single crystal substrate according to one embodiment of the present disclosure is a beta-type digallium trioxide single crystal substrate having a circular main surface. The diameter of the beta-type digallium trioxide single crystal substrate is 100 mm or more. The main surface is the (001) plane of the beta-type digallium trioxide single crystal. Or the main surface is a plane having an off angle of more than 0° and not more than 10° from the (001) plane of the beta-type digallium trioxide single crystal, and an off direction in the [010] direction of the beta-type digallium trioxide single crystal or a direction perpendicular to the [010] direction. The beta-type digallium trioxide single crystal substrate contains both or either one of rhodium and iridium. The rhodium concentration and the iridium concentration are both less than 3 ppm by mass in glow discharge mass spectrometry. A beta-type digallium trioxide single crystal substrate having such characteristics can be excellent in both electrical and optical properties.

[12] In the beta-type gallium trioxide single crystal substrate of [11] above, the transmittance for light having a wavelength of 400 nm or more and 430 nm or less is preferably 70% or more. The carrier concentration measured at 25° C. in the Hall measurement by the Van der Pauw method is preferably 1×10 ¹⁷ cm ⁻³ or more and 1.0×10 ¹⁹ cm ⁻³ or less. This makes it possible to achieve better electrical and optical properties.

[Details of the embodiment]
Hereinafter, one embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described in more detail, but the present disclosure is not limited thereto. In the following description, the drawings may be referred to, and the same or corresponding elements in this specification and the drawings will be given the same reference numerals, and the same description will not be repeated. Furthermore, in the drawings, the scale is appropriately adjusted to make each component easy to understand, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

In this specification, expressions in the format "A-B" refer to the upper and lower limits of a range (i.e., greater than or equal to A and less than or equal to B). If no unit is stated for A, and only a unit is stated for B, the units of A and B are the same. Furthermore, when compounds are expressed in chemical formulas in this specification, if the atomic ratio is not specifically limited, this includes all conventionally known atomic ratios, and should not necessarily be limited to only those within the stoichiometric range.

In this specification, "yield" means the ratio of the amount of beta-type gallium trioxide single crystal that can be grown to the desired thickness in the crucible without cracking or chipping in the crucible. In this specification, "product yield" means the ratio of the mass of the ingot of beta-type gallium trioxide single crystal grown in the crucible, which is evaluated as a good product for the substrate by the evaluation method described below, after first excluding the area where the crucible cracks or chips or the crystal cracks or chips during cooling, which would prevent the desired diameter from being obtained when processed into a beta-type gallium trioxide single crystal substrate. The larger the value of the "product yield" of the single crystal, the less likely it is that cracks, chips, etc. occurred in the crucible in which the single crystal was grown. Furthermore, in this specification, "main component" means a component whose content exceeds 95 mass% in a composition such as an alloy.

In this specification, the "maximum inner diameter" of a crucible refers to the inner diameter of the crucible at the position where the inner diameter of the ring that appears in a cross section perpendicular to the axial direction of the cylindrical crucible is maximum when compared along the axial direction of the crucible. In this disclosure, the crucible preferably has a structure that includes a cylindrical seed crystal storage section, an increased diameter section connected to the seed crystal storage section, and a straight body section connected to the increased diameter section, as described below. In a crucible of this type, the "maximum inner diameter" refers to the inner diameter of the straight body section.

In this specification, the "main surface" of a beta-type gallium trioxide single crystal substrate means both of the two circular faces of the beta-type gallium trioxide single crystal substrate. In the beta-type gallium trioxide single crystal substrate, if at least one of the two faces satisfies the scope of the claims of this disclosure, it falls within the technical scope of this disclosure. Furthermore, in this specification, the "face" used in the term "in-plane" means the "main surface." Furthermore, when the diameter of a beta-type gallium trioxide single crystal substrate is described as "100 mm," this means that the diameter is approximately 100 mm (approximately 95 to 105 mm), or 4 inches. When the diameter is described as "150 mm," this means that the diameter is approximately 150 mm (approximately 145 to 155 mm), or 6 inches. The diameter can be measured using a conventionally known outer diameter measuring device such as a caliper.

In the crystallographic descriptions in this specification, individual orientations are indicated with [ ], collective orientations with < >, individual faces with ( ), and collective faces with { }. In addition, when a crystallographic index is negative, it is usually indicated by placing a "- (bar)" above the number, but in this specification, a negative sign is placed before the number.

〔crucible〕
The crucible according to this embodiment is a crucible for growing beta-type digallium trioxide single crystals (beta-type _{Ga2O3 single} crystals). The crucible has a thickness of 1 mm or more and 10 mm or less. The maximum inner diameter of the crucible is 100 mm or more. The composition of the crucible is stabilized zirconia containing both or either of yttrium oxide and calcium oxide. The surface on the inner peripheral surface side of the crucible is covered with a sprayed film containing both or either of rhodium (Rh) and platinum (Pt). For example, the sprayed film is preferably made of a platinum-rhodium alloy (Pt-Rh alloy) containing 10 mass % or more and 30 mass % or less of Rh. The thickness of the sprayed film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least the yttrium oxide in an amount of 12.0% by mass to 15.5% by mass, or the calcium oxide in an amount of 10.2% by mass to 11.4% by mass. A crucible having such characteristics can suppress the occurrence of cracks, chips, and the like during crystal growth.

The crucible is a crucible for growing beta _- type _Ga2O3 single crystal as described above. The crucible is applied to a _single crystal growth apparatus, for example, as shown in FIG. 1, for the purpose of growing and obtaining a beta-type _Ga2O3 single crystal. The crucible according to this embodiment will be described in detail below by explaining the single crystal growth apparatus shown in FIG. 1. FIG. 1 is a schematic diagram illustrating the main parts of the single crystal growth apparatus used in the manufacturing method of _the beta-type _Ga2O3 single crystal substrate according to this embodiment, and the crucible of the first embodiment used in the single crystal growth apparatus.

As shown in FIG. 1, the single crystal growth apparatus 100 includes the crucible 5 described above, a crucible holder 6 that holds the crucible 5, and a heating device 7 that heats the crucible 5. The single crystal growth apparatus 100 may further include a sealed container 9 in which it is housed. There are no particular limitations on the dimensions and material of the sealed container 9, so long as it can house the single crystal growth apparatus 100 and the like and has the function of preventing impurities from entering from the outside.

The crucible 5 includes a cylindrical seed crystal accommodation portion 51, an increased diameter portion 52 connected to the seed crystal accommodation portion 51, and a straight body portion 53 connected to the increased diameter portion 52. The seed crystal accommodation portion 51 is cylindrical, has a hollow portion that opens to the side connected to the increased diameter portion 52 and has a bottom wall formed on the side opposite to the increased diameter portion 52. The seed crystal accommodation portion 51 can accommodate and hold the seed crystal 8a in the hollow portion. The increased diameter portion 52 has a truncated cone shape that expands upward in the axial direction of the crucible 5, and is connected to the seed crystal accommodation portion 51 on the small diameter side of the increased diameter portion 52. The straight body portion 53 has a hollow cylindrical shape and is connected to the large diameter side of the increased diameter portion 52. The diameter increasing portion 52 and the straight body portion 53 have a function of holding a block of gallium trioxide bulk material (specifically, _{polycrystalline Ga2O3} . Hereinafter, also referred to as " _{Ga2O3 bulk} material") therein. The diameter increasing portion 52 and the straight body portion 53 have a function of growing a beta-type _{Ga2O3 single} crystal as a crystal by solidifying the gallium trioxide melt as described later.

<Thickness and maximum inner diameter>
The crucible 5 has a thickness of 1 mm or more and 10 mm or less. More specifically, the side wall 5a of the seed crystal accommodation portion 51, the diameter increasing portion 52, and the straight body portion 53 of the crucible 5 all have a thickness of 1 mm or more and 10 mm or less. It is preferable that the side wall 5a of the seed crystal accommodation portion 51, the diameter increasing portion 52, and the straight body portion 53 of the crucible 5 all have a thickness of 5 mm or more and 10 mm or less. Furthermore, the maximum inner diameter of the crucible 5 is 100 mm or more. More specifically, it is preferable that the inner diameter of the straight body portion 53 of the crucible 5 is 100 mm or more. It is also preferable that the inner diameter of the straight body portion 53 of the crucible 5 is 150 mm or more. The upper limit of the maximum inner diameter of the crucible 5 is not particularly limited, but is, for example, 165 mm.

When the thickness of the crucible 5 is less than 1 mm, there is a possibility that cracking and chipping of the crucible 5 during crystal growth may not be sufficiently suppressed. There is also a possibility that the crucible 5 may be deformed during crystal growth. When the thickness of the crucible 5 exceeds 10 mm, there is a possibility that the adverse effect of the increase in the cost of the crucible 5 may outweigh the effect of cost reduction and the like obtained by suppressing cracking and chipping of the crucible 5 during crystal growth. By making the maximum inner diameter of the crucible 5 100 mm or more, it is possible to suppress cracking and chipping of the crucible 5 when manufacturing a large-diameter _beta -type _Ga2O3 single crystal substrate with a diameter of 4 inches or 6 inches.

<Crucible composition: stabilized zirconia>
The composition of the crucible 5 is stabilized zirconia (hereinafter also referred to as "stabilized ZrO ₂ ") containing both or either of yttrium oxide (yttria: Y ₂ O ₃ ) and calcium oxide (calcia: CaO). The composition of the crucible 5 is preferably stabilized ZrO ₂ containing either Y ₂ O ₃ or CaO. Specifically, the stabilized ZrO ₂ contains at least 12.0 mass% to 15.5 mass% of Y ₂ O ₃ , or 10.2 mass% to 11.4 mass% of CaO. By making the composition of the crucible 5 stabilized ZrO ₂ having a low thermal conductivity as described above, crystal defects occurring during crystal growth are easily expelled to the outer periphery of the crystal, thereby preventing polycrystallization of the beta-type Ga ₂ O ₃ single crystal during crystal growth. "Stabilized _ZrO2 " refers to _ZrO2 in which a high-temperature phase (typically a cubic or tetragonal solid solution) can exist stably up to room temperature by adding _{Y2O3 ,} CaO, magnesium oxide (MgO), aluminum oxide (alumina: _{Al2O3 )} , etc. to _ZrO2 . Note that the oxides that are solid-solved in stabilized _ZrO2 are not limited to _{Y2O3 ,} CaO, _MgO , and _Al2O3 .

<Thermal spray coating>
(composition)
The surface on the inner circumferential surface side of the crucible is coated with a sprayed film containing both or either of Rh and Pt. For example, the sprayed film is preferably made of a Pt-Rh alloy containing 10% by mass to 30% by mass of Rh. For example, in the crucible 5 of the first embodiment shown in FIG. 1, it is coated with a sprayed film 5b made of a platinum-rhodium alloy (Pt-Rh alloy) containing 10% by mass to 30% by mass of Rh. The thickness of the sprayed film 5b is 100 μm to 500 μm. The sprayed film 5b preferably coats the entire surface on the inner circumferential surface side of the crucible 5. However, even if a part of the surface is not coated with the sprayed film 5b or the composition of the sprayed film 5b is partially different, it does not deviate from the scope of the present disclosure.

The above-mentioned thermal spraying can be performed by a conventionally known method, for example, plasma spraying. For example, the above-mentioned thermal spraying can be performed by supplying the thermal spray material, which is made by heating the above-mentioned Pt-Rh alloy to molten particles or particles close to that (for example, particle diameter: 45 to 300 μm), toward the inner peripheral surface of the side wall portion 5a from a direction inclined at 30 to 45 degrees with respect to the axial direction of the crucible 5 using a thermal spray nozzle. At this time, for example, it is preferable to set the distance from the tip of the thermal spray nozzle to the inner peripheral surface side of the crucible 5 to 20 to 120 mm along the direction in which the tip of the nozzle faces. Furthermore, the thickness of the thermal spray film 5b can be determined by controlling the supply speed of the thermal spray material. For example, the supply speed of the thermal spray material may be 50 to 75 g/min. The porosity described later can be determined by controlling the angle of the thermal spray nozzle and the supply speed of the thermal spray material. The surface roughness Rz described later can be increased by increasing the particle diameter of the thermal spray material.

By having the Rh content in the Pt-Rh alloy that constitutes the sprayed film 5b be 10 mass% or more, cracking and chipping of the crucible 5 during crystal growth can be more adequately suppressed. By having the Rh content in the Pt-Rh alloy that constitutes the sprayed film 5b be 30 mass% or less, cracking and chipping of the crucible 5 during crystal growth can be more adequately suppressed without increasing the cost of the crucible 5. It is more preferable that the sprayed film 5b be made of a Pt-Rh alloy containing 20 mass% or more and 30 mass% or less of Rh.

If the thickness of the sprayed film 5b is less than 100 μm, the sprayed film 5b may peel off from the side wall portion 5a, and cracking and chipping of the crucible 5 during crystal growth may not be sufficiently suppressed. If the thickness of the sprayed film 5b exceeds 500 μm, the adverse effect of increased cost of the crucible 5 may outweigh the cost reduction and other benefits obtained by suppressing cracking and chipping of the crucible 5 during crystal growth. The thickness of the sprayed film 5b is preferably 200 μm or more and 500 μm or less.

The thickness of the sprayed coating is measured in accordance with JIS H 8401:1999 (Testing method for thickness of sprayed products). Specifically, it can be measured by a direct method using a micrometer (for example, product name (product number): "U-shaped micrometer PMU100-25" manufactured by Mitutoyo Corporation, or product name (product number): "Laser digital micrometer LSM-501S" manufactured by Mitutoyo Corporation) to determine the difference between the crucible thickness before spraying and the crucible thickness after spraying. The concentration of Rh in the Pt-Rh alloy can be determined when preparing the sprayed material.

(Vacancy)
Here, the sprayed film preferably has pores. The porosity, which is the volume ratio of the pores in the sprayed film, is preferably 30% by volume or more and 50% by volume or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth. FIG. 2 is an enlarged cross-sectional view of a main part for explaining a main part of a crucible of a second embodiment used in the single crystal growth apparatus of FIG. 1. In the crucible of the second embodiment shown in FIG. 2, the sprayed film 5b present on the inner peripheral surface side of the side wall portion 5a has pores 5c. The porosity, which is the volume ratio of the pores 5c in the sprayed film 5b, is preferably 30% by volume or more and 50% by volume or less.

The porosity is measured in accordance with JIS K 7112:1999 Method A (underwater displacement method). Specifically, the density of the crucible is first measured before and after spraying to calculate the actual density of the sprayed film. The composition of the sprayed film is then determined using an energy dispersive X-ray device attached to a transmission electron microscope (SEM-EDX: Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy), and the ideal density is calculated from this composition. The porosity can be calculated by dividing the actual density by the ideal density x 100.

Since the crucible of the second embodiment is made of _the above-mentioned stabilized ZrO2, it is difficult to deform due to thermal contraction during crystal growth and cooling after crystal growth. However, even if _the beta-type _Ga2O3 single crystal present in the crucible presses the side wall portion 5a due to some thermal contraction of the crucible, especially during cooling after crystal growth, the pores 5c contained in the sprayed film 5b are crushed, thereby suppressing the occurrence of cracks, chipping, etc. of the crucible. If the porosity is less than 30% by volume, the effect of suppressing cracks and chipping of the crucible by only crushing the pores 5c may not be sufficient. If the porosity is more than 50% by volume, it may be difficult to spray such a sprayed film 5b on the side wall portion 5a.

(Surface roughness)
The surface roughness Rz of the surface on the inner peripheral surface side of the crucible is preferably 300 μm or more and 500 μm or less. In this case, the sprayed film preferably has pores. The porosity, which is the volume ratio of pores in the sprayed film, is preferably 10 vol.% or more and less than 30 vol.%. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth. FIG. 3 is an enlarged cross-sectional view of a main part of a crucible of a third embodiment used in the single crystal growth apparatus of FIG. 1. In the crucible of the third embodiment shown in FIG. 3, the surface roughness Rz of the surface on the inner peripheral surface side of the side wall portion 5a is 300 μm or more and 500 μm or less. The sprayed film 5b on the inner peripheral surface side of the side wall portion 5a has pores 5c. The porosity, which is the volume ratio of pores 5c in the sprayed film 5b, is 10 vol.% or more and less than 30 vol.%. The surface roughness Rz of the inner peripheral surface of the side wall portion 5a is preferably 300 μm or more and 400 μm or less.

The method for measuring the surface roughness Rz of the inner peripheral surface of the side wall portion 5a is as follows. That is, the surface roughness Rz can be measured by determining the maximum height (Rz) of the inner peripheral surface of the side wall portion 5a as defined in JIS B0601:2001. For example, a surface roughness measuring instrument (product name (product number): "Surface roughness measuring instrument SV-2100M4" manufactured by Mitutoyo Corporation, or product name (product number): "Surface roughness measuring instrument SURFCOM TOUCH 550" manufactured by Tokyo Seimitsu Co., Ltd.) is used. The surface roughness Rz can be measured by setting a measuring unit inside the crucible and performing roughness measurement using a display/control unit. The method for measuring the porosity can be the same as the method for measuring the porosity of the sprayed film of the crucible of the second embodiment.

The crucible of the third embodiment is made of _the above-mentioned stabilized ZrO2, so that it is difficult to deform due to thermal contraction during crystal growth and cooling after crystal growth. However, even if the beta-type _Ga2O3 single crystal in the _crucible presses the side wall portion 5a due to some thermal contraction of the crucible, especially during cooling after crystal growth, the convex portion existing on the surface of the inner peripheral surface side of the side wall portion 5a is crushed based on the surface roughness, so that the occurrence of cracks, chips, etc. of the crucible can be suppressed. Furthermore, the pores 5c contained in the sprayed film 5b are crushed, so that the occurrence of cracks, chips, etc. of the crucible can also be suppressed. If the above-mentioned surface roughness Rz is less than 300 μm, the effect of suppressing cracks and chips of the crucible due to the convex portion being crushed may not be sufficient. If the surface roughness Rz exceeds 500 μm, the strength of the crucible itself is reduced, which may cause the convex parts to break during crystal growth, leading to cracks and chipping of the crucible. Furthermore, if the porosity is less than 10% by volume, the effect of suppressing cracks and chipping of the crucible due to crushing of the pores 5c may not be sufficient.

Here, in the crucible of the second embodiment, it is also preferable that the surface roughness Rz of the surface is 300 μm or more and 500 μm or less. This makes it possible to further suppress the occurrence of cracks, chipping, etc. during crystal growth based on the presence of the above-mentioned surface protrusions and voids 5c. By having the surface roughness Rz be 300 μm or more, the effect of suppressing cracking and chipping of the crucible due to the convex parts being crushed can be sufficiently obtained. By having the surface roughness Rz be 500 μm or less, the effect of suppressing cracking and chipping of the crucible during crystal growth, etc. can be sufficiently obtained without reducing the strength of the crucible itself. In the crucible of the second embodiment, the aspect in which the surface roughness Rz of the surface is 300 μm or more and 500 μm or less can have the same configuration as the aspect in which the porosity is 30 volume % or more and 50 volume % or less in the crucible of the third embodiment.

(First and second membranes)
The sprayed film is preferably made of a first film and a second film. The first film preferably covers the surface. The first film is preferably made of Rh or a Pt-Rh alloy mainly composed of Rh. The second film preferably covers the first film. The second film is preferably made of Pt or a Pt-Rh alloy mainly composed of Pt. The thickness of the sprayed film is preferably 100 μm or more and 500 μm or less in total including the first film and the second film. This not only suppresses the occurrence of cracks, chips, etc. during crystal growth, but also suppresses the incorporation of Rh into the beta type Ga ₂ O ₃ single crystal.

FIG. 4 is an enlarged cross-sectional view of a main part of a crucible of a fourth embodiment used in the single crystal growth apparatus of FIG. 1. In the crucible of the fourth embodiment shown in FIG. 4, the sprayed film is made of a first film 5b1 and a second film 5b2. The first film 5b1 covers the surface on the inner circumferential side of the side wall portion 5a. The first film 5b1 is made of Rh or a Pt-Rh alloy mainly composed of Rh, and is preferably made of Rh, for example. The second film 5b2 covers the first film 5b1. The second film 5b2 is made of Pt or a Pt-Rh alloy mainly composed of Pt, and is preferably made of Pt, for example. The thickness of the sprayed film is 100 μm or more and 500 μm or less, in total, for the first film 5b1 and the second film 5b2. It is more preferable that the thickness of the above-mentioned sprayed film is 100 μm or more and 300 μm or less in total of the first film 5b1 and the second film 5b2. If the total thickness of the first film 5b1 and the second film 5b2 is less than 100 μm, the first film 5b1 and the second film 5b2 may peel off from the side wall portion 5a, and the effect of suppressing cracking and chipping of the crucible 5 during crystal growth based on the sprayed film being composed of the first film 5b1 and the second film 5b2 may not be sufficient. If the total thickness of the first film 5b1 and the second film 5b2 exceeds 500 μm, the adverse effect of increasing the cost of the crucible 5 may outweigh the effect of reducing costs and the like obtained by suppressing cracking and chipping of the crucible 5 during crystal growth. The method for measuring the thickness of the first film and the second film can be the same as the method for measuring the thickness of the sprayed film of the crucible in the first embodiment.

As shown in FIG. 4, it is preferable that both the first film 5b1 and the second film 5b2 have pores 5c. It is preferable that the first film porosity, which is the volume ratio of the pores 5c in the first film 5b1, and the second film porosity, which is the volume ratio of the pores 5c in the second film 5b2, are both 30 volume % or more and 50 volume % or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth based on the above-mentioned action of the pores 5c. The method for measuring the first film porosity and the second film porosity can be the same as the method for measuring the porosity of the sprayed film of the crucible in the second embodiment.

In the crucible of the fourth embodiment, the sprayed film is made of the first film 5b1 and the second film 5b2. The first film 5b1 is made of Rh or a Pt-Rh alloy mainly composed of Rh, and the second film 5b2 is made of Pt or a Pt-Rh alloy mainly composed of Pt. The first film 5b1 covers the inner peripheral surface of the side wall 5a, and the second film 5b2 covers the first film 5b1. Therefore, the Rh in the sprayed film does not directly contact the beta type Ga ₂ O ₃ single crystal in the crucible, or even if it does, the amount of contact is very small, so that it is possible to suppress the incorporation of Rh into the beta type Ga ₂ O ₃ single crystal during crystal growth, etc.

Here, in the crucible of the fourth embodiment, the sprayed film is composed of the first film 5b1 and the second film 5b2. Therefore, by considering the first film 5b1 and the second film 5b2 together, the sprayed film can be composed of a Pt-Rh alloy containing 10% by mass or more and 30% by mass or less of Rh. For example, in the crucible of the fourth embodiment, the sprayed film can be composed of the first film 5b1 composed of Rh and the second film 5b2 composed of Pt, and the thickness of the first film 5b1 can be one-third that of the second film 5b2. As a result, the crucible of the fourth embodiment can include a sprayed film composed of a Pt-Rh alloy containing 10% by mass or more and 30% by mass or less of Rh. As described above, the thickness of the sprayed film is 100 μm or more and 500 μm or less, the total thickness of the first film 5b1 and the second film 5b2.

Furthermore, in a crucible in which the sprayed film is composed of a first film and a second film, the surface roughness Rz of the surface on the inner peripheral side is preferably 300 μm or more and 500 μm or less. In this case, it is preferable that both the first film and the second film have pores. The first film porosity, which is the volume ratio of the pores in the first film, and the second film porosity, which is the volume ratio of the pores in the second film, are both preferably 10 volume% or more and less than 30 volume%. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth. Figure 5 is an enlarged cross-sectional view of the main part of a crucible of the fifth embodiment used in the single crystal growth apparatus of Figure 1. In the crucible of the fifth embodiment shown in Figure 5, the surface roughness Rz of the surface on the inner peripheral side of the side wall portion 5a is 300 μm or more and 500 μm or less. The first film 5b1 and the second film 5b2 on the inner circumferential surface side of the side wall portion 5a each have pores 5c. The first film porosity and the second film porosity, which are the volume ratios of the pores 5c in the first film 5b1 and the second film 5b2, are 10 volume % or more and less than 30 volume %. The surface roughness Rz of the surface on the inner circumferential surface side of the side wall portion 5a is preferably 300 μm or more and 400 μm or less.

According to the crucible of the fifth embodiment, like the crucible of the third embodiment, the occurrence of cracks, chipping, etc. during crystal growth can be further suppressed based on the presence of the convex parts and holes 5c on the inner peripheral surface side. Furthermore, like the crucible of the fourth embodiment, the Rh in the sprayed film does not directly contact the beta type _{Ga2O3 single} crystal in the crucible, or even if it does, the contact is very slight, so that it is possible to suppress the incorporation of Rh into the beta type _{Ga2O3 single} crystal during crystal growth, etc.

Here, in the crucible of the fourth embodiment, it is also preferable that the surface roughness Rz of the surface is 300 μm or more and 500 μm or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth based on the presence of the above-mentioned surface protrusions and voids 5c. Note that in the crucible of the fourth embodiment, the embodiment in which the surface roughness Rz of the surface is 300 μm or more and 500 μm or less has the same configuration as the embodiment in which the first membrane porosity and the second membrane porosity are 30 volume % or more and 50 volume % or less, respectively, in the crucible of the fifth embodiment.

<Crucible holding stand>
As shown in Fig. 1, the single crystal growth apparatus 100 includes a crucible holder 6 for holding a crucible 5. The crucible holder 6 is in contact with the bottom of the crucible 5 to hold the crucible 5. The crucible holder 6 may have a cylindrical appearance. The material of the crucible holder 6 is not particularly limited, but may be, for example, quartz, alumina, zirconia, silicon carbide, or the like. The outer diameter of the crucible holder 6 depends on the diameter of the crucible 5 to be supported, but is, for example, 75 mm or more and 200 mm or less.

(Heating device)
The heating device 7 is installed for the purpose of heating the crucible 5. The heating device 7 can be, for example, a conventionally known electric heater (hereinafter, also simply referred to as "heater"). The heater is, for example, two units, and the two units are arranged to surround the outer periphery of the crucible 5. The output of the heater may be controlled independently for each unit. In particular, the heater may be divided into a plurality of parts in a direction perpendicular to the axis of the crucible 5 for each unit, thereby forming a multi-stage structure. In this case, it is preferable that the output of the heater is controlled independently for each of the multi-stage parts. This allows the temperature of the contents in the crucible 5 to be precisely adjusted along the axial direction of the crucible 5. For example, the heater output is controlled independently for each of the multi-stage parts to heat the diameter-increasing portion 52 and the straight body portion 53, thereby stabilizing the growth rates of the crystals growing in the diameter-increasing portion 52 and the straight body portion 53.

Although not shown in the figure, the single crystal growth apparatus 100 can be equipped with a thermocouple capable of measuring the temperature of the crucible 5 heated by the heater. A plurality of thermocouples may be arranged on the outside of the crucible 5 along the axial direction. The thermocouple may be, for example, a known temperature monitor.

[Method for producing beta-type gallium trioxide single crystal substrate]
The manufacturing method of the beta-type gallium trioxide single crystal substrate (beta-type Ga ₂ O ₃ single crystal substrate) according to this embodiment is preferably a beta-type Ga ₂ O ₃ single crystal substrate using the crucible described above. That is, the manufacturing method preferably includes a step of preparing the crucible, a step of obtaining a beta-type gallium trioxide single crystal (beta-type Ga ₂ O ₃ single crystal) by a vertical boat method using the crucible, and a step of obtaining a beta-type Ga ₂ O ₃ single crystal substrate having a circular main surface by processing the beta-type Ga 2 O ₃ single crystal. The manufacturing method of the beta-type Ga ₂ O ₃ single crystal substrate having such characteristics reduces the cracking and chipping of the crucible during crystal growth, etc., so that the beta-type _{Ga 2 O 3} single crystal substrate can be obtained with a high yield.

Fig. 6 is a flow chart showing an example of a method for manufacturing a beta type _Ga2O3 single crystal substrate according to this embodiment. The method for manufacturing a beta type _{Ga2O3 single} crystal substrate according to this embodiment preferably includes a beta type _{Ga2O3 single} crystal manufacturing step S100 and _a beta type _{Ga2O3 single} crystal substrate manufacturing step _{S200 shown in the flow chart of Fig. 6. According to Fig. 6, the method for manufacturing a beta type Ga2O3 single} crystal substrate according to this embodiment preferably includes, more specifically, as the beta type _{Ga2O3 single} crystal manufacturing step S100, a step (first step: preparation step S110) of preparing a single crystal growth apparatus including at least a cylindrical crucible and a heating device arranged so as to surround the outer periphery of the crucible. In the preparation step S110, in addition to the single crystal growth apparatus and the crucible constituting it, a seed crystal and _a block-shaped _Ga2O3 bulk body are preferably also prepared.

_The beta type _Ga2O3 single crystal manufacturing process S100 preferably includes a step (second step: raw material charging step S120) of accommodating the seed crystal at the bottom of the crucible and accommodating the _{Ga2O3 bulk} body above the seed crystal in the crucible. In the raw material charging step _{S120, the Ga2O3 bulk body is preferably accommodated above the seed crystal in the crucible. The beta type Ga2O3 single crystal manufacturing} process S100 preferably includes a step (third step: raw material melting step S130) of heating the crucible with the heating device, melting a part of the _{Ga2O3 bulk} body and the seed _crystal to obtain _{a Ga2O3 melt, and contacting the Ga2O3 melt with} the remaining part of the seed crystal. Furthermore, the beta-type _{Ga2O3 single} crystal manufacturing process S100 preferably includes a process (fourth process: _{Ga2O3 single} crystal growing process S140) of obtaining a beta-type _{Ga2O3 single} crystal by growing a crystal from _{the Ga2O3} melt on the remaining part of the seed crystal.

The manufacturing method of the beta type _{Ga2O3 single} crystal substrate according to this embodiment can include a cutting step, a peripheral grinding step, and a polishing step as described below as a beta type _{Ga2O3 single} crystal substrate manufacturing step S200. In the beta type _{Ga2O3 single} crystal substrate manufacturing step S200, the above steps are performed in this order to obtain a beta type _{Ga2O3 single} crystal substrate.

Hereinafter _, each step included in the manufacturing method of the beta type _Ga2O3 single crystal substrate according to the present embodiment will be described with reference to Fig. 1 and Fig. 6. According to the manufacturing method of the beta type _{Ga2O3 single} crystal substrate, first, a crucible 5 applied to the single crystal growth apparatus 100 shown in Fig. 1 is used to grow a beta type _Ga2O3 single crystal by the vertical boat method. As the crucible 5, any one of the crucibles of the first to fifth aspects described above can be used. Hereinafter, the vertical boat method is abbreviated as the _VB method. The VB method includes the vertical Bridgman method and the vertical temperature gradient solidification method.

<Beta type _{Ga2O3 single} crystal manufacturing process S100>
(Preparation step S110)
As shown in Fig. 1 and Fig. 6, in _the beta type _Ga2O3 single crystal manufacturing process S100, a process (preparation process S110) of preparing a single crystal growth apparatus 100 including at least a cylindrical crucible 5 and a heating device 7 arranged so as to surround the outer periphery of the crucible ₅ is first performed. In the preparation process S110, in addition to the above-mentioned single crystal growth apparatus 100 for manufacturing the beta type _Ga2O3 single crystal ₈₁ , it is preferable that a seed crystal 8a and a block-shaped _{Ga2O3 bulk} body are also prepared. The seed crystal _8a is made of a beta type _Ga2O3 single crystal. The _Ga2O3 bulk body may be made of _{polycrystalline Ga2O3} . The seed crystal 8a and the block-shaped _{Ga2O3 bulk} body may be prepared by a conventionally known method or by obtaining commercially available products.

In the preparation step S110, the crucible 5 is prepared as any one of the crucibles of the first to fifth aspects described above. In the crucibles of the first to fifth aspects, the above-mentioned features can be provided by using a conventionally known method. That is, a crucible 5 having a side wall portion 5a with a thickness of 1 to 10 mm and an inner diameter of the straight body portion 53 of 100 mm or more can be manufactured by a conventionally known method. In this case, the composition of the crucible 5 can be, for example, stabilized ZrO ₂ containing at least 12.0 mass % to 15.5 mass % Y ₂ O ₃ or 10.2 mass % to 11.4 mass % CaO.

Furthermore, by carrying out plasma spraying on the crucible 5 using a spray material prepared under the following conditions, for example, the surface on the inner circumferential surface side of the side wall portion 5a can be coated with a sprayed film 5b.
Thermal spray material: Pt-Rh alloy thermal spray material containing 10-30 mass% Rh Particle size: 45-300 μm
Supply rate of thermal spray material: 50 to 75 g/min. Orientation of thermal spray nozzle: 30 to 45 degrees with respect to the axial direction of the crucible. Distance between the thermal spray nozzle and the inner peripheral surface of the side wall of the crucible: 20 to 120 mm.

By controlling the supply speed of the spray material, the thickness of the sprayed film 5b can be set to, for example, 100 to 500 μm. By controlling the angle of the spray nozzle and the supply speed of the spray material, the porosity in the sprayed film 5b can be adjusted to 10 to 50 volume %. By controlling the particle size of the spray material, the surface roughness Rz of the surface on the inner circumferential side of the side wall portion 5a of the crucible 5 can be adjusted to 300 to 500 μm.

When preparing the crucible of the fourth embodiment and the crucible of the fifth embodiment, a first spray material made of Rh or a Pt-Rh alloy mainly composed of Rh and having a particle size of 45 to 300 μm, and a second spray material made of a Pt-Rh alloy mainly composed of Pt and having a particle size of 45 to 300 μm can be used as the spray material. In this case, by performing plasma spraying using the first spray material, the surface on the inner circumferential side of the side wall portion 5a of the crucible 5 can be coated with a first film. Furthermore, by performing plasma spraying using the second spray material, the first film can be coated with a second film. In this case, by controlling the supply speed of the first and second spray materials, the angle of the spray nozzle, and the particle diameter of the first and second spray materials, it is possible to adjust the thickness of the first and second films, the porosity of the first film, the porosity of the second film, and the surface roughness Rz of the surface on the inner circumferential side of the side wall portion 5a of the crucible 5.

(Raw material charging process S120)
The raw material charging step S120 is a step of placing the seed crystal at the bottom of the crucible and placing a block-shaped Ga ₂ O ₃ bulk body above the seed crystal in the crucible. In S120, it is preferable that _{solid B2O3} is also accommodated in the crucible 5 above the seed crystal 8a along with the massive _{Ga2O3 bulk} body. In the raw material charging step S120, various raw materials for crystal growth are charged into the crucible using the growth apparatus 100. First, beta-type Ga ₂ A seed crystal 8a consisting of an _O3 single crystal is charged. Next, a plurality of _Ga2O3 bulk _bodies made of polycrystalline _Ga2O3 are charged into the diameter increasing portion 52 and the straight body portion ₅₃ of the crucible 5 and stacked. In the raw material charging step S120, When a plurality of _Ga2O3 bulk bodies are charged into the crucible 5, it is preferable to add a predetermined amount of Sn or _{Si. This makes it possible to obtain a beta type Ga2O3 single crystal by the beta type Ga2O3 single crystal} manufacturing process S100. From the Ga ₂ O ₃ single crystal 81, a beta type Ga ₂ O ₃ single crystal substrate containing the above Sn or Si as a dopant is obtained. When Sn or Si _is added, the concentration of the dopant is, for example, 1.0×10 ¹⁸ cm ⁻³ (5.0 _× 10 ¹⁷ cm ⁻³ or more and 4.0×10 It is preferable to adjust the amount of addition so that the density of the SiO 2 is ¹⁹ cm ⁻³ or less.

(Raw material melting step S130)
The raw material melting step S130 is a step of heating the crucible with the heating device, melting the _{Ga2O3 bulk} body and a part of the _seed crystal to obtain a _Ga2O3 melt, and bringing the Ga2O3 melt into contact with the remaining part of the seed crystal. The purpose of the raw material melting step _{S130 is to melt the Ga2O3 bulk body} and a part of the seed crystal 8a to bring the remaining part of the seed crystal 8a into contact with the _Ga2O3 melt ₈₂ when growing a crystal using the _single crystal growing apparatus 100. This allows a beta-type _{Ga2O3 single} crystal 81 to be grown on the remaining part of the seed crystal 8a in the next step, _{the Ga2O3} single crystal growing step S140. In the raw material melting step S130, specifically, the crucible 5 containing the seed crystal 8a and the _{Ga2O3 bulk} body therein is supported by the crucible holder 6. Then, a current is supplied to the heating device 7 to heat the crucible 5. This melts the _{Ga2O3 bulk} body to become a _Ga2O3 melt 82. Next, a part of the seed crystal 8a also melts, and the remaining part of the seed crystal _8a and _{the Ga2O3} melt 82 come into contact with each other at the interface.

( _{Ga2O3 single} crystal growth step S140)
The _Ga2O3 single crystal growth step S140 is a step of growing a crystal from _{the Ga2O3} melt on the remaining part of the seed crystal to obtain a beta type _{Ga2O3 single} crystal. In the _{Ga2O3 single} crystal growth step S140, for example, the crucible ₅ is gradually lowered downward (towards the seed crystal housing part 51) along its axis relative to the heating device 7, so that a temperature gradient is formed in the crucible 5 such that the temperature on the seed crystal 8a side is low and the temperature on _{the Ga2O3} melt 82 side is high. This allows the _Ga2O3 melt ₈₂ in contact with the seed crystal 8a to be solidified, and _the beta type _{Ga2O3 single} crystal 81 to be continuously grown from the _Ga2O3 melt 82 on the remaining part of the seed crystal 8a. At this time, the temperature on _{the Ga2O3} melt 82 side is, for example, 1800 to 1820° C. The temperature gradient at the interface between _{the Ga2O3} melt 82 and the growing beta type _{Ga2O3 single} crystal 81 is, for example, 3 to 8° C./cm. The speed at which the crucible 5 is pulled downward along its axis is not particularly limited, but can be, for example, 0.1 to 2 mm/hour.

In _{the Ga2O3} single crystal growth step S140, the crucible 5 is pulled downward along its axis relative to the heating device 7, so that the interface between _the beta type _Ga2O3 single crystal 81 and the _Ga2O3 melt ₈₂ rises to the liquid _{B2O3 side} , and the _Ga2O3 melt 82 is solidified as the beta type _Ga2O3 single crystal 81. As a result, the crystal growth of _the beta type _{Ga2O3 single} crystal 81 continues until the solidification of _{the Ga2O3 melt 82} remaining in the straight body part 53 of the crucible 5 is completed. In this manner, an ingot of the beta type _{Ga2O3 single} crystal 81 can be obtained.

<Beta type _{Ga2O3 single} crystal substrate manufacturing process S200>
The manufacturing method of the beta type _{Ga2O3 single} crystal substrate includes a step (beta type _Ga2O3 single crystal substrate manufacturing step S200) of obtaining a beta type _{Ga2O3 single} crystal substrate having a circular main surface by processing the beta type _{Ga2O3 single} crystal obtained by the _{Ga2O3 single} crystal growth step S140 as shown in Fig. _{6. The beta type Ga2O3 single crystal} substrate manufacturing step S200 includes the following cutting step, outer circumference grinding step, and polishing step, and the beta type _{Ga2O3 single} crystal substrate can be obtained by performing these steps in this order.

The cutting step is a step of slicing the ingot made of the beta type Ga ₂ O ₃ single crystal taken out of the crucible into a wafer having a predetermined thickness in order to obtain a beta type Ga ₂ O ₃ single crystal substrate from the ingot. Furthermore, the outer periphery grinding step is a step of obtaining a beta type Ga ₂ O ₃ single crystal substrate having a main surface having a circular shape by grinding the outer periphery of the wafer. The outer periphery grinding step may include, for example, a step of performing chamfering. The cutting step and the outer periphery grinding step may use a conventionally known cutting method and outer periphery grinding method. Furthermore, the polishing step is a step of mirror-finishing the center part of the main surface. The polishing step may use a conventionally known polishing method. By the polishing step, the center part may have a surface roughness Ra of 10 nm or less as specified in, for example, JIS B 0681-2:2018.

<Action and effect>
By carrying out each of the above steps, the beta type _{Ga2O3 single} crystal substrate according to this embodiment is manufactured. In the manufacturing method of the beta type _{Ga2O3 single} crystal substrate, the beta type _Ga2O3 single crystal is manufactured using any one of the crucibles of the first to fifth aspects described above, so that the crucible is less likely to break or chip during crystal _{growth. Therefore, the beta type Ga2O3 single crystal} substrate can be obtained with a high yield.

[Beta-type gallium trioxide single crystal substrate]
The beta-type gallium trioxide single crystal substrate (beta-type _{Ga2O3 single} crystal substrate) according to this embodiment is a beta-type _{Ga2O3 single} crystal substrate having a circular main surface. The diameter of the beta-type _{Ga2O3 single} crystal substrate is 100 mm or more. The main surface is the (001) plane of the beta-type _{Ga2O3 single} crystal. Or the main surface is a plane having an off angle of more than 0° and not more than 10° from the (001) plane of the beta-type _{Ga2O3 single} crystal, and an off direction in the [010] direction of the _beta -type _{Ga2O3 single} crystal or a direction perpendicular to the [010] direction. The beta-type _Ga2O3 single crystal substrate contains both or either one of rhodium (Rh) and iridium (Ir). The Rh concentration and the Ir concentration are each less than 3 ppm by mass as measured by glow discharge mass spectrometry (GDMS). The beta type _{Ga2O3 single} crystal substrate having such characteristics contains very small amounts of the Rh and Ir, and therefore has excellent electrical and optical properties.

The present inventors have focused on making the concentration of rhodium and iridium, which may be contained in the beta type _{Ga2O3 single} crystal substrate and may inhibit the good electrical and optical properties of the substrate because they are not of the same group as gallium ( _Ga ), extremely small in the substrate. Specifically, in producing a beta type _{Ga2O3 single} crystal for obtaining a beta type _Ga2O3 single crystal substrate, Rh and Ir are prevented from directly contacting the beta type _{Ga2O3 single} crystal and the _Ga2O3 melt that is the raw material for the beta type _Ga2O3 single crystal. More specifically, for example, a beta type _Ga2O3 single crystal is produced using the crucible of the fifth embodiment described above, and a beta type _{Ga2O3 single crystal} substrate is obtained from _the beta type _Ga2O3 single crystal. As a result, the inventors have devised a beta type Ga ₂ O ₃ single crystal substrate in which the Rh concentration and the Ir concentration are both less than 3 mass ppm, and have completed the present disclosure.

<Diameter>
7 is a schematic diagram for explaining the beta type _Ga2O3 single crystal substrate according to this embodiment. In the beta type _{Ga2O3 single} crystal substrate 1 shown in FIG. 7, the diameter is 100 mm or more. In particular _, the diameter of the beta type _Ga2O3 single crystal substrate ₁ is preferably 100 mm or more and 155 mm or less. The beta type _{Ga2O3 single} crystal substrate 1 having a diameter of 100 mm or more and 155 mm or less is preferably 101.6 mm or 152.4 mm, in other words, preferably 4 inches or 6 inches. As a result, the large-diameter beta type _{Ga2O3 single} crystal substrate having a diameter of 100 mm or more and 155 mm or less can be excellent in both electrical properties and optical properties. Here, the diameter of the beta-type _{Ga2O3 single} crystal substrate is determined based on the circular shape before the formation of the orientation flat (hereinafter also referred to as "OF"), index flat (hereinafter also referred to as "IF"), etc., even if the main surface does not have a geometrically circular shape due to the influence of the orientation flat (hereinafter also referred to as "OF"), index flat (hereinafter also referred to as "IF"), etc. As described above, the diameter of the _{beta-type Ga2O3 single} crystal substrate can be measured by using a conventionally known outer diameter measuring device such as a caliper. The definition of "circular shape" representing the shape of the main surface in this specification will be described later.

<Main surface>
(Circular)
_The beta-type _Ga2O3 single crystal substrate 1 has a circular main surface 10 as described above. In this specification, the term "circular shape" representing the shape of the main surface includes a geometrical circular shape, as well as a shape in which the main surface does not form a geometrical circular shape due to at least one of a notch, OF, or IF being formed on the periphery of the main surface 10. Here, the term "shape in which the main surface does not form a geometrical circular shape" refers to a shape in which, among the line segments extending from any point on the periphery of the main surface 10 to the center of the main surface 10, the line segments extending from any point on the notch, OF, and IF to the center of the main surface are shorter in length. Furthermore, the term "shape in which the main surface does not form a geometrical circular shape" also includes a shape in which the lengths of all the line segments extending from any point on the periphery of the main surface 10 to the center of the main surface 10 are not necessarily the same due to the shape of the beta-type _{Ga2O3 single} crystal that is the raw material of the _beta -type _Ga2O3 single crystal substrate 1. In this case, the center of the main surface 10 refers to the position of the center of gravity, and the diameter of the beta-type _{Ga2O3 single} crystal substrate ₁ refers to the length of the longest line segment that extends from any point on the outer periphery of the beta-type _Ga2O3 single crystal substrate 1, passing through the center of the main surface 10, to another point on the outer periphery.

((001) surface of beta type _{Ga2O3 single} crystal)
The main surface 10 is the (001) plane of the beta type _{Ga2O3 single} crystal. Alternatively, the main surface 10 is a plane having an off angle of more than 0° and not more than 10° from the (001) plane of the beta type _{Ga2O3 single} crystal, and an off direction in the [010] direction of the beta type _{Ga2O3 single} crystal or a direction perpendicular to the [010] direction. This makes it possible to provide a beta type _{Ga2O3 single} crystal substrate 1 having the (001) plane of the beta type _Ga2O3 single crystal, which is widely used for forming optical devices, electronic devices _{, etc.} , as the main surface 10.

In this specification, the crystal plane of the main surface 10 has a precision error of ±0.5°. For example, when the main surface 10 is the "(001) plane" of a beta-type _{Ga2O3 single} crystal, it means that the main surface 10 may be a (001) just plane, or the main surface 10 may be a plane having an off angle of -0.5 to +0.5° from the (001) plane. The off angle and off direction from the (001) plane on the main surface 10 of _the beta-type _Ga2O3 single crystal substrate 1 can be measured by using a conventionally known crystal orientation measuring device (for example, product name (product number): "FSASIII", manufactured by Rigaku Corporation).

<Rhodium (Rh) and Iridium (Ir)>
The beta type _{Ga2O3 single} crystal substrate contains both or either of rhodium (Rh) and iridium (Ir). The concentration of Rh and the concentration of Ir are both less than 3 mass ppm in GDMS. The concentration of Rh and the concentration of Ir are both preferably 1 mass ppm or less in GDMS, more preferably 0.1 mass ppm or less, and even more preferably 0.01 mass ppm or less. The lower limit of the concentration of Rh and the concentration of Ir is that they are not detected in GDMS. The beta type _{Ga2O3 single} crystal substrate can be excellent in both electrical properties and optical properties by having the Rh and Ir be less than 3 mass ppm.

The Rh and Ir are known elements that may be contained in the beta type _Ga2O3 single crystal substrate. On the other hand, when the beta type _{Ga2O3 single} crystal substrate is obtained by using the crucible of the fifth embodiment and the manufacturing method of the beta type _{Ga2O3 single} crystal substrate, the concentration of Rh and the concentration of Ir can be easily made less than 3 mass ppm in _GDMS based on the material of the crucible and the structure of the sprayed film consisting of the first film and the second film. Therefore, the beta type _{Ga2O3 single} crystal substrate excellent in both electrical properties and optical properties can be obtained with good yield.

Glow Discharge Mass Spectroscopy (GDMS)
Hereinafter, a method for measuring the concentrations of Rh and Ir in the beta-type _{Ga2O3 single} crystal substrate using glow discharge mass spectrometry (GDMS) will be described. GDMS refers to a technique in which a glow discharge plasma is generated using an analytical sample as a cathode in a high-purity argon atmosphere, and the surface of the analytical sample is sputtered in the plasma, and the ionized constituent elements in the analytical sample are measured with a mass spectrometer. This makes it possible to qualitatively and quantitatively determine impurity elements, including Rh and Ir, other than Ga and O contained in the _beta -type _Ga2O3 single crystal substrate. As the ion source for the GDMS, either a flat cell or a pin-shaped cell is applied. The pin-shaped cell can be applied to an analytical sample that can be formed into a strip shape of approximately 2 mm square and 20 mm long. Specifically, it is used when analyzing Si single crystals, gallium arsenide (GaAs) single crystals, indium phosphide (InP) single crystals, etc., which can be prepared by cleavage. The flat cell can be applied to an analytical sample that can be formed into a disk shape with a diameter of about 10 mm, for example, when analyzing a polycrystalline body. In any case, it is preferable to select either a flat cell or a pin-shaped cell as the ion source of the GDMS in order to avoid contamination of the analytical sample with impurity elements from the outside. Since the beta-type _{Ga2O3 single} crystal substrate can be used to prepare a pin-shaped analytical sample with the cleavage in the longitudinal direction, it is preferable to prepare an analytical sample in the shape of a pin-shaped cell from the beta-type _{Ga2O3 single} crystal substrate and use this as the ion source of the GDMS.

The GDMS can be carried out, for example, as follows. First, a beta type _Ga2O3 single crystal substrate is obtained by the manufacturing method described later. The beta type _{Ga2O3 single} crystal substrate is then cleaved in the longitudinal direction to obtain a rectangular _Ga2O3 analysis sample having a size of 2 mm square and a length _of 20 mm, which is then placed on the sample placement section of the apparatus described below. Here, it is _preferable to clean the sample placement section in accordance with a conventional method to prevent contamination and to remove foreign matter, and to perform pre-sputtering for 60 minutes. The analysis value during pre-sputtering is the background.

Next, GDMS can be performed on the _Ga2O3 analysis sample placed on the sample placement surface under the following conditions. For Rh and Ir, which are elements other than Ga and O among the constituent elements of _{the Ga2O3} analysis sample, semi _- quantitative values can be calculated by correcting the ion intensity ratio between Ga and Rh or the ion intensity ratio between Ga and Ir with a relative sensitivity factor (RSF). For the relative sensitivity factor, values built into the software attached to the following device can be used.
Apparatus: Glow discharge mass spectrometer (product name (product number): VG-9000, manufactured by VG Elemental)
Ion source: Pin cell (cooled with liquid nitrogen during analysis)
Discharge area: diameter 10mm
Discharge gas: High purity argon (6N grade)
Discharge conditions: 2 mA, 1 kV (constant current mode)
Detector: Faraday cup and multiplier. Mass resolution: 4000 or more m/Δm (high resolution mode).

By analyzing _{the Ga2O3} analysis sample as described above, it is possible to qualitatively and quantitatively determine the Rh and Ir contained in _the beta type _Ga2O3 single crystal substrate. The detection limit of the GDMS is preferably 0.01 mass ppm.

(Transmittance and Carrier Concentration)
In the beta type _{Ga2O3 single} crystal substrate, the transmittance for light having a wavelength of 400 nm or more and 430 nm or less is preferably 70% or more. The carrier concentration measured at 25°C in the Hall measurement by the Van der Pauw method is preferably 1 x ¹⁰¹⁷ cm ^-3 or more and 1.0 x ¹⁰¹⁹ cm ^-3 or less. This makes it possible to achieve better electrical and optical properties.

As described above, in the beta type _{Ga2O3 single} crystal substrate, the transmittance for light having a wavelength of 400 nm or more and 430 nm or less is preferably 70% or more. The transmittance is more preferably 75% or more, and even more preferably 80% or more. The upper limit of the transmittance is 100%, which is an ideal value. The transmittance can be obtained by measuring the transmittance of light for _the beta type _Ga2O3 single crystal substrate measured using an ultraviolet-visible-infrared spectrophotometer or the like. Hereinafter, the procedure for specifically obtaining the transmittance will be described with reference to FIG. 7.

First, for example _{, one beta type Ga2O3 single crystal substrate 1 is obtained based on the above-mentioned manufacturing method. From this one beta type Ga2O3 single crystal substrate} 1, a rectangular slice 10a (for example, 600 μm thick) with a size of 20 mm length x 20 mm width centered on its center O (for example, the center O of the main surface 10) is prepared, thereby obtaining a sample for transmittance measurement. Next, using an ultraviolet-visible-infrared spectrophotometer (product name (product number): "U-4000", manufactured by Hitachi High-Tech Corporation), light with a wavelength of 400 nm to 430 nm (for example, a wavelength of 427 nm) is perpendicularly incident on the center of the rectangular slice _10a . This allows the transmittance of the light in the beta type _Ga2O3 single crystal substrate 1 to be measured.

(Carrier concentration)
In this embodiment, the carrier concentration measured at 25°C in the Hall measurement by the Van der Pauw method is preferably ^{1x1017cm -3} or more and ^{1.0x1019cm -3} or less. Specifically, the carrier concentration measured at 25°C in the Hall measurement by the Van der Pauw method using the center of _the beta type _Ga2O3 single crystal substrate as the measurement target is preferably 1x1017cm ^{-3 or more and 1.0x1019cm-3 or less. If the carrier concentration is less than 1.0x1017cm-3 , when a} semiconductor device is created, no current flows, and the device may not operate. If the carrier concentration exceeds ^{1.0x1019cm -3 , it} suggests that the crystal contains ^{1.0x1019cm -3} or more of inactive impurities, which may adversely affect the operation of the device. In particular, the carrier concentration is more preferably 5.0×10 ¹⁷ cm ^-3 or more and 3.8×10 ¹⁸ cm ^-3 or less. This allows the n-type beta type Ga ₂ O ₃ single crystal substrate to have good electrical characteristics that can be used for various electronic devices and optical devices. The carrier concentration can be determined by the following measurement method.

Hereinafter, the procedure for determining the carrier concentration will be specifically described with reference to FIG. 7 and FIG. 8. FIG. 8 is an explanatory diagram for explaining a Hall measurement sample prepared using the center of a beta type _{Ga2O3 single} crystal substrate according to this embodiment in order to measure the carrier concentration in the substrate. First, as shown in FIG. 7 _, a single beta type _Ga2O3 single crystal substrate 1 is obtained based on the above-mentioned manufacturing method, for example. From the center of this single beta type _{Ga2O3 single} crystal substrate 1, a rectangular slice 10a (for example, 600 μm thick) having a length of 4 mm and a width of 4 mm is prepared with its center O (for example, the center O of the main surface 10) as the center. Next, as shown in FIG. 8, electrodes 21 made of an alloy containing gold and titanium are formed at the four corners of the rectangular slice 10a (surface to be measured), thereby obtaining a Hall measurement sample. Here, the shape of the electrode 21 is not limited to the rectangular shape shown in the figure, and may be a sector shape or a circle. The carrier concentration can be obtained by applying Hall measurement by the Van der Pauw method to the rectangular piece 10a equipped with such electrodes 21 in an atmosphere of 25° C. In this specification, the carrier concentration obtained by using the rectangular piece as the measurement object is defined as the carrier concentration of _the beta-type _Ga2O3 single crystal substrate measured at 25° C. in Hall measurement by the Van der Pauw method.

<Applications>
The beta type _Ga2O3 single crystal substrate according to this embodiment has excellent electrical and optical properties, and can be used as a substrate for forming optical devices and electronic devices. In particular, the beta type _{Ga2O3 single} crystal substrate is preferably used as a substrate for forming electronic devices based on its excellent electrical _properties .

The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited thereto. In the examples, a single crystal manufacturing apparatus as shown in FIG. 1 and a crucible having the essential parts as shown in FIGS. 2 to 5 were used to manufacture a beta-type Ga ₂ O ₃ single crystal substrate according to the flow chart shown in FIG. 6. In the following description, Samples 101 to 115, Samples 201 to 213, and Samples 301 to 313 are examples. Samples 10A to 10C, and Samples 20A to 20C are comparative examples.

Here, the "crystal outer diameter" of _the beta type _Ga2O3 single crystal in each of the following samples refers to the crystal outer diameter obtained by the following method: the outer diameter of _the beta type _Ga2O3 single crystal ingot taken out of the crucible is obtained at three points, namely, the position corresponding to the boundary between the diameter-increasing part and the straight body part (hereinafter also referred to as "measurement point 1"), the position 10 mm below the crystal growth end side of the ingot (hereinafter also referred to as "measurement point 2"), and the intermediate position between the measurement points 1 and 2 (hereinafter also referred to as "measurement point 3"), and the average value thereof is defined as the "crystal outer diameter".

[Production of _{Ga2O3 single} crystal substrate]
<Sample 10A>
According to the method disclosed in the above-mentioned Patent Document 1, it was attempted to manufacture a beta-type _{Ga2O3 single} crystal with the growth direction being the [001] direction by using the Vertical Bridgeman (VB) method. When obtaining _the beta-type _Ga2O3 single crystal, a crucible made of a Pt-Rh alloy containing 30 mass% Rh was used. The inner diameter of the straight body of the crucible was 105 mm. Furthermore, the thickness of the side wall of the crucible was 0.2 μm, and the surface roughness Rz of the surface on the inner circumferential surface side of the side wall was 20 μm. However, since the crucible was cracked during crystal growth, the beta-type _{Ga2O3 single} crystal could not be obtained, and therefore the beta-type _{Ga2O3 single} crystal substrate of sample 10A could not be obtained.

<Sample 10B>
A beta type _{Ga2O3 single} crystal was manufactured with the growth direction set to the [001] direction in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 10A. In this test example, no cracks were observed in the crucible. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 120 _mm . Furthermore, the above-mentioned cutting process, outer circumference grinding process, and polishing process were performed on the beta type _{Ga2O3 single} crystal in this order. As a result, _a beta type _Ga2O3 single crystal substrate of sample 10B was obtained. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 10B was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 10B was 25 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.02 mass ppm in the above-mentioned GDMS.

<Sample 10C>
A beta type _{Ga2O3 single} crystal was produced with the growth direction set to the [001] direction in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 10A, except that the thickness of the side wall of the crucible was set to 1.0 _mm . In this test example, no cracks were observed in the crucible. _{The crystal outer diameter of the beta type Ga2O3 single} crystal was 108 mm. Furthermore, the above-mentioned cutting process, outer circumference grinding process, and polishing process were performed on the beta type _Ga2O3 single crystal in this order. As a result, a beta type _Ga2O3 single crystal substrate of sample 10C was obtained. The diameter of the beta type _Ga2O3 single crystal substrate of sample 10C was 101.6 _mm , and the thickness was 650 _μm . The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 10C was 45 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.02 mass ppm in the above-mentioned GDMS.

<Sample 101>
(Preparation step S110)
First, a single crystal growth apparatus 100, a seed crystal 8a consisting of _a beta type _Ga2O3 single crystal, and a block-shaped _{Ga2O3 polycrystal} were prepared by a conventionally known method or by obtaining commercially available products. As the crucible 5 constituting the single crystal growth apparatus 100, a crucible was used which was made of stabilized ZrO2 with a purity of 89.2 mass% containing 10.8 mass% _CaO , had a side wall portion 5a with a thickness of 3 mm, and a sprayed film 5b with a thickness of 500 μm. More specifically, the inner diameter of the straight body portion of the crucible 5 was 105 mm. Furthermore, the surface roughness Rz of the surface on the inner peripheral surface side of the side wall portion 5a was 20 μm. The composition of the sprayed film 5b was a Pt-Rh alloy containing 30 mass% Rh, and the porosity of the sprayed film 5b was 10%.

(Raw material charging process S120 and raw material melting process S130)
Next, by a conventionally known method, a seed crystal 8a was accommodated in the seed crystal accommodation portion 51 of the crucible 5, and a chunk of _{Ga2O3 polycrystal} was accommodated above the seed crystal 8a. Specifically, a plurality of chunks of _{Ga2O3 polycrystal} were accommodated in the diameter increasing portion 52 and the straight body portion 53, and stacked. Next, the crucible 5, which accommodated the seed crystal 8a and the chunk of _{Ga2O3 polycrystal} inside, was supported by the crucible holder 6. Thereafter, a current was supplied to the heating device 7 to heat the crucible 5, and a portion of the _{Ga2O3 polycrystal} and the seed crystal 8a were melted, respectively _, to prepare a _Ga2O3 melt 82. Next, the remaining portion of the seed crystal 8a and _{the Ga2O3} melt 82 were brought into contact with each other at their interface.

( _{Ga2O3 single} crystal growth step S140)
Next, the crucible 5 was gradually pulled downward (to the bottom side) along its axis relative to the heating device 7, so that the temperature gradient was such that the temperature on the seed crystal 8a side of the crucible 5 was low and the temperature on the Ga ₂ O ₃ melt 82 side was high. As a result, a crystal was grown from the Ga ₂ O ₃ melt 82 onto the remaining part of the seed crystal 8a side with the growth direction being the [001] direction, to obtain a beta type Ga ₂ O ₃ single crystal 81. Furthermore, this operation was continued until the pulling distance reached 100 mm. The temperature of the interface between the growing beta type Ga ₂ O ₃ single crystal 81 and the Ga ₂ O ₃ melt 82 was 1800 to 1820°C. The temperature gradient at the interface was 5°C/cm. The speed at which the crucible 5 was pulled downward along its axis was 1 mm/hour. In this manner, an ingot of a beta type Ga ₂ O ₃ single crystal was obtained. The outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

( _{Ga2O3 single} crystal substrate manufacturing process S200)
Finally _, the beta-type _{Ga2O3 single} crystal ingot obtained in the _Ga2O3 single crystal growth step S140 was processed in each step of a cutting step, a peripheral grinding step, and a polishing step to obtain a beta-type _Ga2O3 single crystal substrate. First, in the cutting step, the ingot was sliced into a wafer having a thickness of ₇₀₀ μm using a conventionally known method. In the peripheral grinding step, the wafer was ground so as to be chamfered on the outer periphery using a conventionally known method to obtain a wafer having a main surface consisting of a central portion and an outer periphery surrounding the outer periphery of the central portion. Furthermore, in the polishing step, the central portion was polished using a conventionally known polishing method, and the surface roughness Ra of the central portion, for example, as specified in JIS B 0681-2:2018, was set to 8 nm.

In this manner, a beta type _{Ga2O3 single} crystal substrate of sample 101 was manufactured. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 101 was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 101 was 15 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS.

<Sample 102>
In the preparation step, a crucible was prepared in which the porosity of the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 20%, and the beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 101. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 105.8 _mm . Furthermore, the beta type _{Ga2O3 single} crystal substrate of sample 102 was obtained _from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 102 was 101.6 mm and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 102 was 20 mass ppm in the above-mentioned GDMS, and the concentration of Ir was 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 103>
In the preparation step, a crucible was prepared in which the porosity of the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 30%, and the beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 101. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 105.8 _mm . Furthermore, the beta type _{Ga2O3 single} crystal substrate of sample 103 was obtained _from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 103 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 103 was 18 ppm by mass in the above-mentioned GDMS, and the Ir concentration was 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 104>
In the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 200 μm thick, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 101. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample ₁₀₄ was obtained from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 104 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 104 was 17 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 105>
In the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 200 μm thick, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 102. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 105 was obtained from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample ₁₀₅ was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 105 was 25 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 106>
In the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 200 μm thick, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 103. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample ₁₀₆ was obtained from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 106 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 106 was 40 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 107>
In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method of obtaining the beta type _{Ga2O3 single} crystal substrate of sample 104. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, _a beta type _{Ga2O3 single} crystal substrate of sample 107 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 107 was 101.6 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 107 was 28 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 108>
In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and the beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 105. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, the beta type Ga2O3 _single crystal substrate of sample 108 was obtained _from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 108 was 101.6 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 108 was 15 mass ppm in the above-mentioned GDMS, and the concentration of Ir was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 109>
In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and the beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 104. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, the beta type Ga2O3 _single crystal substrate of sample 109 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample ₁₀₉ was 101.6 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 109 was 22 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was less than 0.01 _ppm by mass in the above-mentioned GDMS.

<Sample 110>
In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and the beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 105. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, the beta type Ga2O3 _single crystal substrate of sample 110 was obtained _from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 110 was 101.6 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 110 was 25 mass ppm in the above-mentioned GDMS, and the concentration of Ir was 0.02 mass ppm in the above-mentioned GDMS.

<Sample 111>
In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method of obtaining the beta type _{Ga2O3 single} crystal substrate of sample 106. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, the beta type _{Ga2O3 single} crystal substrate of sample 111 was obtained _from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 111 was 101.6 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 111 was 27 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 112>
A beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 111. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 112 was obtained from _the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 112 was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 112 was 20 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 113>
In the preparation step, a crucible was prepared in which the inner peripheral surface side of the side wall portion 5a was covered with a sprayed film consisting of the following first film 5b1 and second film 5b2, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 109. That is, in the preparation step of this test example, a first spray material was sprayed on the surface on the inner peripheral surface side of the side wall portion 5a of the crucible 5, thereby covering the surface with a first film 5b1 made of Rh, having a first film porosity of 30%, and having a thickness of 50 μm. Furthermore, a second spray material was sprayed on the first film 5b1, thereby covering the first film 5b1 with a second film 5b2 made of Pt, having a second film porosity of 30%, and having a thickness of 150 μm.

The outer crystal diameter of the beta type _{Ga2O3 single} crystal obtained in this way was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 113 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 113 was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 113 was less than 0.01 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 114>
A beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 113. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 114 was obtained from _the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 114 was 101.6 mm, and the _thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 114 was 0.08 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 115>
A beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 113. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 115 was obtained from _the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 115 was 101.6 mm, and the _thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 115 was 2.9 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 20A and Sample 20B>
Except for the inner diameter of the straight body of the crucible used for obtaining _{the Ga2O3 single} crystal being 156 mm, the beta type _{Ga2O3 single} crystal substrates of samples 20A and 20B were attempted to be manufactured in _the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrates of samples 10A and 10B. However, the crucible broke during crystal growth, and the beta type _{Ga2O3 single} crystal substrates of samples 20A and 20B could not be obtained.

<Sample 20C>
A beta type _{Ga2O3 single} crystal was produced with the growth direction set to the [001] direction in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 20A and sample 20B, except that the thickness of the side wall of the crucible was set to 1.0 _mm . In this test example, no cracks were observed in the crucible. _{The crystal outer diameter of the beta type Ga2O3 single crystal} was 165 mm. Furthermore, the above-mentioned cutting process, outer circumference grinding process, and polishing process were performed on the beta type _{Ga2O3 single} crystal in this order. As a result, a beta type _Ga2O3 single crystal substrate of sample 20C was obtained. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 20C was 152.4 mm, and the thickness was 650 μm. The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 20C was 38 ppm by mass in the above-mentioned GDMS, and the Ir concentration was 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 201>
In the preparation step _, a beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 101, except that a crucible with an inner diameter of the straight body part of ₁₅₆ mm was prepared. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, the beta type _{Ga2O3 single} crystal substrate of sample 201 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 201 was 152.4 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 201 was 15 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 202>
In the preparation step, a crucible was prepared in which the porosity of the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 20%, and the beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 201. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 157.1 _mm . Furthermore, the beta type _{Ga2O3 single} crystal substrate of sample 202 was obtained _from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 202 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 202 was 20 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth by heating, but cracks were observed during cooling after the crystal growth.

<Sample 203>
In the preparation step, a crucible was prepared in which the porosity of the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 30%, and the beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 201. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 157.1 _mm . Furthermore, the beta type _{Ga2O3 single} crystal substrate of sample 203 was obtained _from the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 203 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 203 was 23 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.01 mass ppm in the above-mentioned GDMS.

<Sample 204>
In the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 200 μm thick, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 201. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 204 was obtained from _the beta type _Ga2O3 single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 204 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 204 was 27 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 205>
In the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 200 μm thick, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 202. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 205 was obtained from _the beta type Ga2O3 _single crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 205 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 205 was 15 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.02 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 206>
In the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface side of the sidewall portion 5a was 200 μm thick, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _Ga2O3 single crystal substrate of sample 203. The crystal outer diameter of _the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 206 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 206 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta type Ga ₂ O ₃ single crystal substrate of sample 206 was 35 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 207>
In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method of obtaining the beta type _{Ga2O3 single} crystal substrate of sample 204. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, _a beta type _{Ga2O3 single} crystal substrate of sample 207 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 207 was 152.4 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 207 was 18 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 208>
In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and the beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 205. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, the beta type Ga2O3 _single crystal substrate of sample 208 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample ₂₀₈ was 152.4 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 208 was 25 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was less than 0.01 _ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 209>
In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and the beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 204. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, the beta type Ga2O3 _single crystal substrate of sample 209 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample ₂₀₉ was 152.4 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of sample 209 was 32 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was less than 0.01 _ppm by mass in the above-mentioned GDMS.

<Sample 210>
In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the sidewall portion 5a was prepared, and the beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of the sample 205. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, the beta type Ga2O3 _single crystal substrate of the sample 210 was obtained _from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of the sample ₂₁₀ was 152.4 mm, and the thickness was 650 μm. The concentration of Rh in the beta type _{Ga2O3 single} crystal substrate of the sample 210 was 26 ppm by mass in the above-mentioned GDMS, and the concentration of Ir was 0.02 ppm by mass in the above-mentioned GDMS.

<Sample 211>
In the preparation step, a crucible was prepared in which the inner peripheral surface side of the side wall portion 5a was covered with a sprayed film consisting of the following first film 5b1 and second film 5b2, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 209. That is, in the preparation step of this test example, a first spray material was sprayed on the surface on the inner peripheral surface side of the side wall portion 5a of the crucible 5, thereby covering the surface with a first film 5b1 made of Rh, having a first film porosity of 30%, and having a thickness of 50 μm. Furthermore, a second spray material was sprayed on the first film 5b1, thereby covering the first film 5b1 with a second film 5b2 made of Pt, having a second film porosity of 30%, and having a thickness of 150 μm.

The outer crystal diameter of the beta type _{Ga2O3 single} crystal obtained in this way was 157.1 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 211 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 211 was 152.4 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 211 was 0.02 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 212>
A beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample _211. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 212 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 212 was 152.4 mm, and the _thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 212 was less than 0.01 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 213>
A beta type _Ga2O3 single crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample _211. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 157.1 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 213 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 213 was 152.4 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 213 was 2.8 ppm by mass in the above-mentioned GDMS, and the Ir concentration was 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 301>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 11 mass% Rh, but otherwise an ingot of a beta type Ga ₂ O ₃ single crystal was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of the sample 101. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of the sample 301 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 301 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 301 was 14 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 302>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 11 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 102. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 302 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 302 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 302 was 21 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 303>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , the side wall portion 5a having a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was a Pt-Rh alloy containing 11 mass% Rh, and an ingot of a beta type Ga ₂ O ₃ single crystal was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of the sample 103. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of the sample 303 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 303 was 101.6 mm and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 303 was 19 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 304>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 11 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 104. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 304 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 304 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 304 was 18 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 305>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 11 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 105. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 305 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 305 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 305 was 24 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 306>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 10 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 106. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 306 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 306 was 101.6 mm and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 306 was 22 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 307>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and the side wall portion 5a having a thickness of 9 mm and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 were Pt-Rh alloy containing 10 mass% Rh, and an ingot of a beta type Ga ₂ O ₃ single crystal was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 107. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 307 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 307 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 307 was 25 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 308>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 10 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 108. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 308 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 308 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 308 was 17 mass ppm in the above-mentioned GDMS, and the Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS. Regarding the crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

<Sample 309>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 10 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 109. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 309 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 309 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 309 was 21 mass ppm in the above-mentioned GDMS, and the _Ir concentration was less than 0.01 mass ppm in the above-mentioned GDMS.

<Sample 310>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , the side wall portion 5a having a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was a Pt-Rh alloy containing 10 mass% Rh, except that an ingot of a beta type Ga ₂ O ₃ single crystal was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of the sample 110. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of the sample 310 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of the sample 310 was 101.6 mm, and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of the sample 310 was 26 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.01 mass ppm in the above-mentioned GDMS.

<Sample 311>
In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO ₂ with a purity of 86.2 mass% containing 13.8 mass% Y ₂ O ₃ , and had a side wall 5a with a thickness of 9 mm, and the composition of the sprayed film 5b covering the inner peripheral surface side of the side wall 5a of the crucible 5 was a Pt-Rh alloy containing 10 mass% Rh, but otherwise a beta type Ga ₂ O ₃ single crystal ingot was obtained in the same manner as the method for obtaining the beta type Ga ₂ O ₃ single crystal substrate of sample 111. The crystal outer diameter of the beta type Ga ₂ O ₃ single crystal was 105.8 mm. Furthermore, a beta type Ga ₂ O ₃ single crystal substrate of sample 311 was obtained from the beta type Ga ₂ O ₃ single crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 311 was 101.6 mm and the thickness was 650 _{μm. The Rh concentration in the beta type Ga2O3 single crystal} substrate of sample 311 was 14 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 312>
A beta type _{Ga2O3 single} crystal ingot was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample _311. The crystal outer diameter of the beta type _{Ga2O3 single} crystal was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 312 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _Ga2O3 single crystal substrate of sample 312 was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 312 was 13 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

<Sample 313>
In the preparation step, a crucible was prepared in which the inner peripheral surface side of the side wall portion 5a was covered with a sprayed film consisting of the following first film 5b1 and second film 5b2, and an ingot of a beta type _{Ga2O3 single} crystal was obtained in the same manner as the method for obtaining the beta type _{Ga2O3 single} crystal substrate of sample 309. That is, in the preparation step of this test example, a first spray material was sprayed on the surface on the inner peripheral surface side of the side wall portion 5a of the crucible 5, thereby covering the surface with a first film 5b1 made of Rh, having a first film porosity of 30%, and having a thickness of 50 μm. Furthermore, a second spray material was sprayed on the first film 5b1, thereby covering the first film 5b1 with a second film 5b2 made of Pt, having a second film porosity of 30%, and having a thickness of 150 μm.

The outer crystal diameter of the beta type _{Ga2O3 single} crystal obtained in this way was 105.8 mm. Furthermore, a beta type _{Ga2O3 single} crystal substrate of sample 313 was obtained from the beta type _{Ga2O3 single} crystal. The diameter of the beta type _{Ga2O3 single} crystal substrate of sample 313 was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta type _{Ga2O3 single} crystal substrate of sample 313 was less than 0.01 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

Tables _{1, 2} , and ₃ show the configurations of the crucibles (inner diameter, composition, surface roughness Rz of the straight body, thickness of the side wall, composition, porosity, thickness, etc. of the sprayed film) used to manufacture the beta-type Ga2O3 single crystal substrates of Samples 10A to 10C, Samples 101 to 115, Samples 20A to 20C, Samples 201 to 213, and Samples 301 to 313. In Tables 1 to 3, when the sprayed film is a single layer, its composition, porosity, and thickness are shown in the column "sprayed film (innermost layer; second film)".

〔evaluation〕
<Product Yield>
The product yield was obtained by the following method for the beta type _{Ga2O3 single} crystals for obtaining the beta type _{Ga2O3 single} crystal substrates of Samples 10B to 10C, Samples 101 to 115, Sample 20C, Samples 201 to 213, and Samples 301 to 313. As described above, the "product yield" means the ratio of the mass of the ingot of the beta type _{Ga2O3 single} crystal grown in the crucible, excluding the region where the crucible breaks or chips or the crystal breaks or chips during cooling, and where the desired diameter cannot be obtained when processed into a beta type gallium trioxide single crystal substrate, and which is evaluated as being a good product as the substrate by the evaluation method described later. The better the product yield of the single crystal, the less likely it is that cracks, chips, etc. occurred in the crucible in which the single crystal was grown.

First, from the beta type _{Ga2O3 single} crystal ingot of each sample taken out of the crucible, a disk-shaped measurement sample (thickness: 1 mm) having a main surface of the (001) plane was cut out and prepared at the measurement points 1 and 2, which are the positions for measuring the crystal outer diameter described above. Furthermore, the main surface of the measurement sample was polished and etched with molten potassium hydroxide as known in the art.

Next, the entire surface of the measurement sample was observed with a differential interference microscope (product name (model number): "LV-150", manufactured by Nikon Corporation), and the number of crystal defects that appeared in one visual field of the differential interference microscope was counted for each visual field, and it was determined whether or not the sample was polycrystallized. In this case, the observation with the differential interference microscope was performed at a magnification of 10 times. As a result, one visual field of the differential interference microscope was 10 mm x 10 mm in size, and the number of crystal defects per visual field was calculated as the density (cm ^-2 ). The crystal defects refer to "etch pits" that appear as corrosion holes on the main surface due to the etching. Although the etch pits are not academically synonymous with dislocations, they can be regarded as equivalent to dislocations in this technical field. Furthermore, the "dislocations" refer to "threading dislocations" that exist inside a beta-type Ga ₂ O ₃ single crystal, and the threading dislocations are known as one type of crystal defect.

　Next, if no polycrystallization was observed in the measurement sample, the measurement sample was evaluated as good. On the other hand, if at least polycrystallization was observed in the measurement sample, the measurement sample was evaluated as defective. For the ingot from which the measurement sample evaluated as defective was cut, a new measurement sample was cut at a position 10 mm toward the measurement point 3 from the measurement point 1 or measurement point 2 from which the measurement sample was cut, and the above-mentioned observation was performed on the new measurement sample using the differential interference microscope. This operation was repeated until the measurement sample was judged to be good.

Finally, the volume of the ingot was calculated from the length (height) of the ingot sandwiched between the cut-out positions of the measurement samples judged to be good and the diameter of the beta-type _{Ga2O3 single} crystal substrate of each sample (i.e., 101.6 mm or 152.4 mm), and the mass of the ingot that could become a product (hereinafter also referred to as "good mass") was calculated from the volume. Next, the ratio of the good mass to the mass of the region sandwiched between the measurement points 1 and 2 of the ingot was calculated, and this was taken as the "product yield". The results are shown in Tables 4, 5, and 6.

[Measurement of activation rate]
The carrier concentration in each sample was obtained by carrying out the above-mentioned measurement method on the beta type _{Ga2O3 single} crystal substrate of Samples 10B to 10C, Samples 101 to 115, Sample 20C, Samples 201 to 213, and Samples 301 to ₃₁₃ , which were prepared using the center part of the substrate. In addition, the impurity concentration of Sn or Si in the beta type _Ga2O3 single crystal substrate was obtained by using glow discharge mass spectrometry (GDMS). The activation rate in each sample was calculated by dividing the carrier concentration in each sample by the impurity concentration obtained by GDMS. The results are shown in Tables 4, 5, and 6.

[Measurement of transmittance]
The transmittance of light having a wavelength of 427 nm in each sample was obtained by carrying out the above-mentioned measurement method on the transmittance measurement samples prepared using the central parts of the beta type Ga ₂ O ₃ single crystal substrates of Samples 10B to 10C, Samples 101 to 115, Sample 20C, Samples 201 to 213, and Samples 301 to 313. The results are shown in Tables 4, 5, and 6.

[Considerations]
According to Table 4, the product yield of the beta type Ga ₂ O ₃ single crystal substrates of Samples 101 to 115 was better than that of the beta type Ga ₂ O ₃ single crystal substrates of Samples 10B to 10C. Therefore, it can be evaluated that the crucible for manufacturing the beta type Ga ₂ O ₃ single crystal substrates of Samples 101 to 115 can suppress the occurrence of cracks and chips during crystal growth compared to that for manufacturing the beta type Ga ₂ O ₃ single crystal substrates of Samples 10B to 10C. According to Table 5, the product yield of the beta type Ga ₂ O ₃ single crystal substrates of Samples 201 to 213 was better than that of the beta type Ga ₂ O ₃ single crystal substrate of Sample 20C. Therefore, it can be evaluated that the crucible for manufacturing _the beta type _Ga2O3 single crystal substrate of Samples 201 to 213 can suppress the occurrence of cracks and chips during crystal growth, compared with that for manufacturing the beta type _Ga2O3 single crystal substrate of Sample 10C. According to Table 6, the product yield of the beta type _{Ga2O3 single} crystal substrate of Samples 301 to 313 was good, similar to that of the beta type _{Ga2O3 single crystal substrate of Samples 101 to 115. Therefore, it can be evaluated that the crucible for manufacturing the beta type Ga2O3 single crystal substrate of} Samples 301 to 313 can suppress the occurrence of cracks and chips during crystal growth.

In particular _, the beta type _{Ga2O3 single} crystal substrates of Samples 113 to 115, Samples 211 to 213, and Sample 313 were superior in activation rate and transmittance compared to the other samples. Therefore, it is evaluated that the beta type _Ga2O3 single crystal substrates of Samples ₁₁₃ to 115, Samples 211 to ₂₁₃ , and Sample 313 can be provided as compound semiconductor substrates excellent in both electrical and optical properties.

Although the embodiments and examples of the present disclosure have been described above, it is also planned from the beginning to combine the configurations of the above-mentioned embodiments and examples as appropriate.

The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope.

100 Single crystal growth apparatus, 5 crucible, 51 seed crystal accommodation section, 52 diameter increase section, 53 straight body section, 5a side wall section, 5b sprayed film, 5b1 first film, 5b2 second film, 5c hole, 6 crucible holder, 7 heating device, 8a seed crystal, 81 beta type Ga ₂ O ₃ single crystal, 82 digallium trioxide melt (Ga ₂ O ₃ melt), 9 sealed container, 1 beta type digallium trioxide single crystal substrate (beta type Ga ₂ O ₃ single crystal substrate), 10 main surface, 10a rectangular slice, O center, OF orientation flat, 21 electrode, S100 beta type Ga ₂ O ₃ single crystal manufacturing process, S110 preparation process, S120 raw material accommodation process, S130 Raw material melting step, S140 _{Ga2O3 single} crystal growth step, S200 beta type _{Ga2O3 single} crystal substrate manufacturing step.

Claims (12)

A crucible for growing beta-type gallium trioxide single crystals, comprising:
The crucible has a thickness of 1 mm or more and 10 mm or less,
The maximum inner diameter of the crucible is 100 mm or more;
The composition of the crucible is stabilized zirconia containing both or either one of yttrium oxide and calcium oxide,
The surface of the crucible on the inner peripheral surface side is coated with a thermal spray film containing both or either one of rhodium and platinum,
The thickness of the thermal spray coating is 100 μm or more and 500 μm or less,
The stabilized zirconia contains at least the yttrium oxide in an amount of 12.0 mass% or more and 15.5 mass% or less, or contains the calcium oxide in an amount of 10.2 mass% or more and 11.4 mass% or less. The crucible according to claim 1, wherein the sprayed film is made of a platinum-rhodium alloy containing 10% by mass or more and 30% by mass or less of rhodium. The thermal sprayed film has pores,
3. The crucible according to claim 2, wherein a porosity, which is a volume ratio of the pores in the thermal sprayed film, is 30 volume % or more and 50 volume % or less. The surface roughness Rz of the surface is 300 μm or more and 500 μm or less,
The thermal sprayed film has pores,
The crucible according to claim 2 , wherein a porosity, which is a volume ratio of the pores in the thermal sprayed film, is 10 volume % or more and less than 30 volume %. The crucible according to claim 3, wherein the surface roughness Rz of the surface is 300 μm or more and 500 μm or less. the thermal spray coating comprises a first coating and a second coating,
the first film covers the surface;
the first film is made of rhodium or a platinum-rhodium alloy containing rhodium as a main component;
the second film covers the first film;
the second film is made of platinum or a platinum-rhodium alloy containing platinum as a main component;
2. The crucible according to claim 1, wherein the total thickness of the sprayed film, including the first film and the second film, is 100 μm or more and 500 μm or less. the first film and the second film both have pores;
The crucible according to claim 6, wherein a first membrane porosity, which is the volume ratio of the pores in the first membrane, and a second membrane porosity, which is the volume ratio of the pores in the second membrane, are both 30 volume % or more and 50 volume % or less. The surface roughness Rz of the surface is 300 μm or more and 500 μm or less,
the first film and the second film both have pores;
The crucible according to claim 6, wherein a first membrane porosity, which is the volume ratio of the pores in the first membrane, and a second membrane porosity, which is the volume ratio of the pores in the second membrane, are both 10 volume % or more and less than 30 volume %. The crucible according to claim 7, wherein the surface roughness Rz of the surface is 300 μm or more and 500 μm or less. A method for producing a beta-type gallium trioxide single crystal substrate using the crucible according to any one of claims 1 to 9,
Providing the crucible;
obtaining a beta-type gallium trioxide single crystal by a vertical boat method using the crucible;
and processing the beta-type gallium trioxide single crystal to obtain a beta-type gallium trioxide single crystal substrate having a circular main surface. A beta-type gallium trioxide single crystal substrate having a circular main surface,
The diameter of the beta-type gallium trioxide single crystal substrate is 100 mm or more;
The main surface is
a (001) plane of a beta-type gallium trioxide single crystal, or a plane having an off-angle of more than 0° and not more than 10° from the (001) plane of the beta-type gallium trioxide single crystal, and an off-direction in the [010] direction of the beta-type gallium trioxide single crystal or in a direction perpendicular to the [010] direction,
The beta-type gallium trioxide single crystal substrate contains both or either one of rhodium and iridium,
A beta-type gallium trioxide single crystal substrate, wherein the rhodium concentration and the iridium concentration are both less than 3 ppm by mass as measured by glow discharge mass spectrometry. The transmittance for light having a wavelength of 400 nm or more and 430 nm or less is 70% or more,
12. The beta type digallium trioxide single crystal substrate according to claim 11, wherein the carrier concentration measured at 25° C. in a Hall measurement by the Van der Pauw method is equal to or more than 1×10 ¹⁷ cm ⁻³ and equal to or less than 1.0×10 ¹⁹ cm ⁻³ .

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