# Patent

## Title
Method for producing Ga2O3 based crystal film

## Abstract

A Ga2O3 crystal film is epitaxially grown on a Ga2O3 crystal substrate using an MBE method, while controlling the n-type conductivity with high accuracy. Provided is a method for producing a Ga2O3 crystal film, wherein a conductive Ga2O3 crystal film is formed by epitaxial growth using an MBE method. This method for producing a Ga2O3 crystal film comprises a step wherein a Ga2O3 single crystal film containing Sn is grown by producing a Ga vapor and an Sn vapor and supplying the Ga vapor and the Sn vapor to the surface of a Ga2O3 crystal substrate as molecular beams. The Sn vapor is produced by heating Sn oxide that is filled in a cell of an MBE apparatus.

## Background
TECHNICAL FIELD
The invention relates to a method for producing a Ga2O3 based crystal film.
BACKGROUND ART
A method of forming a conductive Ga2O3 crystal film on a crystal substrate such as sapphire substrate by heteroepitaxial growth is known as a conventional method for producing a Ga2O3 based crystal film (see e.g. PTL 1). PTL 1 discloses that a Ga2O3 crystal film is formed using an MBE method and Sn is used as a conductive impurity for imparting conductivity to the Ga2O3 crystal film.
CITATION LIST
Patent Literature
PTL 1
Japanese patent No. 4,083,396
SUMMARY OF INVENTION
Technical Problem
It is an object of the invention to epitaxially grow a Ga2O3 based crystal film on a Ga2O3 based crystal substrate using an MBE method while controlling the n-type conductivity with high accuracy.
Solution to Problem
According to one embodiment of the invention, a method for producing a Ga2O3 based crystal film as defined in [1] to [3] below is provided so as to achieve the above object.
[1] A method for producing a Ga2O3 based crystal film using a MBE method to form a conductive Ga2O3 based crystal film by epitaxial growth, comprising a step of generating Ga vapor and Sn vapor and supplying the Ga vapor and the Sn vapor as a molecular beam to a surface of a Ga2O3 based crystal substrate so as to grow a Ga2O3 based single crystal film comprising Sn,

    
    
        wherein the Sn vapor is generated by heating a Sn oxide that is filled in a cell of an MBE apparatus.
    
    


[2] The method for producing a Ga2O3 based crystal film according to [1], wherein the Sn oxide comprises SnO2, and

    
    
        wherein the Sn vapor is generated at a temperature of the cell of 650° C. to 925° C.
    
    


[3] The method for producing a Ga2O3 based crystal film according to [1] or [2], wherein the Ga2O3 single crystal is epitaxially grown at a growth rate of 0.01 to 100 μm/h.
[4] The method for producing a Ga2O3 based crystal film according to any one of [1] to [3], wherein a carrier concentration of the Ga2O3 based crystal film is 1×1014 to 1×1020/cm3.
[5] The method for producing a Ga2O3 based crystal film according to [1], wherein the Sn oxide comprises SnO2, and

    
    
        wherein the Sn vapor is generated at a temperature of the cell of 450° C. to 1080° C.
    
    


[6] The method for producing a Ga2O3 based crystal film according to [5], wherein the Ga2O3 single crystal is epitaxially grown at a growth rate of 0.01 to 100 μm/h.
[7] The method for producing a Ga2O3 based crystal film according to [5], wherein the Ga2O3 single crystal is epitaxially grown at a growth temperature of 530° C. to 600° C.
Advantageous Effects of Invention
According to one embodiment of the invention, a Ga2O3 based crystal film can be epitaxially grown on a Ga2O3 based crystal substrate using an MBE method while controlling the n-type conductivity with high accuracy.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a vertical cross sectional view showing a Ga2O3 based crystal substrate and a Ga2O3 based crystal film in an embodiment.
FIG. 2 shows a configuration example of an MBE apparatus used for forming the Ga2O3 based crystal film.
FIG. 3 is a graph showing a relation between temperature of a second cell filled with SnO2 and a carrier concentration in the Ga2O3 based crystal film in Example 1.
FIG. 4 is a graph showing a relation between temperature of the second cell filled with SnO2 and a carrier concentration in the Ga2O3 based crystal film in Example 1.
FIG. 5 is a graph showing a relation between temperature of the second cell filled with Si and a carrier concentration in the Ga2O3 based crystal film in Comparative Example.
FIG. 6 is a graph showing a relation between temperature of the second cell filled with SnO2 and a donor concentration in the Ga2O3 based crystal film in Example 2.
FIG. 7 is a graph showing a relation between temperature of the second cell filled with SnO2 and a donor concentration in the Ga2O3 based crystal film in Example 2.



DESCRIPTION OF EMBODIMENTS
Embodiment
As a result of study and investigation, the present inventors found that conductivity is greatly affected by the type of raw material of conductive impurity for imparting conductivity to a Ga2O3 based crystal film when a conductive Ga2O3 based crystal film is epitaxially grown on a substrate formed of a Ga2O3 based crystal, and it is necessary to use a Sn oxide.
A Ga2O3 based crystal film formed on a Ga2O3 based crystal substrate by epitaxial growth can have higher quality than that formed on a substrate having a greatly different crystal structure by heteroepitaxial growth.
In the present embodiment, a highly-conductive Ga2O3 based crystal film is epitaxially grown and formed on a Ga2O3 based crystal substrate by the molecular beam epitaxy (MBE) method using an appropriately selected type of raw material of conductive impurity and heating temperature of the raw material. An example embodiment thereof will be described below.
(Ga2O3 Based Crystal Film)
FIG. 1 is a vertical cross sectional view showing a Ga2O3 based crystal substrate and a Ga2O3 based crystal film in the embodiment.
A Ga2O3 based crystal film 1 is formed by epitaxially growing a Ga2O3 based single crystal on a Ga2O3 based crystal substrate 2 using the MBE method. The MBE method is a crystal growth method in which a raw material used alone or as a compound is heated in an evaporation source called cell and vapor generated by heat is supplied as a molecular beam onto the surface of the substrate to epitaxially grow a crystal.
The Ga2O3 based crystal film 1 is formed of an n-type β-Ga2O3 single crystal containing Sn as a conductive impurity. Here, the β-Ga2O3 based single crystal means a β-Ga2O3 single crystal as well as a β-Ga2O3 single crystal in which a Ga site is substituted by Al, etc. (e.g., a β-(AlxGa1-x)2O3 single crystal (0<x<1)). The Ga2O3 based crystal film 1 has a thickness of, e.g., about 10 to 1000 nm.
The carrier concentration in the Ga2O3 based crystal film 1 is 1×1014 to 1×1020/cm3. This carrier concentration can be controlled by temperature of a second cell 13b of a below-described MBE apparatus 3 during film formation. The second cell 13b is a cell filled with SnO2 as a raw material of Sn which is an impurity for imparting conductivity to the Ga2O3 based crystal film 1.
The Ga2O3 based crystal substrate 2 is formed of a β-Ga2O3 s based ingle crystal of which resistance is increased by adding an impurity such as Mg.
The Ga2O3 based crystal substrate 2 is made by, e.g., the following procedure. Firstly, a semi-insulating β-Ga2O3 single crystal ingot doped with an impurity is made by the EFG method. As the impurity, it is possible to use, e.g., H, Li, Na, K, Rb, Cs, Fr, Be, Ca, Sr, Ba, Ra, Mn, Fe, Co, Ni, Pd, Cu, Ag, Au, Zn, Cd, Hg, Ti or Pb when substituting Ga site. Meanwhile, it is possible to use N or P when substituting oxygen site. For example, for doping Mg, MgO powder is mixed to raw material powder. Not less than 0.05 mol % of MgO is added to impart good insulation properties to the Ga2O3 based crystal substrate 2. Alternatively, the semi-insulating β-Ga2O3 single crystal ingot may be made by the FZ method. The obtained ingot is sliced to a thickness of, e.g., about 1 mm so that the principal surface has a desired plane orientation, thereby forming a substrate. Then, a grinding and polishing process is performed to a thickness of about 300 to 600 μm.
Method for Producing Ga2O3 Based Crystal Film
FIG. 2 shows an example configuration of an MBE apparatus used for forming the Ga2O3 based crystal film. A MBE apparatus 3 is provided with a vacuum chamber 10, a substrate holder 11 supported in the vacuum chamber 10 to hold the Ga2O3 based crystal substrate 2, heating devices 12 held on the substrate holder 11 to heat the Ga2O3 based crystal substrate 2, plural cells 13 (13a, 13b, 13c) filled with raw materials of atoms constituting the Ga2O3 based crystal film 1, heaters 14 (14a, 14b, 14c) for hearing the cells 13, a gas supply pipe 15 for supplying oxygen-based gas into the vacuum chamber 10, and a vacuum pump 16 for exhausting the air in the vacuum chamber 10. It is configured that the substrate holder 11 can be rotated by a non-illustrated motor via a shaft 110.
The first cell 13a is filled with a Ga raw material of the Ga2O3 based crystal film 1, such as Ga powder. The Ga powder desirably has a purity of not less than 6N. The second cell 13b is filled with the Sn oxide (SnO2 or SnO) powder which is a Sn raw material to be doped as a donor to the Ga2O3 based crystal film 1. The Sn oxide may not be in the form of powder. The third cell 13c is filled with, e.g., an Al raw material which is used when the Ga2O3 based crystal film 1 is formed of a β-(AlxGa1-x)2O3 single crystal. A shutter is provided at an opening of each of the first cell 13a, the second cell 13b and the third cell 13c. 
Firstly, the preliminarily-formed Ga2O3 based crystal substrate 2 is attached to the substrate holder 11 of the MBE apparatus 3. Next, the vacuum pump 16 is activated to reduce atmospheric pressure in the vacuum chamber 10 to about 1×10−8 Pa. Then, the Ga2O3 based crystal substrate 2 is heated by the heating devices 12. Here, radiation heat of heat source such as graphite heater of the heating device 12 is thermally transferred to the Ga2O3 based crystal substrate 2 via the substrate holder 11 and the Ga2O3 based crystal substrate 2 is thereby heated.
After the Ga2O3 based crystal substrate 2 is heated to a predetermined temperature, oxygen-based gas such as oxygen radical is supplied into the vacuum chamber 10 through the gas supply pipe 15. Partial pressure of the oxygen-based gas is, e.g., 5×10−4 Pa.
After a period of time required for stabilization of gas pressure in the vacuum chamber 10 (e.g., after 5 minutes), the first cell 13a, the second cell 13b and, if necessary, the third cell 13c are heated by the first heater 14a, the second heater 14b and the third heater 14c, respectively, while rotating the substrate holder 11 so that Ga, Sn and Al are evaporated and are radiated as molecular beam onto the surface of the Ga2O3 based crystal substrate 2.
For example, the first cell 13a is heated to 900° C. and beam-equivalent pressure (BEP) of Ga vapor is 2×10−4 Pa. The second cell 13b filled with SnO2 is heated to 650 to 925° C., and beam-equivalent pressure of Sn vapor varies depending on the temperature of the second cell 13b. 
As such, the β-Ga2O3 based single crystal is epitaxially grown on the Ga2O3 based crystal substrate 2 while being doped with Sn and the Ga2O3 based crystal film 1 is thereby formed.
Here, a growth temperature and a growth rate of the β-Ga2O3 based single crystal are, e.g., respectively 700° C. and 0.01 to 100 μm/h.
The carrier concentration in the Ga2O3 based crystal film 1 is 1×1014 to 1×1020/cm3 and is controlled by the temperature of the second cell 13b. 
Effects of the Embodiment
According to the present embodiment, it is possible to form a highly-conductive Ga2O3 based crystal film on a Ga2O3 based crystal substrate by epitaxial growth using the MBE method. It is possible to use the formed Ga2O3 based crystal film as components of semiconductor elements such as Ga2O3 based light-emitting devices or transistors.
The invention is not intended to be limited to the above-mentioned embodiment, and the various kinds of modifications can be implemented without departing from the gist of the invention.
EXAMPLES
Example 1
A relation between the temperature of the second cell 13b filled with SnO2 powder and the carrier concentration in the Ga2O3 crystal film 1 was obtained by experiment.
In the present Example, a substrate formed of a high-resistance β-Ga2O3 single crystal doped with 0.25 mol % of Mg was used as the Ga2O3 based crystal substrate 2. Meanwhile, a film of a β-Ga2O3 single crystal was formed as the Ga2O3 based crystal film 1. The principal surface of the Ga2O3 based crystal substrate was a (010) plane. The plane orientation of the substrate is not specifically limited but the principal surface of the Ga2O3 based crystal substrate is preferably a plane rotated by not less than 50° and not more than 90° with respect to a (100) plane. In other words, on the Ga2O3 based substrate, an angle θ (0<θ≦90°) formed between the principal surface and the (100) plane is preferably not less than 50°. Examples of the plane rotated by not less than 50° and not more than 90° with respect the (100) plane include a (010) plane, a (001) plane, a (−201) plane, a (101) plane and a (310) plane.
In addition, during the film formation of the Ga2O3 based crystal film 1, partial pressure of the oxygen-based gas was 5×10−4 Pa, the temperature of the first cell 13a was 900° C., beam-equivalent pressure of Ga vapor was 2×10−4 Pa, the growth temperature of the β-Ga2O3 single crystal was 700° C. and the growth rate of the β-Ga2O3 single crystal was 0.7 μm/h.
Various samples were made at different temperatures of the second cell 13b filled with SnO2 in a range of 750 to 850° C. Then, the carrier concentration of each was measured by Hall measurement to obtain a relation between the temperature of the second cell 13b and the collier concentration in the Ga2O3 based crystal film 1.
FIG. 3 is a graph showing a relation between the temperature of the second cell 13b and the carrier concentration in the Ga2O3 based crystal film 1, which was obtained by measurement under the conditions mentioned above. In FIG. 3, the horizontal axis indicates the temperature of the second cell 13b filled with SnO2 powder and the vertical axis indicates the carrier concentration in the Ga2O3 based crystal film 1. FIG. 3 is a semi-log graph in which the vertical axis is plotted on a logarithmic scale.
As shown in FIG. 3, the measured values on the semi-log graph form a substantially straight line which shows that the carrier concentration in the Ga2O3 based crystal film 1 increases with an increase in the temperature of the second cell 13b. 
In addition, when the growth rate of the β-Ga2O3 single crystal is multiplied by n (n is a positive real number), the concentration of SnO2 added to the Ga2O3 based crystal film 1 is 1/n and the carrier concentration is also 1/n. Therefore, as shown in FIG. 4, the relation between the temperature of the second cell 13b and the carrier concentration in the Ga2O3 based crystal film 1 at the growth rate of 0.01 to 100 μm/h can be obtained based on the relation at the growth rate of 0.7 μm/h.
Here, 0.01 to 100 μm/h is a growth rate generally used for the β-Ga2O3 single crystal. When the growth rate is 0.01 μm/h, for example, the temperature of the first cell 13a filled with the Ga raw material is 700° C. and partial pressure of the oxygen-based gas is 1×10−5 Pa. Meanwhile, when the growth rate is 100 μm/h, for example, the temperature of the first cell 13a is 1200° C. and partial pressure of the oxygen-based gas is 1×10−1 Pa.
The straight lines in FIG. 4 each indicating the relation between temperature of the second cell 13b and the carrier concentration in the Ga2O3 based crystal film 1 are obtained when the growth rates of the β-Ga2O3 single crystal are 0.01 μm/h, 0.7 μm/h and 100 μm/h.
It is seen from FIG. 4 that the temperature of the second cell 13b filled with SnO2 powder should be 650 to 925° C. in order to obtain a generally-required carrier concentration of 1×1014 to 1×1020/cm3 under the condition at the growth rate of 0.01 to 100 μm/h.
It was also possible to accurately control the n-type conductivity of the Ga2O3 based crystal film in case of using SnO as a Sn raw material even though the temperature range of the second cell 13b was different from that in the case of using SnO2. In other words, it is possible to accurately control the n-type conductivity of the Ga2O3 based crystal film by using the Sn oxide as the Sn raw material.
On the other hand, if Sn instead of the Sn oxide was loaded as the Sn raw material in the second cell 13b to form the Ga2O3 based crystal film 1, it was not possible to obtain the carrier concentration of not less than 1×1014/cm3 regardless of the conditions such as the temperature of the second cell 13b or the growth rate of the β-Ga2O3 single crystal.
Meanwhile, when Si was loaded as a conductive impurity in the second cell 13b instead of the Sn oxide to form the Ga2O3 based crystal film 1, it was not possible to control Si vapor pressure depending on the temperature of the second cell 13b even though the cause is not certain, and it was difficult to highly accurately control the Si amount in the Ga2O3 based crystal film 1. FIG. 5 is a graph showing a relation between the temperature of the second cell 13b filled with Si and the carrier concentration in the Ga2O3 based crystal film 1, which was obtained by experiment. The measurement conditions are the same as the case of using the Sn oxide. As shown in FIG. 5, the carrier concentration in the Ga2O3 based crystal film 1 varies even at the same temperature of the second cell 13b and conductivity is not obtained in some cases. Also, when Si oxide (SiO, SiO2) was used instead of Si, it was not possible to control Si oxide vapor pressure depending on the temperature of the second cell 13b, and furthermore, the n-type conductivity of the Ga2O3 based crystal film 1 was not obtained regardless of the doped amount of Si oxide (even when doped with up to about several mol %).
Example 2
A relation between the temperature of the second cell 13b filled with SnO2 powder and the donor concentration in the Ga2O3 based crystal film 1 was obtained by experiment.
In the present Example, a substrate formed of an n-type β-Ga2O3 single crystal doped with 0.05 mol % of Si was used as the Ga2O3 based crystal substrate 2. Meanwhile, a film of a β-Ga2O3 single crystal was formed as the Ga2O3 based crystal film 1.
The principal surface of the Ga2O3 based crystal substrate was a (010) plane. The plane orientation of the substrate is not specifically limited but the principal surface of the Ga2O3 based crystal substrate is preferably a plane rotated by not less than 50° and not more than 90° with respect to a (100) plane. In other words, on the Ga2O3 based substrate, an angle θ (0<θ≦90°) formed between the principal surface and the (100) plane is preferably not less than 50°. Examples of the plane rotated by not less than 50° and not more than 90° with respect the (100) plane include a (010) plane, a (001) plane, a (−201) plane, a (101) plane and a (310) plane.
During the film formation of the Ga2O3 based crystal film 1, partial pressure of the oxygen-based gas was 5×10−4 Pa, the temperature of the first cell 13a was 900° C., beam-equivalent pressure of Ga vapor was 2×10−4 Pa, the growth temperature of the β-Ga2O3 single crystal was 530° C., 570° C. and 600° C. and the growth rate of the β-Ga2O3 single crystal was 0.7 μm/h.
Various samples were made at different temperatures of the second cell 13b filled with SnO2 in a range of 585 to 820° C. Then, the donor concentration of each was measured by C-V measurement to obtain a relation between the temperature of the second cell 13b and the donor concentration in the Ga2O3 based crystal film 1.
FIG. 6 is a graph showing a relation between the temperature of the second cell 13b and the miler concentration in the Ga2O3 based crystal film 1 (when the growth temperature is set to 530° C., 570° C. and 600°), which was obtained by measurement under the conditions mentioned above. In FIG. 6, the horizontal axis indicates the temperature of the second cell 13b filled with SnO2 powder and the vertical axis indicates the donor concentration in the Ga2O3 based crystal film 1. FIG. 6 is a semi-log graph in which the vertical axis is plotted on a logarithmic scale.
As shown in FIG. 6, the donor concentration in the Ga2O3 based crystal film 1 increases with an increase in the temperature of the second cell 13b. Here, it was found that the amount of SnO2 incorporated into an epi film changes with a change in the growth temperature. In detail, the incorporated amount of SnO2 has a tendency to increase with a decrease in the growth temperature (growth temperature dependence). In this regard, however, the growth temperature dependence decreases at not more than 570° C. In addition, it was also found that the slope of the relation between the SnO2 cell temperature and the donor concentration at the growth temperature of not more than 570° C. coincides with SnO2 vapor pressure curve. It was confirmed that, when the growth temperature is lowered to 500° C., the epi surface becomes rough and a film having low crystal quality is grown. Therefore, the growth temperature (substrate temperature) is set between 530° C. and 600° C., preferably, between 530° C. and 570° C. to allow crystal quality to be maintained during growth.
In addition, when the growth rate of the β-Ga2O3 single crystal is multiplied by n (n is a positive real number), the concentration of SnO2 added to the Ga2O3 based crystal film 1 is 1/n and the donor concentration is also 1/n. Therefore, as shown in FIG. 7, the relation between the temperature of the second cell 13b and the donor concentration in the Ga2O3 based crystal film 1 at the growth rate of 0.01 to 100 μm/h can be obtained based on the relation at the growth rate of 0.7 μm/h.
Here, 0.01 to 100 μm/h is a growth rate generally used for the β-Ga2O3 single crystal. When the growth rate is 0.01 μm/h, for example, the temperature of the first cell 13a filled with the Ga raw material is 700° C. and partial pressure of the oxygen-based gas is 1×10−5 Pa. Meanwhile, when the growth rate is 100 μm/h, for example, the temperature of the first cell 13a is 1200° C. and partial pressure of the oxygen-based gas is 1×10−1 Pa.
FIG. 7 is a graph showing a relation between temperature of the second cell 13b and the donor concentration in the Ga2O3 based crystal film 1 when the respective growth rates of the β-Ga2O3 single crystal are 0.01 μm/h, 0.7 μm/h and 100 μm/h (when the growth temperature is set to 570° C.).
It is seen from FIG. 7 that the temperature of the second cell 13b filled with SnO2 powder should be 450 to 1080° C. in order to obtain a generally-required donor concentration of 1×1014 to 1×1020/cm3 under the condition at the growth rate of 0.01 to 100 μm/h.
Although the experiment was conducted using the β-Ga2O3 single crystal as the Ga2O3 based crystal film 1 in the present Example, substantially the same result is obtained in case of using a β-Ga2O3 single crystal in which a Ga site is substituted by Al, etc.
Although the embodiment and examples of the invention have been described above, the invention according to claims is not to be limited to the above-mentioned embodiment and examples. Further, all combinations of the features described in the embodiment and examples are not necessary to solve the problem of the invention.
INDUSTRIAL APPLICABILITY
It is possible to epitaxially grow a Ga2O3 based crystal film on a Ga2O3 based crystal substrate using an MBE method while controlling the n-type conductivity with high accuracy.
REFERENCE SIGNS LIST


    1 Ga2O3 based crystal film
    2 Ga2O3 based crystal substrate
    3 MBE apparatus
    13b second cell

## Claims

1. A method for producing a Ga2O3 based crystal film using a molecular beam epitaxy (MBE) method to form a conductive Ga2O3 based crystal film by epitaxial growth, the method comprising:
generating Ga vapor and Sn vapor and supplying the Ga vapor and the Sn vapor as a molecular beam to a surface of a Ga2O3 based crystal substrate, while an oxygen-based gas being supplied to a vacuum chamber, so as to grow a Ga2O3 based single crystal film comprising Sn,
wherein the Sn vapor is generated by heating a Sn oxide that is filled in a cell of an MBE apparatus, and
wherein the surface of the Ga2O3 based crystal substrate includes a plane rotated by not less than 50° and not more than 90° with respect to a (100) plane.

2. The method for producing a Ga2O3 based crystal film according to claim 1, wherein the Sn oxide comprises SnO2, and
wherein the Sn vapor is generated at a temperature of the cell of 650° C. to 925° C.

3. The method for producing a Ga2O3 based crystal film according to claim 1, wherein the Ga2O3 based single crystal film is epitaxially grown at a growth rate of 0.01 μm/h to 100 μm/h.

4. The method for producing a Ga2O3 based single crystal film according to claim 1, wherein a carrier concentration of the Ga2O3 based crystal film is 1×1014/cm3 to 1×1020/cm3.

5. The method for producing a Ga2O3 based crystal film according to claim 3, wherein a carrier concentration of the Ga2O3 based single crystal film is 1×1014/cm3 to 1×1020/cm3.

6. The method for producing a Ga2O3 based crystal film according to claim 1, wherein the Sn oxide comprises SnO2, and
wherein the Sn vapor is generated at a temperature of the cell of 450° C. to 1080° C.

7. The method for producing a Ga2O3 based crystal film according to claim 6, wherein the Ga2O3 based single crystal film is epitaxially grown at a growth rate of 0.01 μm/h to 100 μm/h.

8. The method for producing a Ga2O3 based crystal film according to claim 6, wherein the Ga2O3 based single crystal film is epitaxially grown at a growth temperature of 530° C. to 600° C.

9. The method for producing a Ga2O3 based crystal film according to claim 2, wherein the Ga2O3 based single crystal film is epitaxially grown at a growth rate of 0.01 μm/h to 100 μm/h.

10. The method for producing a Ga2O3 based crystal film according to claim 2, wherein a carrier concentration of the Ga2O3 based single crystal film is 1×1014/cm3 to 1×1020/cm3.

11. A method for producing a Ga2O3 based crystal film using a molecular beam epitaxy (MBE) method to form a conductive Ga2O3 based crystal film by epitaxial growth, the method comprising:
generating Ga vapor and Sn vapor and supplying the Ga vapor and the Sn vapor as a molecular beam to a surface of a Ga2O3 based crystal substrate, while an oxygen-based gas being supplied to a vacuum chamber, so as to grow a Ga2O3 based single crystal film comprising Sn,
wherein the Sn vapor is generated by heating a Sn oxide that is filled in a cell of an MBE apparatus,
wherein a growth temperature is set between 530° C. and 570° C., and
wherein an n-type conductivity of the Ga2O3 based single crystal film is controlled by a temperature of the cell.

12. The method for producing a Ga2O3 based crystal film according to claim 1, wherein the Sn oxide comprises SnO2, and
wherein the Ga2O3 based single crystal film is epitaxially grown at a growth rate of 0.01 μm/h to 100 μm/h.

13. The method for producing a Ga2O3 based crystal film according to claim 1, wherein the Sn oxide comprises SnO2, and
wherein a carrier concentration of the Ga2O3 based single crystal film is 1×1014/cm3 to 1×1020/cm3.

14. The method for producing a Ga2O3 based crystal film according to claim 1, wherein the plane rotated by not less than 50° and not more than 90° with respect to the (100) plane includes one of a (010) plane, a (001) plane, a (−201) plane, a (101) plane, and a (310) plane.

15. The method for producing a Ga2O3 based crystal film according to claim 1, wherein an n-type conductivity of the Ga2O3 based single crystal film is controlled by a temperature of the cell.

16. The method for producing a Ga2O3 based crystal film according to claim 1, wherein a conductivity of the Ga2O3 based single crystal film is controlled by a temperature of the cell.

17. The method for producing a Ga2O3 based crystal film according to claim 11, wherein the Sn oxide comprises SnO2, and
wherein the Ga2O3 based single crystal film is epitaxially grown at a growth rate of 0.01 μm/h to 100 μm/h.

18. The method for producing a Ga2O3 based crystal film according to claim 17, wherein the Sn vapor is generated at a temperature of the cell of 450° C. to 1,080° C.

19. The method for producing a Ga2O3 based crystal film according to claim 11, wherein the Sn oxide comprises SnO2, and
wherein a carrier concentration of the Ga2O3 based single crystal film is 1×1014/cm3 to 1×1020/cm3.

20. The method for producing a Ga2O3 based crystal film according to claim 19, wherein the Sn vapor is generated at a temperature of the cell of 450° C. to 1,080° C.