Composite substrate, method for producing composite substrate, and method for producing gallium oxide crystal film
A composite substrate includes: a base substrate and an α-Ga 2 O 3 crystal film that is provided on the base substrate, has a thickness of 10 μm or more, and has at least one alkali metal element content of 1.2×10 15 atoms/cm 3 or more and 1.0×10 18 atoms/cm 3 or less.
1 . A composite substrate comprising:
a base substrate and
an α-Ga 2 O 3 crystal film that is provided on the base substrate, has a thickness of 10 μm or more, and has at least one alkali metal element content of 1.2×10 15 atoms/cm 3 or more and 1.0×10 18 atoms/cm 3 or less.
2 . The composite substrate according to claim 1 , wherein the base substrate is an α-Cr 2 O 3 substrate.
3 . The composite substrate according to claim 1 , wherein
the crystal orientation differences between the α-Ga 2 O 3 crystal film and the base substrate with respect to their (0001) plane and (10-10) plane are both 0.4 degrees or less.
4 . The composite substrate according to claim 1 , wherein
the α-Ga 2 O 3 crystal film has an X-ray rocking curve half-width of 2000 arcsec or less on a (006) plane and a (104) plane.
5 . The composite substrate according to claim 1 , wherein
at least one of a Cr content and a Ni content of the α-Ga 2 O 3 crystal film is 2.0×10 15 atoms/cm 3 or more and 1.0×10 17 atoms/cm 3 or less.
6 . The composite substrate according to claim 1 , wherein
a Li content, a Na content, and a K content of the α-Ga 2 O 3 crystal film are individually 1.2×10 15 atoms/cm 3 or more and 1.0×10 18 atoms/cm 3 or less.
7 . A method for producing the composite substrate according to claim 1 , wherein
the α-Ga 2 O 3 crystal film is formed on a surface of the base substrate by bringing the base substrate into a supercritical state at a temperature of 390° C. or more and at a pressure of 22.1 MPa or more while the base substrate is immersed in an aqueous solution containing Ga ions.
8 . The method for producing a composite substrate according to claim 7 , wherein
the aqueous solution contains an alkali metal element.
9 . A method for producing a gallium oxide crystal film, comprising
removing the base substrate from the composite substrate according to claim 1 to prepare a free-standing α-Ga 2 O 3 crystal film.
10 . A method for producing a gallium oxide crystal film, comprising
removing the base substrate from the composite substrate produced by the method for producing a composite substrate according to claim 7 to prepare a free-standing α-Ga 2 O 3 crystal film.