Patent ID: 8679955

Claim:
A method for forming an epitaxial wafer, comprising the steps of: placing a gallium oxide substrate in a growth reactor; changing a substrate temperature of the gallium oxide substrate, while supplying nitrogen into the growth reactor so as to expose the gallium oxide substrate to a nitrogen atmosphere; after the substrate temperature reaches a first film formation temperature, forming a buffer layer of Al X Ga 1-X N (0<x≦1) at the first film formation temperature, while supplying nitrogen into the growth reactor; and growing a gallium nitride based semiconductor epitaxial layer on the buffer layer at a second film formation temperature in the growth reactor, the first film formation temperature being not less than 550 Celsius degrees, and supply of hydrogen into the growth reactor being started during growth of the buffer layer, wherein a thickness of the buffer layer is not less than 2 nm, wherein a maximum temperature in the step of changing a substrate temperature of the gallium oxide substrate is not less than 550 Celsius degrees and not more than the first film formation temperature, and wherein the step of changing a substrate temperature of the gallium oxide substrate includes the steps of: changing the substrate temperature to a pretreatment temperature of not more than the first film formation temperature and not less than 550 Celsius degrees, in a nitrogen atmosphere; and after the substrate temperature reaches the pretreatment temperature, placing the gallium oxide substrate in the nitrogen atmosphere for a predetermined duration, while maintaining the substrate temperature.