Method for fabricating wafer product and method for fabricating gallium nitride based semiconductor optical device

A method for fabricating a wafer product for a gallium nitride based semiconductor optical device, comprising the steps of:

• preparing a gallium oxide substrate;
• forming a laminate body on a primary surface of the gallium oxide substrate, the laminate body comprising Group III nitrides;
• forming an active layer, after forming the laminate body;
• and
• growing a gallium nitride based semiconductor layer on the active layer,
• forming the laminate body comprises:
• placing the gallium oxide substrate in a growth reactor and thereafter growing a Group III nitride buffer layer at a first temperature on the primary surface of the gallium oxide substrate;
• changing a substrate temperature from the first temperature to a second temperature higher than the first temperature, after growing the Group III nitride buffer layer, the second temperature being higher than the first temperature;
• exposing the gallium oxide substrate and the Group III nitride buffer layer to an atmosphere in the growth reactor at the substrate temperature of the second temperature, while supplying hydrogen and nitrogen into the growth reactor;
• and
• depositing a Group III nitride semiconductor layer for the gallium nitride based semiconductor optical device by a metal-organic vapor phase epitaxy method, after exposing the gallium oxide substrate and the Group III nitride buffer layer to the atmosphere in the growth reactor,
• the Group III nitride semiconductor layer having a first conductivity type,
• the gallium nitride based semiconductor layer having a second conductivity type, and
• a thickness of the Group III nitride buffer layer being smaller than a thickness of the Group III nitride semiconductor layer.