Patent ID: 8143140

Claim:
A method of producing a thin GaN film-joined substrate, the method comprising the steps of: joining on a GaN bulk crystalline body a substrate different in type, different in chemical composition from GaN; and dividing said GaN bulk crystalline body at a plane having a distance of at least 0.1 μm and at most 100 μm from an interface thereof with said substrate different in type, to provide a thin film of GaN on said substrate different in type, wherein said GaN bulk crystalline body had a surface joined to said substrate different in type, that has a maximum surface roughness Rmax of at most 20 μm, and an off-angle formed by said surface of said GaN bulk crystalline body to be joined and a (0001) plane of said GaN bulk crystalline body is at least 0.03° and at most 20°.