Patent ID: 8441034

Claim:
An epitaxial substrate comprising: a gallium nitride substrate of single crystal gallium nitride including a primary surface, the primary surface having a first area and a second area, an off-angle formed by a c-axis of the gallium nitride substrate with an axis perpendicular to the primary surface being greater than zero over the first and second areas, and a c-face of the single crystal gallium nitride of the gallium nitride substrate being concave or convex, a curvature radius R of a C-plane of the single crystal gallium nitride of the gallium nitride substrate being equal to or more than 1.5 meters; and a III nitride semiconductor film formed on the gallium nitride substrate, the III nitride semiconductor film including a primary surface, the primary surface of the III nitride semiconductor film including a surface morphology, and the surface morphology including no six-sided pyramid pattern.