Gallium nitride semiconductor substrate

A gallium nitride substrate with a primary surface for epitaxial growth of a III nitride semiconductor, the gallium nitride substrate, wherein:

• the primary surface has an off-angle, the off-angle being formed by c-axis of the gallium nitride substrate with an axis perpendicular to the primary surface, and the off-angle being less than 2 degrees, and
• a c-face of the gallium nitride substrate is concave or convex, a curvature radius of R of a C-plane of the gallium nitride substrate being equal to or more than 1.5 meters.

A gallium nitride substrate with a primary surface for epitaxial growth of a III nitride semiconductor, the gallium nitride substrate, wherein:

• the primary surface has an off-angle,
• the primary surface has an inner area, an outer area surrounding the inner area, the outer area having at least one of a point or portion in which the off-angle is equal to zero, and
• a c-face of the gallium nitride substrate is concave or convex, a curvature radius of R of a C-plane of the gallium nitride substrate being equal to or more than 1.5 meters.