Patent ID: 7535082

Claim:
A gallium nitride wafer characterized in that the gallium nitride wafer is freestanding without being supported by other material substrate, having: a circular shape of a diameter larger than 45 mm; a top surface of Ga-plane (0001) on which crystal films are epitaxially grown; a bottom surface of N-plane (000-1); a multi-mode distortion having a plurality of maxima and a plurality of minima in which the largest value Hm of heights of the maxima is less than 12 μm with the minima in contact with a flat plane; a polished (0001) top surface of roughness satisfying 0.1 nm ≦RMS ≦5 nm without unpolished parts; and a polished (000-1) bottom surface of roughness satisfying 0.1 nm ≦RMS ≦5000 nm without unpolished parts.