Patent ID: 7786488

Claim:
A nitride semiconductor wafer characterized in that the nitride semiconductor 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 total thickness variation (TTV) less than 10 μm which is measured at sampling points defined at an interval 0.1 mm on the wafer; a (0001) top surface of roughness satisfying 0.1 nm≦RMS≦5 nm without unpolished parts; and a (000-1) bottom surface of roughness satisfying 0.1 nm≦RMS≦5000 nm without unpolished parts, wherein the wafer has a multi-mode distortion having a plurality of maxima and a plurality of minima in which the largest values Hm of heights of the maxima is less than 12 μm with the minima in contact with a flat plane.