Patent ID: 7097920

Claim:
A self-supporting substrate of group III nitride based semiconductor; wherein the self-supporting substrate is formed by growing a layer of group III nitride based semiconductor on a substrate of a different material and thereafter removing the substrate of the different material; and wherein the self-supporting substrate has a surface of a front side and a surface of a rear side; a dislocation density for the surface of the front side and a dislocation density for the surface of the rear side are different from one another; and on comparison between the dislocation density for the surface of the front side and the dislocation density for the surface of the rear side, when a lower dislocation density selected from the dislocation density for the surface of the front side or the dislocation density for the surface of the rear side is designated n 1 , and a higher dislocation density selected from the dislocation density for the surface of the front side or the dislocation density for the surface of the rear side is designated n 2 , a ratio of n 2 /n 1 is 250 or less.