Patent ID: 6921923

Claim:
A group III nitride compound semiconductor device of a successively laminated structure, comprising: a substrate; a buffer layer formed directly on said substrate and having a buffer layer lattice constant; an intervening layer formed directly on said buffer layer, said intervening layer comprising Al a Ga b In 1-a-b N, where 0<a<1, 0<b<1, and a+b<1; a light-emitting layer formed directly on said intervening layer, said light-emitting layer comprising In Y Ga 1-Y N, where 0<Y<1, and having a light-emitting layer lattice constant; and a p-type clad layer formed directly on said light-emitting layer, wherein said p-type clad layer comprises an ungraded GaN layer, and wherein composition ratios of at least Al and In of said intervening layer change from a first interface with said buffer layer to a second interface with said light-emitting layer, such that, a first lattice constant of said intervening layer at said first interface is lattice-matched to said buffer layer and changes to a second lattice constant at said second interface, which is substantially equal to said light-emitting layer lattice constant.