Patent ID: 8742396

Claim:
A III nitride epitaxial substrate comprising: a substrate; an AlN buffer layer formed on the substrate; a first superlattice laminate and a second superlattice laminate sequentially formed on the buffer layer; and a III nitride laminate having an active layer including an Al α Ga 1-α N (0.03≦α(alpha)) layer epitaxially grown on the second superlattice laminate, wherein: the first superlattice laminate includes a first layer made of Al a Ga 1-a N and a second layer made of Al b Ga 1-b N (0.9≦b≦1) which are alternately stacked, where α(alpha)<a and a<b: hold, and the second superlattice laminate includes repeated layer sets each layer set having a third layer made of Al x Ga 1-x N (0.20≦x≦0.90), a fourth layer made of Al y Ga 1-y N (0.60≦y≦0.95), and a fifth layer made of Al z Ga 1-z N (0.9<z≦1), where α(alpha)<x and x<y<z, and y−x is smaller than z−y, and the bottom most layer of the second superlattice laminate is the third layer.