Patent ID: 7525128

Claim:
A light-emitting zinc oxide-based compound semiconductor device having a double-heterostructure comprising: a light-emitting layer having first and second major surfaces and formed of a single layer of low-resistivity Mg 1−x−y Cd x Zn y O; 0<x<1, 0<y<1, and x+y=0.1 to 1, compound semiconductor doped with an impurity; a first clad layer joined to said first major surface of said light-emitting layer and formed of an n-type zinc oxide-based compound semiconductor having a composition different from that of said compound semiconductor of said light-emitting layer; and a second clad layer joined to said second major surface of said light-emitting layer and formed of a low-resistivity p-type zinc oxide-based compound semiconductor having a composition different from that of said compound semiconductor of said light-emitting layer; a first contact layer joined to the first clad layer, the first contact layer composed of an n-type zinc oxide-based compound semiconductor having a higher concentration of n-type impurity than the first clad layer; a second contact layer joined to the second clad layer, the second contact layer composed of a p-type zinc oxide-based compound semiconductor having a higher concentration of p-type impurity than the second clad layer; a buffer layer composed of a zinc oxide layer and joined to the first contact layer, the buffer layer having relatively high crystallinity; and a substrate composed of zinc oxide joined to the buffer layer, the substrate sufficiently thick to provide structural support for the light-emitting layer, the first and second clad layers, the first and second contact layers and the buffer layer.