A Group III-V compound semiconductor includes, at least, a substrate, a
buffer layer of the general formula In.sub.uGa.sub.vAl.sub.wN (wherein,
0.ltoreq.u.ltoreq.1, 0.ltoreq.v.ltoreq.1, 0.ltoreq.w.ltoreq.1, u+v+w=1)
and a Group III-V compound semiconductor crystal layer of the general
formula In.sub.xGa.sub.yAl.sub.zN (wherein, 0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1, x+y+z=1), in this order,
wherein the buffer layer has a thickness of at least about 5 .ANG. and
not more than about 90 .ANG.. A method is provided for producing the
Group III-V compound semiconductor, including forming a buffer layer of
the general formula In.sub.uGa.sub.vAl.sub.wN on a substrate to give a
thickness of at least about 5 .ANG. and not more than about 90 .ANG. at
temperatures lower than the growing temperature of the compound
semiconductor crystal layer before growing the compound semiconductor
crystal layer, and then growing a Group III-V compound semiconductor
crystal layer of the general formula In.sub.xGa.sub.yAl.sub.zN on the
buffer layer.