Patent ID: 7915640

Claim:
A heterojunction semiconductor device comprising: a substrate; a metamorphic buffer layer on said substrate; an active layer on said metamorphic buffer layer, the active layer including a collector layer; and an electrode on said metamorphic buffer layer, wherein, said metamorphic buffer layer comprises indium-gallium-arsenic In x Ga 1-x As in which 0≦x≦1, part of said metamorphic buffer layer is between the collector layer and the substrate, the part being in contact with both the collector layer and the substrate, at least a portion of said metamorphic buffer layer in contact with said active layer contains an impurity introduced therein in a high concentration of at least 1×10 19 /cm 3 , and the impurity is not introduced into a region of said metamorphic buffer layer in which a concentration of indium is such that x≅0.