Patent ID: 8395237

Claim:
A bipolar transistor comprising: a substrate; a collector layer configured to be formed above said substrate and include a first nitride semiconductor; a base layer with a p-conductive-type, configured to be formed on said collector layer and include a second nitride semiconductor; and an emitter layer with an n-conductive-type, configured to be formed on said base layer and include a third nitride semiconductor, wherein said collector layer, said base layer and the emitter layer are formed so that crystal growing directions with respect to a surface of said substrate are in parallel to a [ 0001 ] direction of said substrate, wherein said first nitride semiconductor includes: In yc Al xc Ga 1-xc-yc N (0≦xc≦1, 0≦yc≦1, 0<xc+yc≦1), and wherein, in said first nitride semiconductor, a length of an a-axis on a surface side is longer than a length of an a-axis on a substrate side.