| 摘要 |
A bipolar transistor includes: a substrate; a collector and a base layer with a p-conductive-type, an emitter layer with an n-conductive-type. The collector layer is formed above the substrate and includes a first nitride semiconductor. The base layer with the p-conductive-type is formed on the collector layer and includes a second nit ride semiconductor. The emitter layer with the n-conductive-type is formed on the base layer and includes a third nitride semiconductor. The collector layer, the base layer and the emitter layer are formed so that crystal growing directions with respect to a surface of the substrate are in parallel to a [0001] direction of the substrate. The first nitride semiconductor includes: InycAlxcGa1-xc-ycN (0≦̸xc≦̸1, 0≦̸yc≦̸1, 0<xc+yc≦̸1). In the 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.
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