| 摘要 |
PROBLEM TO BE SOLVED: To provide a double heterojunction bipolar transistor having improved high-frequency characteristics in high current injection.SOLUTION: In the double heterojunction bipolar transistor, a sub-collector layer 2, a collector layer, a base layer 4, an emitter layer 5 and a cap layer 6 are sequentially laminated on a substrate 1. The collector layer is formed of a multilayer structure of a first semiconductor layer 31 and a second semiconductor layer 32. The first semiconductor layer 31 and the second semiconductor layer 32 form heterojunction of Type-II. The second semiconductor layer 32 and the base layer 4 form homojunction or heterojunction of Type-I. |
