| 摘要 |
PROBLEM TO BE SOLVED: To provide a heterojunction bipolar transistor of a structure, wherein a leakage current in a base layer due to the recombination between an emitter layer and an emitter cap layer is reduced and a current gain can be increased. SOLUTION: In a heterojunction bipolar transistor, which uses a III-V compound semiconductor substrate and is formed by laminating in order at least a base layer 5, an emitter layer 4 formed of a material having an energy gap larger than that of the layer 5 and a cap layer 2 on the semiconductor substrate, a thin film layer 3 added with impurities of a concentration higher than that of the layer 4 is inserted between the above layers 4 and 2.
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