| 摘要 |
PROBLEM TO BE SOLVED: To provide a double heterojunction bipolar transistor which is small in the transient build-up voltage of a collector current, wherein the power efficiency when it is used, for example, for a high-frequency power amplifier, can be improved. SOLUTION: There are provided a first semiconductor layer (11), which is formed on a semiconductor substrate and contains a first conductivity-type impurity of high concentration as a sub-collector, a second semiconductor layer (12), which is formed on the first semiconductor layer, and contains a first conductivity-type impurity of low concentration as a collector, a third semiconductor layer (13) which is formed on the second semiconductor layer, a fourth semiconductor layer (14) which is formed on the third semiconductor layer, and contains a second conductivity-type impurity of high concentration as a base, and a fifth semiconductor layer (15) which is formed on the fourth semiconductor layer, contains the first conductivity-type impurity as an emitter, and has forbidden band width larger than that of the fourth semiconductor layer. The third semiconductor layer has forbidden band width larger than that of the fourth semiconductor layer and spontaneous polarization. COPYRIGHT: (C)2004,JPO
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