| 摘要 |
PROBLEM TO BE SOLVED: To sufficiently increase the breakdown voltage and the current gain in a heterobipolar transistor device. SOLUTION: A collector layer 12 composed of n-type gallium nitride, a base layer 13 composed of p-type silicon germanium, and an emitter layer 14 composed of n-type gallium nitride are successively formed on a semiconductor substrate 11 composed of p-type silicon according to selective growth process. Thus, since a valence band energy differenceΔEv between the emitter layer 14 and the base layer 13, and a valence band energy differenceΔEv between the collector layer 12 and the base layer 13 are increased, both the breakdown voltage and the current gain are increased.
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