| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor wafer and a heterobipolar transistor, using the wafer capable of suppressing degradation of current gain and enhancing reliability, even when carrier concentration is enhanced in a sub-collector layer. SOLUTION: A sub-collector layer 31, a base layer 33 and emitter layers 34, 35 are formed on a substrate 30. Carbon (C) which is not less than 5×1017 cm-3 is added. Lowering of current gain can be eliminated, and reliability can be improved in GaAs HBT.
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