| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-frequency power amplifier capable of operating at low voltage. SOLUTION: On an epitaxial layer 330 for GaAs-HBT formation, n-InGaAs layers 306 and 307 doped with group VI elements are formed with the In composition, varied continuously from 0 to about 0.5 from the lower part in the direction of depth. An epitaxial layer 329 for InP bipolar transistor formation is grown thereon, to form an epitaxial wafer. The wafer is utilized to form an RF transistor comprising a high-frequency power amplifier circuit, using GaAs- HBT and a bipolar transistor for a DC base bias circuit also comprising the high-frequency power amplifier circuit, using an InP substance having a narrow- band gap. Thus a power amplifier circuit is formed on a single chip, the power amplifier circuit of which enables maintaining proper high-frequency characteristics of GaAs-HBT and further cope with shift for lowing the voltage.
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