HETEROJUNCTION BIPOLAR TRANSISTOR, POWER AMPLIFIER USING THE SAME, AND METHOD OF MANUFACTURING HETEROJUNCTION BIPOLAR TRANSISTOR

摘要

PROBLEM TO BE SOLVED: To combine prevention of thermorunaway and prevention of degradation in power amplifier characteristics at high temperature.SOLUTION: A heterojunction bipolar transistor 100 comprises a ballast resistance layer 7. The ballast resistance layer 7 comprises: an AlGaAs emitter ballast resistance layer 7a having a positive resistivity temperature coefficient in a first temperature range (room temperature-100°C) and a second temperature range (100°C or more); and an AlGaAs emitter ballast resistance layer 7b having a positive resistivity temperature coefficient in the second temperature range.