III-V heterojunction bipolar transistor having a GaAs emitter ballast

摘要

A hetero-junction bipolar transistor having high reliability wherein a ballast resistance is exactly controlled and deterioration in current stability is eliminated. A GaAs ballast resistor layer is provided in a hetero-junction bipolar transistor having a GaAs emitter layer, an InGaP spacer layer, and a GaAs base layer, preventing a notch from being formed in the conduction band at the interface of the emitter layer and the ballast resistor layer, exactly controlling the ballast resistance. The AlGaAs layer is prevented from trapping impurities and the current stability is prevented from deteriorating.