Investigation of an InGaP/GaAs/InGaAs Step-Emitter Bipolar Transistor

A high-performance InGaP/GaAs/InGaAs step-emitter bipolar transistor is demonstrated. The energy bands and carrier distributions are described by theoretical analysis. Because the confinement effect for holes is substantially enhanced by the addition of an InGaAs quantum well between base-emitter junction as compared to the conventional InGaP/GaAs heterojunction bipolar transistor, the experimental device exhibits a high current gain up to 220. In particular, a relatively low collector-emitter offset voltage of 70 mV is observed, attributed to the neglect of potential spike at base-emitter junction by the employments of an n-type GaAs emitter and an n-InGaAs quantum well. Consequently, the excellent performances of the studied device provide a promise for linear amplifiers and circuit applications.