The influence of a δ-doped sheet on DC performances of InP/InGaAs heterojunction bipolar transistors

In this paper, we report the influence of a δ-doped sheet on the DC characteristics of InP/InGaAs δ-doped heterojunction bipolar transistors. The employment of a δ-doped sheet at the base-emitter (B-E) junction efficiently eliminates the potential spike at the B-E junction, lowers the collector-emitter offset voltage, and increases the confinement effect for holes, simultaneously. An analytical model related to the elimination of the potential spike and the components of base recombination currents is developed to investigate the transistor performances. Experimentally, for the studied device with a δ-doping density of 2×1012 cm−2, a maximum current gain of 455 and a low offset voltage of 55 mV are achieved. The experimental results are consistent with the theoretical analysis.