Comparative Investigation of InGaP/GaAs/GaAsBi and InGaP/GaAs Heterojunction Bipolar Transistors

In this article the characteristics of In$_{0.49}$Ga$_{0.51}$P/GaAs/GaAs$_{0.975}$Bi$_{0.025}$ and In$_{0.49}$Ga$_{0.51}$P/GaAs heterojunction bipolar transistor (HBTs) are demonstrated and compared by two-dimensional simulated analysis. As compared to the traditional InGaP/GaAs HBT, the studied InGaP/GaAs/GaAsBi HBT exhibits a higher collector current, a lower base-emitter $(B-E)$ turn-on voltage, and a relatively lower collector-emitter offset voltage of only 7 mV. Because the more electrons stored in the base is further increased in the InGaP/GaAs/GaAsBi HBT, it introduces the collector current to increase and the $B$–$E$ turn-on voltage to decrease for low input power applications. However, the current gain is slightly smaller than the traditional InGaP/GaAs HBT attributed to the increase of base current for the minority carriers stored in the GaAsBi base.