Performance optimization of Pnp InGaAs/InP heterojunction phototransistors

Fabrication, physical simulation, and optimization of two-terminal Pnp heterojunction phototransistors (2T-HPTs) based on In0.53Ga0.47As/InP are reported. The parameters of fundamental models are determined by comparing the simulated current and response characteristics with the experimental results. To optimize the optical gain and device performance, the precise adjustment of the base doping level, base width, and compositional grading of base has been investigated. Properly reducing the base width or increasing the range of the compositional grading can greatly enhance the emitter injection efficiency. The effects of high-low doping in collector region and the insertion of a thin, undoped InGaAs layer in the base region of the HPT have also been investigated in detail. It is found the high-low doping in collector can form an electric field to aid carrier transport, and the intrinsic layer between emitter and base has functions of reducing knee voltage and the dark current of HPT.