Theoretical investigation of an InGaP/GaAs heterostructure-emitter bipolar transistor with a wide-gap collector

Abstract

We theoretically analyse the performance of an InGaP/GaAs heterostructure-emitter bipolar transistor (HEBT) with a wide-gap collector. Using an exact simulation, we report on detailed calculations and studies including majority-carrier and minority-carrier profiles, recombination-rate distributions, and dc and ac performances. By introducing an undoped GaAs spacer and a heavily doped transition layer into the conventional base–collector heterojunctions, the field across the inserted layers is high enough to pull down the potential spike drastically; thus the knee-shaped characteristics and reach-through effect are not observed. Moreover, the base–emitter (B–E) structure, which we have used, contains an effective p–n homojunction and a hetero-confinement layer to substantially reduce the potential spike at the B–E junctions. Therefore the studied device has exhibited a relatively smaller offset voltage and higher current gain than those of a conventional heterojunction bipolar transistor. The simulated results particularly reveal that a proposed HEBT with an appropriately designed device structure exhibits higher efficiency, lower offset voltage (≤30 mV), lower saturation voltage (≤0.5 V), uniform current gain (∼25), lower operated voltage, higher breakdown voltage and improved characteristics as compared to those obtained from a conventional double heterojunction bipolar transistor structure.