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

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 (less than or equal to30 mV), lower saturation voltage (less than or equal to0.5 V), uniform current gain (similar to25), lower operated voltage, higher breakdown voltage and improved characteristics as compared to those obtained from a conventional double heterojunction bipolar transistor structure.