We develop a theoretical model related to minority carrier properties to study the current gains of heterostructure-emitter bipolar transistors (HEBTs) which use an AlGaAs layer only for minority carrier confinement to eliminate the problems associated with a conventional single heterojunction bipolar transistor (HBT). In this study, minority carrier properties were described by means of polynominal fit to the previous data. Here, the band-gap shrinkage in heavily doped layers" was also taken into account. Current gains of 55 and 180 which are in agreement with calculated data were experimentally obtained for HEBTs with Al0.3Ga0.7As and Al0.5Ga0.5As confinement layers, respectively. With the reduction of the base width to 0.1 μm, a current gain of around 1000 was expected.