MBE growth of heavily carbon doped GaAsSb on InP for heterojunction bipolar transistor applications

Carbon doped GaAsSb samples have been grown by solid source molecular beam epitaxy using carbon tetrabromide as carbon source. A maximal hole concentration of 4.5×1020 cm−3 has been obtained with a corresponding mobility of 19 cm2/V s. For hole concentrations in the 4–8×1019 cm−3 range, typically used in HBTs, the hole mobility is 45–50 cm2/V s. We show that 450 °C is the optimal growth temperature at which both high hole concentration and mobility are obtained. An InP/GaAsSb/InP DHBT test structure with a 2×1019 cm−3 carbon doped base has been realised. The current gain β is about 80 and the emitter–base and base–collector junction ideality factors are 1.15 and 1.05, respectively, indicating good junction properties.