Optimization of emitter cap growth conditions for InGaP/GaAs HBTs with high current gain by LP-MOCVD

The effect of emitter cap growth conditions on the common-emitter current g ain of InGaP/GaAs HBTs, grown by LP-MOCVD, has been studied. This work show s that the material quality of a carbon-doped base is highly dependent on t he emitter cap growth. The emitter cap growth effectively serves as a sourc e of thermal stress. This stress on the base during the emitter and cap gro wth causes the formation of carbon-related defects in the base that increas e the base recombination and reduces the current gain. Atomic force microsc opy is used to identify these carbon-related defects. Gain improvements of about 40% have been achieved by optimizing the emitter cap growth condition s to reduce the thermal stress.