High emitter efficiency in InP/GaInAs HBT's with ultra high base doping levels

The emitter efficiency of InP/GaInAs heterojunction bipolar transistors is calculated taking into account bandgap narrowing in the base, quantum mechanical tunneling, and the exact doping profile in the base. It is found that the emitter efficiency is high and does not limit the current gain of practical devices, up to a base doping level of 1/spl times/10/sup 20/ cm/sup -3/, and up to 400/spl deg/K . It is shown that the base emitter junction saturation current can be controlled over two orders of magnitude by a proper small displacement of the doped layer in the base.<
>