Reverse active mode current characteristics of SiGe HBTs

The current characteristics of SiGe heterojunction bipolar transistors (HBTs) operating in the reverse active mode are investigated. It is experimentally shown that the I/sub C/ is identical for the reverse and the forward modes for arbitrary doping and Ge profiles across the base to first order. In contrast, the impact of V/sub BE/ and V/sub CB/ modulation on I/sub C/ is opposite for the two modes, leading to a smaller Early voltage but more ideal collector current for the reverse mode.