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 IC 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 VBE and VCB modulation on IC is opposite for the two modes, leading to a smaller Early voltage but more ideal collector current for the reverse mode. © 2005 IEEE.