Extension of common-emitter breakdown voltage for high speed Si/Si 1-xGex HBT´s

Various collector structures were simulated to identify design options which lead to an increase in the breakdown voltage of high speed SiGe-base heterojunction bipolar transistors (HBTs). The authors propose an approach for increasing the breakdown voltage by appropriately tailoring the doping profile in the collector. A two-part collector doping profile was found to reduce the avalanche multiplication ratio by more than an order of magnitude. Simulation results indicate that this improvement can be achieved without severe degradation of the base pushout effect