Collector vertical scaling and performance tradeoffs in 300 GHz SiGe HBTs

This study investigates the impact of the collector vertical scaling on the tradeoff between f_T and f_max with SiGe HBTs of ∼300 GHz performance. We further proceed to discuss its impact on the avalanche breakdown behavior of the devices. It is observed that the selectively implanted collector (SIC) dose variation affects f_T and f_max in opposite directions, in 300 GHz SiGe HBTs, which can be exploited to selectively optimize the devices for either f_T or f_max depending on the requirement from a given application. This trend also indicates, along with the observed SIC dose dependence of the breakdown voltages, that the traditional speed-breakdown voltage (BV) tradeoff is valid for f_T-BV, but not necessarily for f_max-BV.