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 fT and fmax 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 fT and fmax in opposite directions, in 300 GHz SiGe HBTs, which can be exploited to selectively optimize the devices for either fT or fmax 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 fT-BV, but not necessarily for fmax-BV.