Hot carrier-induced degradation and gamma radiation-induced degradation in silicon-germanium HBTs and VCOs

Reverse-bias electrical stressing causes degradation of the base current and current gain of SiGe HBTs. Two types of hot carrier stressing were used in this study: open-collector (OC) stressing and forward-collector (FC) stressing. Gamma irradiation results in changes to the HBT collector current similar to the changes seen during electrical stressing. Reverse-bias electrical stressing causes damage in the base-emitter (BE) junction while irradiation causes damage in both the BE junction and the base-collector (BC) junction. Gamma irradiation of transistors also causes degradation in the phase noise of voltage controlled oscillators (VCOs) made from SiGe HBTs.