113-GHz fT graded-base SiGe HBTs

A novel low-thermal cyclc proccss was used to fabricatc epitaxial SiGe-base heterojunction bipolar transistors (HBTs) with record unity current gain cutoff frequencies. The process includes an in situ phosphorus-dopcd polysilicon emitter which requires only a 800°C-10s anneal. A peak f
_T
of 113 GHz at V
_CB
of 1V was obtained for an intrinsic base sheet resistance of 7 kΩ/square.