Investigation of SiGe HBT potentialities under cryogenic temperature

This paper focuses on small signal and noise performances of Si/SiGe:C heterojunction bipolar transistors (HBT) under cryogenic temperatures. Two different technologies featuring state-of-the-art cutoff frequencies respectively for f
_T
and f
_MAX
are investigated. State-of-the-art minimum noise figures are reported both at room and cryogenic temperatures. A T small signal equivalent model to which is added a noise model has been extracted and is used to discuss the improvement of HBT performances at cryogenic temperatures.