Impact of gamma irradiation on the RF phase noise capability of UHV/CVD SiGe HBTs

This work investigates the effects of gamma irradiation on the residual phase noise of SiGe HBTs. The excellent phase noise capabioity of SiGe HBT is retained after 1Mrad(si) irradiation. The observed radiation hardness is attributed to the minor changes in the low frequency noise and device nonlinearities after irradiations, as well as the nonlinearity cancellation mechanism. The radiation-induced defects do not significantly add to the low frequency noise in these SiGe HBTs, even though they produce a large space-charge-region recombination component in the base current. The inherent excellent linearity of these SiGe HBTs makes the up-conversion from device low frequency noise to phase noise inefficient, and helps to retain the low pahse noise after irradiations.