Evaluation of the hot carrier/ionizing radiation induced effects on the RF characteristics of low-complexity SiGe heterojunction bipolar transistors by numerical simulation

The hot carriers (HC)/ionizing radiation (IR) effects on the DC and RF characteristics of Si/SiGe HBTs have been investigated by numerical simulations. Once reproduced the typical DC degradation modes, the changes in the scattering (S) parameters were investigated up to 30 GHz. The degradation is caused by the increase of the Shockley-Hall-Read (SHR) surface recombination located around the emitter perimeter. Simulations were carried out by keeping the base or the collector current as they were before introducing the degradation mechanism. When the base current is kept constant, the most relevant effect is a reduction of \ S-21\ while the other S-parameters exhibit only minor changes. On the other hand, no remarkable hot carrier/ionizing radiation effects on the RF characteristics were observed when the collector current was kept constant. (C) 2000 Elsevier Science Ltd. All rights reserved.