An analytical model of the inverse base width modulation effect in SiGe graded heterojunction bipolar transistors

Abstract

The analytical model of the collector current ideality factor degradation at high V be in modern SiGe graded base heterojunction bipolar transistors (HBTs) has been developed for the first time. It is subsequently used for the analysis of the inverse base width modulation (IBWM) effects in SiGe HBTs with respect to collector current degradation, current gain premature roll-off and SiGe base transit time. Comparing the IBWM effects calculated for HBTs with various base impurity concentration doping profiles and the Ge grading, we have found that the careful optimization of SiGe base parameters may substantially minimize negative influence of the IBMW effects on the HBT electrical parameters.