Impact of Ge Profile on TID Susceptibility of SiGe HBTs

The impact of Ge profile on the TID susceptibility of SiGe HBTs from two manufacturers is investigated based on TCAD simulation. The results indicate that the modulation of potential distribution across the base region by Ge grading has significant impacts on the base current degradation. The Box Ge profile can cause a strong retarding potential near the EB junction, thereby leading to high recombination rates at the trap-enriched EB-spacer/SiGe interface. While Ge profiles with high accelerating field near the EB junction can prevent the injected carriers from diffusing to the EB-spacer/SiGe interface and suppress the increase of excess base current. Besides, this impact of Ge profile is closely related to the base thickness and integrated Ge content.