Modelling base transport properties of npn SiGe HBT

Abstract

The modelling of the collector current and the base transit time in npn SiGe HBT is presented. The evaluation of minority electron concentration in the base and its dependence on doping concentration, temperature and Ge content is discussed in detail. It is shown that Ge-induced performance improvement of SiGe HBTs compared to Si BJTs is lowered at high doping concentrations in the base due to invalidity of Boltzmann statistics, which is more influential in SiGe due to lower hole effective mass.