Modelling of gain control in SiGe HBTs and Si bipolar transistors by Ge incorporation in the polysilicon emitter

摘要

This paper reports a theory for the base current in which Ge is incorporated in the polysilicon emitter. The competing influences of the Ge and the interfacial layer at the polySiGe/Si interface are investigated theoretically using an effective surface recombination velocity for the polySiGe emitter. A comparison with measured results is made and good agreement obtained. A Ge content of 19% gives a base current reduction by a factor of approximately four.