Tak H. Ning
ESSDERC 1987
An analytical model is developed for evaluating the effect of emitter depth variation on base and collector currents in a polysilicon-emitter SiGe-base bipolar transistor. It is shown that the base current is relatively insensitive to the Ge distribution in the single-crystalline emitter region, consistent with reported experimental results. On the other hand, the collector current and Early voltage are functions of the Ge distribution, Ge-free cap thickness, and final emitter depth. In particular, the current gain and Early voltage could have a strong dependence on emitter depth when there is a residual Ge-free layer left in the final quasi-neutral base. However, if the emitter-base junction is located in a constant-Ge region, then large current gains can be achieved that are relatively insensitive to emitter-depth variation, consistent with reported results. The inverse relationship between current gain and Early voltage is noted and contrasted with that of a wide-gap-emitter HBT.
Tak H. Ning
ESSDERC 1987
Ghavam G. Shahidi, Carl A. Anderson, et al.
IEEE Transactions on Electron Devices
Sufi Zafar, Marwan Khater, et al.
Applied Physics Letters
Tak H. Ning
VLSI-TSA 2013