Device Simulation for Advanced Si xub 1-x Ge sub x HBTs

Accurate simulations of advanced Si sub 1-x Ge sub x heterojunction bipolar transistors involve a range of different problems, whose solution demands different numerical approaches. In our simulation methodology, the complexity of each numerical method matches that of the problem at hand. We employ a 2D drift-diffusion solver for dc and ac characteristics, ID full-band Monte Carlo for transport in the base-collector high electric field region, and a 3D heat-transfer solver for device self-heating. Extrinsic parasitics are introduced as lumped circuit elements whose values are obtained from measurements. This approach not only reduces the computational cost of the simulation, but it also helps to differentiate the relevance of the intrinsic and extrinsic device parameters. Such information can then be used for device optimization and for guidance in generating compact models.