Lumped Models for Assessment and Optimization of Bipolar Device RF Noise Performance

Abstract

We present a method for simulation of RF noise characteristics of both intrinsic and complete Si(Ge) heterojunction bipolar transistors (HBT's), aiming at support for device design and optimization. RF noise at the intrinsic device level is addressed through an equivalent circuit based on a discretization of partial differential equations describing the transport of minority carriers in quasi-neutral regions. Effects of nonuniform impurity/bandgap distribution and finite velocity recombination at the polysilicon emitter contact are accounted for. Accuracy is verified against analytical results at intrinsic device level. Assessment of noise characteristics of a complete industrial SiGe HBT demonstrates the practical relevance of nonquasi-static effects on noise characteristics. Exploration of the impact of intrinsic base doping profiles on noise performance demonstrates the potential for device optimization.