Modeling Nonquasi-Static Effects in SiGe HBTs

The shortcomings of quasi-static and partitioned charge-based models are quantitatively demonstrated for 1-D SiGe heterojunction bipolar transistors. This points out the need to include higher order frequency-dependent terms, i.e., nonquasi-static effects in the model. Three different implementation-suitable modeling approaches are presented with associated formulations. Detailed comparison with the original theory is carried out to show the different levels of achievable accuracy of the formulated models. Circuit simulator implementations, parameter extractions, and validations of the models with device simulation results are also carried out. Frequency- and time-domain small-signal modeling results are found to be consistent and provide a high level of accuracy. For two selected cases among the various modeling approaches, results of large-signal transient switching are presented, showing excellent agreement with device simulation.