| A physics-based approach to the compact modeling of GaAs-based and InP-based HBTs is described. Detailed analysis of device operation and topology is utilized in order to include physical effects that are specific to the AlGaAs/GaAs HBTs, InGaP/GaAs HBTs, InP/InGaAs HBTs and at the same time to avoid modeling effects that are not relevant. Among the effects incorporated into the model are self-heating, base push-out (Kirk effect), non-trivial bias dependence of transit times and depletion capacitances, base-collector diffusion charge in saturation and quasi-saturation, non-quasi-static effects in both base and collector regions. It is shown that the non-quasi-static effects can be naturally added to the quasi-static model without further complicating equivalent circuit topology. The result is a concise but capable large-signal compact model together with a clear and practical extraction procedure for model parameters. The model is designed to be compatible with the majority of the today's industry-standard compact BJT models (VBIC, MEXTRAM, HICUM, UCSD). This allows simple mapping of the proposed model into any of the industry-standard ones hence alleviating problems associated with implementation of a user-defined model. An example of conversion into the VBIC model is also presented. |
