Physical property based HBT models for SPICE simulation

A one-dimensional analytical model for both graded-base and uniform-base AlGaAs/GaAs Heterojunction Bipolar Transistors (HBTs) with or without band spikes is presented. The model is based on Physical Property Based Equations (PPBEs). The PPBEs are arranged in a form which allows a commercial CAD package (Cadence) to predict the SPICE parameters directly from a transistor profile which specifies the doping, thickness, material properties, energy band structure, and dimensions of the transistor. Implementing the PPBEs within a CAD package provides a powerful tool for a circuit designer. The designer is given the flexibility to investigate the effect of modifications in the transistor profile on the circuit performance, without being restricted to a particular technology. Hence, the design based on this work will be a truly custom integrated circuit design not constrained by the limitations of any technology libraries. The accuracy of the model is tested by comparing predicted SPICE parameters with parameters obtained from fitting to measured transistor characteristics. The predicted I-V characteristics are also compared with the measured characteristics.