DC and high frequency models for heterojunction bipolar transistors

This paper presents a detailed model which accurately predicts DC, small-signal and noise characteristics of AlGaAs-GaAs heterojunction bipolar transistors (HBTs). The features to the DC model are thermionic emission and tunneling effects at the base-emitter junction, calculation of various recombination currents, which contribute to the total base current. We introduce a new set of noise equations, which takes into account the correlation and frequency dependencies of the intrinsic noise sources. Compared to the SPICE noise model, this model provides further improvement in predicting small signal and large signal noise for HBT based circuits. These models can be easily implemented into any SPICE or harmonic balance simulators. The results of our study are validated using devices from different foundries.