RF large-signal model for SiO2/AlGaN/GaN MOSHFETs

For the first time, an RF large-signal model for GaN-based metal-oxide-semiconductor heterojunction field-effect transistors is extracted and validated. The model is based on the commercially available EEHEMT model that was originally developed for GaAs MODFETs. The model parameters were extracted from current-voltage characteristics and S parameters measured under both CW and pulsed conditions. The terminal impedances were extracted through global fitting over a wide frequency range, while the gate leakage across the oxide was modeled by a Schottky contact with a large ideality factor. Although the model simulates the Class-A power-amplifier performance of the unit transistor rather well, the EEHEMT model was found lacking provisions for gate capacitance nonlinearity and self-heating effects that are required for large transistors in reduced-angle power amplifiers.