Abstract: An 18-element small-signal equivalent circuit for GaN HEMTs is discussed.Two additional feedback resistances are incorporated into the intrinsic device to account for the leakage current from gate to source and drain compared with the conventional circuit structure.Furthermore,considering the distributed effects in high frequency applications,a new 20-element model is proposed and a corresponding direct extraction method is developed.The new modeling approach for GaN HEMTs is verified by comparing the simulated small-signal S-parameter,over wide frequency and bias ranges,with the measured data of a GaN HEMT with a 1μm gate length and a 200μm gate width.The results show that the 20-element modeling system is more accurate and stable in the high frequency application than that of the 18-element lumped model.

Key words: GaN HEMT, modeling, parameter extraction, error analysis