A Procedure for GaN HEMT Charge Functions Extraction from Multi-Bias S-Parameters

A charge function identification procedure for GaN-HEMTs is proposed. This is based on a frequency-domain integration of displacement current waveforms obtained from an auxiliary model extracted from multi-bias S-parameters. The method is compared with a similar technique recently proposed, which is instead based on direct acquisitions of large-signal waveforms at the transistor ports by means of a nonlinear vector network analyzer (NVNA). Comparisons between the two approaches are provided by using a 1-mm GaN-on-SiC HEMT, leading to conclude that thermal and trap-induced dispersion on charges have an impact quantified in ∼ 4% − 18% normalized mean square error on the displacement current prediction, depending on the waveforms considered.