Evaluation of Pulsed I-V Analysis as Validation Tool of Nonlinear RF Models of GaN-Based HFETs

This paper evaluates the applicability of pulsed I-V measurements as a tool for accurately extracting nonlinear gallium nitride (GaN)-based heterojunction field-effect transistor (HFET) models. Two wafers with the identical layer structure but different growth conditions have been investigated. A series of I-V measurements was performed under dc and pulsed conditions demonstrating a dramatic difference in the kink effect and current collapse (knee walkout) suggesting different trapping behaviors. However, when radio frequency (RF) I-V waveform measurements, utilizing active harmonic load-pull, were used to study the impact of these traps on the RF performance, both wafers gave good overall RF performance with no significant difference observed. This absence of correlation between pulsed I-V measurement results and RF performance raises a question about the applicability of pulsed I-V measurements alone as a tool for extracting nonlinear device models in the case of GaN HFETs.