Analysis of buffer-trapping effects on current reduction and pulsed I-V curves of GaN FETs

Two-dimensional transient analyses of GaN MESFETs are performed in which a three level compensation model is adopted for a semi-insulating buffer layer, where a shallow donor, a deep donor and a deep acceptor are included. Quasi-pulsed I-V curves are derived from the transient characteristics. It is shown that so called current collapse or current reduction is more pronounced for a case with higher acceptor density in the buffer layer, because trapping effects become more significant. It is also shown that the current reduction is more pronounced when the drain voltage is lowered from a higher drain bias during turn-on.