Analysis of buffer-trapping effects on current collapse of GaN FETs

Two-dimensional transient simulation of GaN MESFETs is performed in which a deep donor and a deep acceptor in a semi-insulating buffer layer are considered. Quasi-pulsed I-V curves are derived from the transient characteristics, and are compared with the steady-state I-V curves. It is shown that the current collapse is more pronounced when the deep-acceptor density in the buffer layer is higher and when an off-state drain voltage is higher, because the trapping effects become more significant. It is suggested that to minimize current collapse in GaN-based FETs, an acceptor density in a semi-insulating GaN layer should be made low, although the current cutoff behaviour may be degraded.