Analysis of buffer-related lag phenomena and current collapse in GaNFETs

Drain-current responses of GaN MESFETs with a semi-insulating buffer layer are calculated when the drain voltage and/or the gate voltage are changed abruptly, and pulsed I-V curves are derived from them. It is shown that so-called current collapse or current slump is not so dependent on the gate length L-G (0.3 gm - 1 mu m), and this is essentially determined by a deep-acceptor density N-DA in the buffer layer. L-G and N-DA dependence of gate lag is also studied, indicating that the gate lag is weaker for longer L-G and the lag rate becomes high with N-DA, although it may show a saturation behaviour. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.