Analysis of buffer‐related lag phenomena and current collapse in GaN FETs

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 LG (0.3 μm – 1 μm), and this is essentially determined by a deep‐acceptor density NDA in the buffer layer. LG and NDA dependence of gate lag is also studied, indicating that the gate lag is weaker for longer LG and the lag rate becomes high with NDA, although it may show a saturation behaviour. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)