Edge‐field effects on gate capacitance, threshold voltage and low‐field mobility in AlGaN/GaN HEMTs

Abstract

AbstractA methodologybased on output conductance model and pulsed current–voltage characteristics is presented for device parameter extraction in AlGaN/GaN HEMTs. A quiescent bias of (VDSQ, VGS Q) = (0 V, 0 V) and 0.2 µs pule width with 2 ms separation are applied to ensure that all the pulsed measurementsare performed under trap‐free operation condition.The results show that HEMTs with a shorter gate length exhibit a more negative threshold voltage, a lower low‐field mobility, and a higher capacitance than the theoretical AlGaN barrier capacitance. This is because edge field effect becomes significant in a shorter gate together with a higher lateral field effect. By comparing the measured and theoretical capacitances of AlGaN barrier, effective gate lengths are also estimated for HEMTs with different gate lengths. It is suggested that our method including the edge‐field effect is an effective way for evaluating newly‐introduced growth/processing technologies and monitoring device processing (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)