Effect of post-gate RTA on leakage current (Ioff) in GaN MOSHEMTs



Effect of post-gate rapid thermal annealing (RTA) on GaN metal-oxide semiconductor high electron mobility transistors (MOSHEMTs) performance has been investigated. For devices with 1-µm gate length and 10-µm gate width, a significant reduction of Iofffrom 10-4 to 10-6 mA/mm (at Vgs = -8 V, Vd= 6 V) was observed after post-gate RTA at 600 °C, indicating an excellent ON/OFF drain current ratio (Ion/Ioff) up to 108. The reduction of Ioffis mainly dominated by the decreased reverse-biased gate leakage current, as indicated by the strong dependence of Ion/Ioff on reverse-biased gate leakage current. The reduced gate leakage after post-gate RTA probably stems from the increased gate barrier height as a result of gate metal reaction with Al2O3. The degradation in pulse I-V characteristics may be due to defect formation in devices during post-gate RTA at 600 °C. Nearly complete recovery was achieved by further post-gate RTA at 400 °C for 10 minutes. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)