High performance normally-off self-aligned metal gate GaN MISFETs on free-standing GaN substrates

This paper describes characteristics of normally-off mode GaN MISFETs fabricated on free-standing GaN substrates with high drain current Idss and specific low leakage current between adjacent devices. Nitrogen ion implantation isolation processes were adopted to fabricate isolation regions in self-aligned GaN MISFETs for the first time. Maximum drain current of 98 mA/mm, maximum trans conductance of 10 mS/mm and threshold voltage of +0.4 V were obtained for the devices. The leakage current between adjacent devices was low, i.e., in the range of 10–6 mA/mm, which is three orders of magnitude lower than those on sapphire substrates. These supreme results indicate a definite availability of normally-off self-aligned GaN MISFETs for power switching device applications. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)