Improvement of the electrical properties of Al2O3/AlGaN/GaN MOSHFETs by gate-first process

Abstract

We have studied "gate-first process" in the fabrication of the Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) to improve the electrical properties of the MOSHFETs, where Al2O3 gate oxide is deposited before ohmic contact alloying. The interface state density of the Al2O3/GaN MOS diodes fabricated by the gate-first process was more than one order of magnitude smaller than that of the diodes fabricated by the conventional "gate-last process" where Al2O3 gate oxide was deposited after ohmic contact alloying. In addition, the saturation of the drain current at large gate voltages in the ID-VGS characteristics of the Al2O3/AlGaN/GaN MOSHFETs was relaxed and the maximum drain current was increased by employing the gate-first process. The hysteresis width of the ID-VGS curve of the MOSHFETs fabricated by the gate-first process was smaller than that of the devices fabricated by the gate-last process. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.