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

Abstract

AbstractWe 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)