Investigation of trap states under Schottky contact in GaN/AlGaN/AlN/GaN high electron mobility transistors

Forward gate-bias stress experiments are performed to investigate the variation of trap states under Schottky contact in GaN-based high electron mobility transistors. Traps with activation energy E-T ranging from 0.22 eV to 0.31 eV are detected at the gate-semiconductor interface by dynamic conductance technique. Trap density decreases prominently after stressing, particularly for traps with E-T>0.24 eV. X-ray photoelectron spectroscopy measurements reveal a weaker Ga-O peak on the stressed semiconductor surface. It is postulated that oxygen is stripped by Ni to form NiO upon electrical stress, contributing to the decrease in O-N donor sates under the gate contact. (C) 2014 AIP Publishing LLC.