Field-induced defect morphology in Ni-gate AlGaN/GaN high electron mobility transistors

AlGaN/GaN high electron mobility transistors were electrically stressed using off-state high reverse gate biases. In devices demonstrating the largest, most rapid decrease in normalized maximum drain current, defects were found at the gate/AlGaN epilayer interface and characterized using high-angle annular dark-field scanning transmission electron microscopy. These defects appear to be a reaction between the Ni layer of the Ni/Au gate metal stack and the AlGaN epilayer. Additionally, simulations of the electric field lines from the defective devices match the defect morphology. These results provide important insight toward understanding failure mechanisms and improving reliability of Ni-gate AlGaN/GaN high electron mobility transistors. (C) 2013 AIP Publishing LLC.