Effect of high-temperature annealing for single-Ni-layer gate in AlGaN/GaN high-electron-mobility transistors

AlGaN/GaN high-electron-mobility transistors (HEMTs) with Schottky gate contacts are strong candidates for high-power applications with high-frequency operation. The existence of interfacial traps between Schottky gate contacts and an AlGaN surface is one of the issues causing relatively high gate leakage current in these HEMTs. High-temperature gate annealing, which reduces the density of traps owing to the interfacial reaction between Schottky gate contacts and an AlGaN surface, was investigated using a single-Ni-layer gate structure to prevent the alloying of conventional stacked metal layers such as Ni/Au and Pt/Au. As a result, a strong gate annealing temperature dependence of Schottky characteristics was observed and this dependence also caused drain current collapse. In addition, it was confirmed that 700 degrees C is the optimal gate annealing temperature for improving both the Schottky characteristics and drain current collapse. These results are attributed to the change in the density of interfacial trap states. (C) 2016 The Japan Society of Applied Physics