Al2O3 surface passivation and MOS-gate fabrication on AlGaN/GaN high-electron-mobility transistors without Al2O3 etching process

Al2O3 passivation by thermal oxidation of aluminium on AlGaN/GaN high-electron-mobility transistors (HEMTs) without Al2O3 etching is proposed. The deposition of a 5-nm-thick Al film was carried out, followed by a lift-off process to remove Al from the ohmic and contact pad area. Subsequently, the Al film was annealed under O-2 ambient. When the gate bias was -7V, the gate leakage currents of a conventional nonpassivated HEMT, a surface-passivated Schottky-gate HEMT, and a surface-passivated MOS-HEMT were determined as 140, 96, and 4.1 mu A/mm, respectively. The current collapse phenomenon in the Al2O3-surface-passivated devices was evidently suppressed compared with that in the nonpassivated HEMT. (C) 2015 The Japan Society of Applied Physics