부산대학교 도서관

Passivation films are used in III-nitride (III-N) based devices to suppress current collapse and improve frequency performance. Several passivation films and deposition methods have the added effects of increasing the dc ON- and OFF-state currents in devices. In this paper, the physical mechanisms behind this current increase have been studied in both nanoribbon and planar devices with atomic-layer deposited Al 2 O 3 passivation. Increased tensile stress in the AlGaN layer due to passivation leads to an increase in the charge density in nanoribbon devices. Simultaneously, the mobility in nanoribbons increases after Al 2 O 3 passivation. These effects lead to a large ( $\sim 118$ %) increase in the saturation drain current in nanoribbon devices. In contrast, fixed positive charge at the Al 2 O 3 -AlGaN interface leads to a small ( $\sim 6$ %) saturation drain current increase in planar devices. In addition, the mechanisms behind the increase in the OFF-state drain current in the passivated devices are investigated. Schottky barrier lowering and the increase in surface and buffer conduction are found to be the major causes for the OFF-state current increase with passivation.