Abstract
Self-assembled AlGaN nanowires (NWs) are regarded as promising structures in the pursuit of ultraviolet photodetectors (UV PDs). However, AlGaN NW-based PDs currently suffer from degraded performance partially due to the existence of outstanding surface-related defects/traps as a result of their large surface-to-volume-ratio. Here, we propose an effective passivation approach to suppress such surface states via tetramethyl ammonium hydroxide (TMAH) solution treatment. We successfully demonstrate the fabrication of UV PDs using TMAH-passivated AlGaN quantum-disk NWs and investigate their optical and electrical properties. In particular, the dark current can be significantly reduced by an order of magnitude after surface passivation, thus leading to the improvement of photoresponsivity and detectivity. The underlying mechanism for such a boost can be ascribed to the effective elimination of oxygen-related surface states on the NW surface. Consequently, an AlGaN NW UV PD with a low dark current of 6.22 x 10(-9) A, a large responsivity of 0.95 A W-1, and a high detectivity of 6.4 x 10(11) Jones has been achieved.