Effective surface passivation of GaAs nanowire photodetectors by a thin ZnO capping

The III-V nanowire (NW) structure is a good candidate for developing photodetectors. However, high-density surface states caused by the large surface-to-volume ratio severely limit their performance, which is difficult to solve in conventional ways. Here, a robust surface passivation method, using a thin layer of ZnO capping, is developed for promoting NW photodetector performance. 11 cycles of ZnO, grown on pure zinc blende high-quality GaAs NWs by atomic layer deposition, significantly alleviates the undesirable effect of the surface states, without noticeable degradation in NW morphology. An average 20-fold increase in micro-photoluminescence intensity is observed for passivated NWs, which leads to the development of detectors with high responsivity, specific detectivity, and optical gain of 9.46 × 10⁵ A W^-1, 3.93 × 10¹⁴ Jones, and 2.2 × 10⁸ %, respectively, under low-intensity 532 nm illumination. Passivated NW detectors outperform their counterparts treated by conventional methods, so far as we know, which shows the potential and effectiveness of thin ZnO surface passivation on NW devices.