Boosting the performance of ZnO microrod metal-semiconductor-metal photodetectors via surface capping of thin amorphous Al 2 O 3 shell layer

Abstract 1D ZnO nanostructures have been widely explored due to their potential applications in ultraviolet (UV) region photodetectors because of their unique structural and optoelectronic properties. However, a large number of surface defect states leading to a noticeable dark current hinders their practical applications in UV photodetection. In this work, we have shown improved ZnO/Al 2 O 3 core–shell microrod photodetectors, whose performance is significantly enhanced by defect passivation and the introduction of trap states by atomic layer deposition grown thin amorphous Al 2 O 3 shell layer, as evidenced by steady-state and transient photoluminescence investigations. The photodetectors demonstrated suppressed dark current and increased photocurrent after capping the Al 2 O 3 layer. Specifically, the ZnO/Al 2 O 3 core–shell microrod photodetector exhibited a photoresponsivity as high as 0.019 A/(W cm −2 ) with the dark current as low as ∼1 × 10 −11 A, and a high I light / I dark ratio of ∼10 4 under relatively weak light illumination (∼10 μ W cm −2 ). The results presented in this work provide valuable pathways to boost the performance of 1D ZnO microrod-based photodetectors for future practical applications.