Boosting the performance of ZnO microrod metal-semiconductor-metal photodetectors via surface capping of thin amorphous Al₂O₃ shell layer

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/Al₂O₃ 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 Al₂O₃ shell layer, as evidenced by steady-state and transient photoluminescence investigations. The photodetectors demonstrated suppressed dark current and increased photocurrent after capping the Al₂O₃ layer. Specifically, the ZnO/Al₂O₃ 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 ∼10⁴ under relatively weak light illumination (∼10 μW 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.