Fast speed UV photodetector with high responsivity based on ZnO/MgZnO core–shell nanowires

Ultraviolet (UV) photodetectors based on zinc oxide (ZnO) wide-bandgap semiconductors have been intensively explored for applications in environmental monitoring, optical communication, and biosensing. However, conventional ZnO-based photodetectors often suffer from limited responsivity and relatively slow photoresponse speeds, which severely restrict their practical applications. Herein, we report a highly sensitive and fast-responsive photodetector based on ZnO/MgZnO core–shell radial-heterostructured nanowires (NWs) through radial interface engineering. The introduction of a wider bandgap MgZnO shell onto ZnO NWs forms a radial ZnO/MgZnO heterojunction, which introduces a built-in electric field that effectively promotes the separation and collection of photogenerated carriers. The optimized device exhibits a fast response time of 0.41/2.30 s (rise/decay) and a high responsivity of 0.75 A/W at zero bias. Furthermore, this study reveals a nonlinear relationship between the MgZnO shell thickness and the photoresponsivity of the device, and identifies the optimal MgZnO shell thickness for optimizing device performance. These results demonstrate that core–shell heterointerface engineering is an effective strategy for balancing responsivity and response speed in ZnO-based UV photodetectors.