Effect of Growth Time on the Photoresponse of n-ZnO NWs/p-Si Self-powered Ultraviolet Photodetectors Prepared by Hydrothermal Method

ZnO nanowires (ZnO NWs) were grown on p-Si (100) substrates by hydrothermal method to construct n-ZnO NWs/p-Si self-powered ultraviolet photodetectors (UVPDs). As the growth time increases, the axial/lateral growth rate ratio of ZnO NWs increases, whereas their density and orientation consistency decrease for the competitive growth between vertical and tilted nanowires. All ZnO NWs show an obvious UV emission, which position shifts toward lower energy side attributed to the increased diameter and bending of ZnO NWs with increasing growth time. The current-voltage curves of all UVPDs present a typical rectifying behavior in the dark. Under UV illumination, their photocurrents are obviously enhanced, and the maximum photocurrent at zero bias is obtained for the device with ZnO NWs growth time of 6 h, indicating good self-powered performance. Meanwhile, it displays a relatively fast response performance, which is attributed to the large specific surface area and higher aspect ratio of ZnO NWs.