Sensitivity Enhancement of Ultraviolet Photodetectors With the Structure of p-NiO/Insulator-SiO 2 /n-ZnO Nanowires

A high-performance photodetector with the structure of NiO/SiO 2 /ZnO nanowires has been proposed. The devices with 6-nm-thick SiO 2 exhibited a better rectification ratio ( $J_{\mathrm {forward}} / J_{\mathrm {reverse}})$ of 246 at ±2 V, lower dark current density ( $J_{\mathrm {dark}})$ of $3.5\times 10^{\mathrm {-7}}$ A/cm $^{2}$ at a reverse bias of 2 V, and superior ultraviolet (UV) sensitivity ( $I_{\mathrm {UV}} / I_{\mathrm {dark}})$ of 16.23 than those without the SiO 2 layer ( $J_{\mathrm {forward}} / J_{\mathrm {reverse}} = 44, J_{\mathrm {dark}} = 4.7\times 10^{\mathrm {-6}}$ A/cm $^{2}$ , and $I_{\mathrm {UV}} / I_{\mathrm {dark}} = 5.5)$ . The improved performance was mainly due to the ultrathin inserted SiO 2 layer that builds a barrier height to minimize the transmission probability of low-energy carriers, leading to the enhancement of the UV sensing characteristics.