Individual Ohmic contacted ZnO/Zn2SnO4 radial heterostructured nanowires as photodetectors with a broad-spectral-response: injection of electrons into/from interface states

Abstract

ZnO and Zn₂SnO₄ nanowires (NWs) have relatively high sensitivities as ultraviolet (UV) photodetectors, while their bandgaps are an important limitation in their applications in the visible (VIS) and near-infrared (NIR) ranges. In this paper, we demonstrate the promising applications of Ohmic contacted individual Zn₂SnO₄-sheathed ZnO core/shell radial heterostructured NWs as high performance solar blind UV-VIS-NIR photodetectors with a relatively high sensitivity, stability, and reproducibility. The dominant mechanism for the excellent photoconductivity is attributed to the presence of interface states in the II-type heterostructure, which prevents the movement of charge at the heterointerface. Upon applying a negative bias voltage at one end of the detector, where the interface states will be filled, potential barriers will decrease and be eliminated. Therefore, photogenerated electron–hole pairs will be separated efficiently and electrons can migrate towards the Zn₂SnO₄ shell, resulting in a huge decrease in shell resistance. The absorption of the heterointerface and charged oxygen vacancies (V⁺_O and V⁺⁺_O) in the depletion region can induce VIS and NIR photoresponses. These results demonstrate that individual heterostructured NWs composed of wide bandgap semiconductors can indeed serve as high-performance photodetectors in the solar blind UV-VIS-NIR range.