Giant Detectivity of ZnO-Based Self-Powered UV Photodetector by Inserting an Engineered Back Gold Layer Using RF Sputtering

The realization of high-responsivity, self-powered and low-cost ultraviolet (UV) photodetector (PD) based on eco-friendly and earth-abundant compounds, remains far from satisfactory for future optoelectronic applications. In this paper, we demonstrated a new high-performance UV-PD based on planar ZnO thin-film, efficiently operating without any power supply. The proposed device was elaborated by evaporating an engineered back metallic layer onto the glass substrate and then depositing ZnO thin layer through RF sputtering technique. The sensor structural and optical properties were systematically analyzed by the techniques of X-ray diffraction (XRD) and UV-Vis absorbance spectrometry. The resulted ZnO UV-PD showcased a clear and distinctive photovoltaic behavior. Interestingly, it also demonstrated a high responsivity of 0.38A/W and a giant detectivity exceeding 10
¹⁴
Jones at zero bias, which is much higher than other reported self-powered UV-PD despite the use of an All-ZnO structure. The device photodetecting mechanism in self-driven mode was discussed using the energy band diagram, where the key role of the engineered back metallic layer in modulating the electric field distribution within the ZnO active region to effectively achieve an asymmetric behavior is emphasized. Therefore, the presented work offers a novel pathway to design high-responsivity self-powered UV-PDs based on a simple All-ZnO structure.