Photoactive Copper-Doped Zinc Stannate Thin Films for Ultraviolet–Visible Light Photodetector

A photodetector capable of detecting light illuminations ranging from ultraviolet (UV) to visible light spectrum using earth-abundant and environmentally friendly Cu-doped zinc tin oxide (Cu-doped ZTO) thin films is reported. Trilayer photodetector devices comprising P+-Si/10 at.% Cu-doped-ZTO-thin-film/indium-tin-oxide were successfully fabricated using radio-frequency (RF) magnetron sputtering. Optical and photoconductive characteristics of trilayer photodetector devices were investigated. The devices were found to exhibit superior photodetection capabilities, including high sensitivities of 1147 and 758, under 630-nm and 352-nm light illumination, respectively, and corresponding fast photoresponse times with a rise-time/fall-time of 8.9 ms/8.0 ms and 8.8 ms/8.0 ms. The induced mid-gap states from the Cu-dopant contributed extensively to the photoresponse through stable optical transitions. Air-annealing the Cu-ZTO thin films at 600°C effectively reduced the dark current, enabling Cu-ZTO thin films suitable for UV–visible light, wide spectral photodetector applications.