Novel Cu–Mg–Ni–Zn–Mn oxide thin film electrodes for NIR photodetector applications

This study reports the optical and photoconductive characteristics of the Cu–Mg–Ni–Zn–Mn oxide thin films with and without post-annealing in air. The Cu–Mg–Ni–Zn–Mn oxide thin films reveal a narrow bandgap of 1.96 eV and demonstrate the characteristics of an n-type semiconductor. The thin films exhibit a spinel crystal structure characterized by X-ray diffractometer and transmission electron microscopy. The p+-Si-substrate/Cu–Mg–Ni–Zn–Mn-oxide/indium-tin-oxide sandwich-structure devices were fabricated for the photoconductive characteristic investigation of Cu–Mg–Ni–Zn–Mn oxide thin films deposited by radio-frequency (RF) sputtering. The devices showed a high external quantum efficiency (EQE) of 96% under 800 nm wavelength illumination at a bias of −2 V. A fast response rise-time of 13 ms and a fall-time of 11 ms were also obtained. Hence, the Cu–Mg–Ni–Zn–Mn oxide thin films pave the way for developing high efficiency Schottky barrier photodetectors.