Optoelectronic properties and interface state analysis of self-powered p-NiO/n-ZnO:Al UV photodetectors

Abstract This study aims to investigate the optoelectronic properties of a p-NiO/n-ZnO: Al heterojunction photodetector. To this end, the structural characterization of the metal-oxide films by spray pyrolysis technique was performed using XRD, SEM, and FTIR methods on films grown under the same conditions on glass substrates. In this context, XRD analysis demonstrated that the heterostructure was successfully obtained, while SEM images proved that cracks in the heterostructure tended to decrease in a manner that would affect the distribution of interface states. In the FTIR spectra, characteristic metal-oxide bonds were detected in the fingerprint region, even though dominant Si–O–Si vibrations in the 900–1100 cm⁻¹ range arose from the glass substrate. The photodetector performances were evaluated based on the Al/p-Si/ZnO: Al/NiO/Au structure. The device, displaying a Type-II band structure, can work in self-powered mode below 0 V. In the optoelectronic measurements, the dark current was determined to be 5.7 × 10⁻ 8 A, the maximal responsivity was 2.5 × 10⁻ 1 A/W, and the ON/OFF ratio was approximately 3 × 10 2 . The findings demonstrate that the produced hetero-junction is a promising candidate for high-sensitivity and energy-efficient UV photodetectors.