Self-powered GaN ultraviolet photodetectors with p-NiO electrode grown by thermal oxidation

Self-powered ultraviolet photodetectors based on n-GaN and p-NiO were fabricated through thermal oxidation. The transparent NiO was mainly dominated by [111] texture with an optical band gap of approximately 3.69 eV. Compared with the conventional Ni/GaN photodetector, the p-NiO/GaN heterostructure photodetector possess a larger turn-on voltage and a smaller dark current because of the relatively higher effective barrier height. At an external bias of 0 V, the photo responsivity and the UV to visible rejection ratio of the NiO/GaN photodetector are enhanced to 0.15 A/W and 406, respectively. The improvement in UV photodetector performance is attributed to that the depletion region in NiO/GaN heterostructure can effectively eliminate the trapping charge carriers at the metal/semiconductor interface. The high-performance NiO/GaN photodetectors without driving power are potential for portable UV detectors application.