Hybrid visible-blind ultraviolet photodetector based on NiO thin-film phototransistor and p-NiO/n-Si heterojunction diode

Abstract

A hybrid visible-blind ultraviolet (UV) photodetector, which combines a p-NiO/n-Si heterojunction diode and NiO-based thin-film phototransistor, was proposed, and its optoelectronic properties were studied. The hybrid photodetector exhibited a high quantum efficiency and photocurrent gain. The p-NiO/n-Si heterojunction separates the photogenerated electron–hole pairs, thereby reducing the recombination probability of the electron–hole pairs and enhancing photocurrent gain. In the hybrid photodetector, the ratio of the photo current to dark current (IP/ID) increased with an increase in the drain source voltage (VDS) because more photogenerated holes were extracted. Responsivity decreased with increasing positive gate voltage (VG) owing to the depleted channel layer. Conversely, the responsivity increases with increasing negative VG because more holes are accumulated at the surface of the NiO channel layer. The UV (280 nm)/visible (500 nm) rejection ratio is as high as 700–850, indicating that the prepared hybrid device is a good visible-blind photodetector. Detectivity increased from 6.72 × 1012 to 2.23 × 1013 Jones by decreasing VG from 10 to −10 V. Band diagrams of p-NiO/n-Si heterojunction diodes and NiO-based thin-film phototransistors were proposed to elucidate the mechanism of the photocurrent gain in the prepared hybrid photodetector.