Binary response Se/ZnO p-n heterojunction UV photodetector with high on/off ratio and fast speed

A high-performance UV photodetector (PD) based on a p-Se/n-ZnO hybrid structure with large area (more than 1x1 cm) is presented in this study. The device is theoretically equivalent to a parallel-connection circuit for its special structure and shows multifunction at different voltage bias, which means the output signal can be tailored by an applied voltage. The Se/ZnO PD shows binary response (positive and negative current output under on/off periodical light illumination) under small reverse bias (-0.05 V and -0.1 V) which efficiently reduces the negative effect of noise signal in weak-signal detection applications. At zero bias, with the aid of a p-n heterojunction, a high on/off ratio of nearly 10(4) is achieved by this device at zero set bias under 370nm (approximate to 0.85 mW cm(-2)) illumination and this on/off ratio can be achieved in 0.5 s. The device also shows a fast speed with rise time of 0.69ms and decay time of 13.5ms measured by a pulse laser, much faster than that of a pure ZnO film. The Se/ZnO PD in this research provides a new pathway to fabricate multifunctional high-speed, high signal-to-noise ratio, high detectivity and high selectivity UV photodetectors.