Influence of Schottky metal-semiconductor contact on the responsivity of UV photodetectors with internal gain

Metal-semiconductor-metal (MSM) ultraviolet photodetector is fabricated on ZnO films, prepared by radio frequency magnetron sputtering technique on quartz substrates. The ZnO photodetector shows low dark current and external quantum efficiency (EQE) due to the gain effect. The device also exhibits a near linear responsivity dependence on voltage, which gradually rise to the peak first, then fall sharply, and then slightly rise again. A physical mechanism primarily focused on the relationship between carrier (electron-hole pairs) transport and barrier height at Schottky metal-semiconductor contact is given to explain the above phenomena. It is demonstrated as a straightforward and convenient way to enhance the internal gain of the simple ZnO-based Schottky photodetectors for application in the future.