Effects of continuous annealing on the performance of ZnO based metal-semiconductor-metal ultraviolet photodetectors

In this study, metal-semiconductor-metal (MSM) Schottky ultraviolet (UV) photodetectors were based on c-axis preferred oriented zinc oxide (ZnO) films, which were prepared on quartz substrates by radio frequency (RF) magnetron sputtering technique. The responsivity of the photodetector was enlarged greatly after annealing the MSM device. Meanwhile, the enhancement in the dark current that resulted from the experiment was accompanied by the increasing annealing temperature. The origin is preliminarily discussed combining the observations of dark currents and responsivities. The physical mechanism of the continuous annealing is proposed on the basis of metal-semiconductor contact theory and diffusion effect. By this model, Au atoms from the electrode play an important role in the Schottky barrier during annealing process. These results demonstrate that a simple route to improve the responsivities of photodetectors can be realized easily by annealing the devices.