All-Transparent Zinc Oxide-Based Phototransistor by Mist Atmospheric Pressure Chemical Vapor Deposition

This letter demonstrates an all-transparent ZnO-based phototransistor on which fluorine-doped tin oxide, magnesium oxide, zinc oxide, and aluminum-doped zinc oxide thin films are deposited by mist atmospheric pressure chemical vapor deposition. This phototransistor is designed for ultraviolet detection and can be illuminated from either the front or backside. By comparing the device characteristics, the backside illumination exhibits better performance. The phototransistor is able to be operated in high ultraviolet-to-visible rejection ratio/fast response mode. In this mode, the ultraviolet-to-visible rejection ratio reaches 2915 and the rising/decay time of 5.35/6.8 s are achieved. The second mode is high responsivity/detectivity mode. In this mode, responsivity of 2520 A/W, photoconductive gain of 8682, and detectivity of $\textsf {1.57}\times \textsf {10}^{\textsf {11}}$ cm-Hz-W –1 are obtained. It is also found that the operation mode is controlled by the gate bias.