Semi-transparent UV-Detecting ZnO-TFTs with Polymer Gate Dielectric

Abstract

We report on the fabrication of ZnO-based ultraviolet (UV)- detecting thin-film transistors (TFTs) with a semitransparent conducting NiOx top-gate electrode window and 450 nm-thick poly-4-vinylphenol (PVP) gate dielectric layer that has been formed on n-ZnO by spin-casting. The field effect electron mobility of our device was only about 0.0032 cm^2/Vs at the saturation regime of gate bias showing a low saturation current level in the dark because the PVP dielectric has a relatively low dielectric capacitance (7.4 nF/cm^2). The on/off current ratio of the device was about 10^3. However, the current increased up by more than 30 times with UV illumination of 325 nm wavelength (power density ~0.05mW/cm^2) while the initial current level was not varied with visible green illumination. We conclude that our ZnO-TFT with organic gate dielectric can be a promising transparent UV-detecting device.