Semi-transparent UV-detecting ZnO-TFTs with polymer gate dielectric

We report on the fabrication of ZnO-based ultraviolet (UV)-detecting thin-film transistors (TFTs) with a semitransparent conducting NiO_x 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 cm²/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/cm²). The on/off current ratio of the device was about 103. However, the current increased up by more than 30 times with UV illumination of 325 nm wavelength (power density ∼50 μW/cm²) 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. copyright The Electrochemical Society.