Effect of the Hydrophobicity of Hybrid Gate Dielectrics on a ZnO Thin Film Transistor

Amorphous silicon thin film transistors (a-Si TFTs) are widely used for consumer electronics and have been demonstrated to be useful for use in solar cells and flexible displays. Organic thin film transistors are of interest for applications in low-cost electronic devices such as radio-frequency identification tags, flexible displays, memory and sensors. However, the applications of these devices are limited by their low mobility and light/ moisture sensitivity due to intrinsic material properties Recently, zinc oxide (ZnO) has drawn much attention as one of the promising II-VI compound semiconductors that exhibits a wide band gap of 3.35 eV and a wurtzite structure; it can be used to form transparent electrodes, gas sensors, photovoltaic devices, light emitters, and bulk acoustic wave devices [1]. ZnO TFTs prepared by different techniques have been reported previously, mostly using inorganic dielectrics such as aluminum oxide [2-6]. The use of organic dielectrics for TFTs is likely to be an ideal solution for all-organic electronics. However, there have been few reports on oxide semiconductors used with a polymeric gate dielectric produced by atomic layer deposition (ALD) technology before the recent report [7]. In the case of organic gate dielectrics, the threshold voltage shift and hysteresis behaviors are unstable due to their structural imperfections and moisture absorption. In order to find a suitable dielectric system, polymer and high-k oxide double layer dielectrics could be used for TFT applications. In this work, a bottom-gate and bottom-contact ZnO TFT prepared from ALD with a polymeric dielectric and silicon oxide hybrid materials was fabricated in order to investigate the effect of the hydrophobocity of the gate insulator on the TFT properties. The hysteresis behavior of this TFT was examined.