Abstract
Abstract The technological advancement of liquid crystal displays (LCDs) is changing with time everyday. Recently, it has started to dominate the display devices in a large scale and this has urged for more technological improvement. One challenging area for the electronics industry is the development of fully transparent optoelectronics devices. Substituting thin film transistors (TFTs) made of amorphous Si (a-Si) or polycrystalline Si (poly-Si) that are currently used in active-matrix liquid crystal displays (AMLCDs) with transparent ZnO-TFTs would enable improvement in the opening of pixels, resulting in a reduction in power consumption and avoidance of complicated device processing. In addition to that it would result in an all transparent electronics device. The objective of the present thesis is to fabricate a highly transparent TFT device, with a focus on ZnO-TFT. ZnO has become an attractive wide band gap semiconductor since the demonstration of ultraviolet laser action at room temperature. ZnO can be used as an active channel layer for the realization of transparent thin-film transistors (TTFTs). In this work bottom-gate-type thin film transistors using ZnO as an active channel layer (ZnO–TFT) have been constructed. The ZnO layers were deposited using rf magnetron sputtering at 300 °C at a working pressure of 30mTorr. A double layer gate insulator consisting of SiO2 and SiNx was effective in suppressing leakage current and enabling the ZnO–TFT to operate successfully. The optical transmittance of ZnO–TFTs fabricated on glass was more than 70% in the visible portion of the electromagnetic spectrum. The prototypical n-channel, depletion mode TFT characteristics, and these results show that it is possible to fabricate a transparent TFT that can even be operated in the presence of visible light. We believe that the consumer application will be further evolved widely based on this development.