Research Of ZnO Based Thin Film Transistors And Amorphous Transparent Conductive Films

Zinc Oxide (ZnO) is considered as a promising material for the channel of thin film transistors ((TFTs) because of its high mobility and low temperature process. Meanwhile, ZnO not only can be easily heavily doped for electrode applications, but also can be combined with other oxides to form multi-component amorphous conducting oxide to adjust its band gap and work function. In this thesis, our research focused on two different parts:1. We fabricated thin film transistors with ZnO as the channel layer and focused on the ultraviolet photoresponse of the transistors.2. We aimed at how to get ZnO based amorphous TCOs with good performance. The major contents of this thesis are summarized as follows:1. Magnetron sputtering was adopted to grow ZnO channel layer of the thin film transistor and the ZnO-TFTs have good ultraviolet response characteristic. As to output characteristic, the saturation current under365and254nm illumination were almost three and six times higher than the maximum value in the dark. After the UV light is turned off, the rate of on-state current decay more slowly than off-state current due to the effect of gate bias voltage.2. Amorphous InAlZnO films were fabricated by pulse laser deposition technique, and their performance was improved by optimizing the deposition parameters and chemical composition or employing a metal layer sandwiched by TCOs.(1) With the increase of growth temperature, the resistivity of the films first dropped dramatically and then decreased slowly when the temperature was over300℃. As the oxygen pressure increased, the carrier concentration began to decrease, which is not benefit for the improvement of electrical performance. The optimized oxygen pressure is0.01Pa. As the deposition time prolong, the film became thicker and got better electrical performance, but the optical transmittance decline greatly.(2) As the content of Al increased, both of the carrier concentration and mobility decreased. When the content of Al arrived at6.4at.%, the electrical properties of the films became worse slightly, but their surface became smoother as the crystallinity got worse.(3) Compared to InAlZnO films, no matter for Cu/InAlZnO or InAlZnO/Cu/InAlZnO, the conductivity of films would decrease obviously. But the thickening of the Cu layer will lead to the decrease of transmittance in the visible range and thus the deterioration of overall performance.