Advances in Zinc Oxide-Based Devices for Active Matrix Displays

Metal oxides have been proposed as an alternative channel material to hydrogenated amorphous silicon in thin film transistors (TFTs) because their higher mobility and stability make them suitable for transistor active layers. Thin films of indium zinc oxide (IZO) were deposited using a High Target Utilization Sputtering (HiTUS) system on various dielectrics, some of which were also deposited with the HiTUS. Investigations into bottom-gated IZO TFTs have found mobilities of 8 $cm^2V\;^1s^{-1}$ and switching ratios of $10^6$. There is a variation in the threshold voltage dependent on both oxygen concentration, and dielectric choice. Silica, alumina and silicon nitride produced stable TFTs, whilst hafnia was found to break down as a result of the IZO.