Dependence of channel thickness on the performance of In₂O ₃ thin film transistors

Bottom gate and top contact thin film transistors were fabricated using In₂O₃ thin films as active channel layers. Thin films of varying thicknesses in the range 5-20 nm were deposited on an SiO₂ gate dielectric by the thermal evaporation process in the presence of high purity oxygen. The results of atomic force microscopy show that all the films exhibit dense grain distribution with a root-mean-square roughness in the range 0.6-8.0 nm. Irrespective of the thickness of the channel layer, the on/off ratio of the device is 10⁴. The channel mobility and resistivity were found to be a strong function of the thickness of the active layer. The Levinson model was used to calculate the trap density and the grain boundary mobility. The low processing temperature shows the possibility of utilizing these devices on flexible substrates such as polymer substrates.