Effect of enhanced-mobility current path on the mobility of AOS TFT

In this study, the mobility enhancement in an Amorphous Oxide Semiconductor Thin Film Transistor (AOS TFT), particularly the effect of enhanced-mobility current path was investigated. In the TFT structure, the a-IGZO single active channel layer was replaced by double layers. Indium Tin Oxide (ITO) was employed as an enhanced-mobility current path material and was embedded in an amorphous Indium Gallium Zinc Oxide (a-IGZO) channel layer of a conventional bottom gate structure TFT. To analyze the effect of the length of an additional current path, the a-IGZO channel length was fixed at 80 μm, and the length of the ITO enhanced-mobility current path was increased to 20, 40, and 60 μm. As a result, the mobility increased monotonically with the length of the enhanced-mobility current path and was predictable from the rule of mixture. The maximum saturation mobility of 28.3 cm²/V s resulted when the length of the enhanced-mobility current path was 60 μm. This value is more than double that of a single path TFT. Such enhancement in mobility is attributed to the high conductivity of ITO and a good conduction band match between a-IGZO and ITO.