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

Abstract

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 80μm, and the length of the ITO enhanced-mobility current path was increased to 20, 40, and 60μm. 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 28.3cm2/Vs resulted when the length of the enhanced-mobility current path was 60μm. 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.