Modeling the Increase in Effective Mobility in Short-Channel Oxide Thin-Film Transistors

This paper investigates the dependence of effective carrier mobility on the channel length in oxide thin-film transistors (TFTs). Bottom-gate staggered TFTs fabricated with a sputtered indium-gallium-zinc-oxide channel exhibit a substantial increase in field-effect mobility with decreasing channel length, which is at variance with typical manifestation of contact resistance. An original model is thus proposed to describe the channel-length-dependent mobility in these TFTs. By decoupling local and intrinsic transport properties affecting the drain current, the model reproduces and rationalizes the observed phenomena. These results provide both a practical modeling tool and fundamental insights into the behaviors of oxide TFTs associated with the charge injection at their metal/semiconductor interface.