Comparative Study of Short-Channel Effects between Source-Gated Transistors and Standard Thin-Film Transistors

With the development of virtual reality and augmented reality, the pixel sizes of displays are reaching the sub-micron regime. One of the main challenges is the short-channel effect of the thin-film transistors in the driving circuits. In this work, we report the short-channel effects of indium-gallium-zinc-oxide source-gated transistor (IGZO SGT). The simulation results show that when reducing the channel length down to 500 nm, the output impedance of the IGZO SGT is still high up to 4.13×108 Ωμm at gate-source voltage (VGS) of 5 V and drain-source voltage (VDS) of 7 V, 437 times higher than that of a conventional IGZO thin-film transistor (TFT) of the same dimension. It is found that the Schottky source contact in SGTs can effectively suppress the back-channel current as compared with TFTs. The threshold voltage of short-channel SGTs remains almost the same when applying different drain voltages in contrast to TFTs. When VDS changes from 5 to 7 V at VGS = 5 V, the drain current of the IGZO TFT increases 23.7%, while the drain current of the SGT only increases 0.8%. The experimental results of IGZO TFTs and SGTs with a channel length of 500 nm showed similar dependence on the drain voltage to the simulation results. Such insensitivity to short-channel effects makes SGTs a promising candidate as current driving transistors in high-pixel-density display circuits.