Amorphous In-Ga-Zn-O Thin-Film Transistor for High Resolution Active Matrix Flat Panel Displays and Imagers.

Abstract

There is considerable interest in adapting amorphous Indium-Gallium-Zinc-Oxide thin-film transistors (a-IGZO TFTs) in such applications as active matrix flat panel displays (AM-FPDs) and imagers (AM-FPIs), because of their high mobility in the amorphous phase, low off-current and suitability for low temperature fabrication. So far much of the research efforts on a-IGZO TFTs have been focused on improving the a-IGZO material properties as well as the gate dielectric/a-IGZO interface. However, the electrical performance of TFTs is also influenced by the TFT structures. In this study, the characteristics of the double gate (DG) coplanar homojunction a-IGZO TFTs are investigated. The coplanar homojunction a-IGZO TFT has a good ohmic source/drain junction. With DG structure, a high on-current and steep subthreshold swing are achieved without any changes in the off-current by applying the same voltage on the bottom and top gates. The dynamic control of TFT's threshold voltage is also demonstrated by applying various voltages on the top gate. To explain these phenomena, analytic models of DG a-IGZO TFTs are developed based on device physics. Furthermore, this study shows that the illumination and bias-temperature stabilities are enhanced in comparison to traditional single gate a-IGZO TFTs. The superior electrical properties and stability of the DG a-IGZO TFT make it possible strong candidates for use in pixel circuits of future high resolution AM-FPDs and AM-FPIs.