Dynamic Response of a-InGaZnO and Amorphous Silicon Thin-Film Transistors for Ultra-High Definition Active-Matrix Liquid Crystal Displays

Abstract

The dynamic response of hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) and amorphous In-Ga-Zn-O (a-IGZO) T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> are compared. We study the storage capacitor (Cst) charging characteristics by applying gate and data voltage waveforms corresponding to ultra-high definition (UHD) active-matrix liquid crystal displays (AM-LCDs). We show that the charging behavior of the a-Si:H T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> is insufficient for UHD AM-LCDs and that the a-IGZO T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> is capable of supporting at least 8 K ×4 K display resolution at 480 Hz. The impact of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sub> and gate voltage falling edge (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FE</sub> ) on feedthrough voltage (ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> ) is investigated. Because of higher mobility of the a-IGZO T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> , it is possible to reduce ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> by mitigating channel charge redistribution with non-abrupt tFE. The a-IGZO TFT shows no drawbacks in terms of ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> when compared to the a-Si:H T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> . In addition, a larger C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sub> can be used in combination with the a-IGZO T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> to reduce ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> with minimal impact on its charging behavior. Gate overdrive operation is also evaluated for the a-IGZO T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> , which may improve charging characteristics with no adverse effects on ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> . Our results show that the a-IGZO T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</sub> is a suitable technology for UHD high-frame rate AM-LCDs.