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

The dynamic response of hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) and amorphous In-Ga-Zn-O (a-IGZO) T
_FT
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
_FT
is insufficient for UHD AM-LCDs and that the a-IGZO T
_FT
is capable of supporting at least 8 K ×4 K display resolution at 480 Hz. The impact of C
_st
and gate voltage falling edge (t
_FE
) on feedthrough voltage (ΔV
_P
) is investigated. Because of higher mobility of the a-IGZO T
_FT
, it is possible to reduce ΔV
_P
by mitigating channel charge redistribution with non-abrupt tFE. The a-IGZO TFT shows no drawbacks in terms of ΔV
_P
when compared to the a-Si:H T
_FT
. In addition, a larger C
_st
can be used in combination with the a-IGZO T
_FT
to reduce ΔV
_P
with minimal impact on its charging behavior. Gate overdrive operation is also evaluated for the a-IGZO T
_FT
, which may improve charging characteristics with no adverse effects on ΔV
_P
. Our results show that the a-IGZO T
_FT
is a suitable technology for UHD high-frame rate AM-LCDs.