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

The dynamic response of amorphous In-Ga-ZnO (a-IGZO) thin-film transistors (TFTs) are compared with hydrogenated amorphous silicon (a-Si:H) TFTs. We study the storage capacitor (Cst) charging characteristics by applying gate and data voltage waveforms for ultra-high definition (UHD) active-matrix flat-panel displays (AMFPDs). Experimental data show that the charging characteristics of a-Si:H TFTs is clearly inadequate for UHD AM-FPDs and that a-IGZO TFTs are at least capable of supporting up to 8K×4K resolution at 480 Hz. The impact of the gate voltage falling edge on feedthrough voltage (ΔVP) is investigated in detail. Although for the same Cst the ΔVP is larger for a-IGZO TFT than a-Si:H TFTs, Cst of the a-IGZO TFT can be made larger to reduce ΔVP without obvious degradations in charging behavior. Gate overdrive operation is also demonstrated for a-IGZO TFTs to improve charging characteristics without visible impact on ΔVP. Our results show that the a-IGZO TFT is a suitable technology for next-generation UHD high-frame rate AM-FPDs.