Influence of Passivation Layers on Positive Gate Bias-Stress Stability of Amorphous InGaZnO Thin-Film Transistors.

Yan Zhou,Chengyuan Dong

doi:10.3390/mi9110603

Abstract

Passivation (PV) layers could effectively improve the positive gate bias-stress (PGBS) stability of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs), whereas the related physical mechanism remains unclear. In this study, SiO2 or Al2O3 films with different thicknesses were used to passivate the a-IGZO TFTs, making the devices more stable during PGBS tests. With the increase in PV layer thickness, the PGBS stability of a-IGZO TFTs improved due to the stronger barrier effect of the PV layers. When the PV layer thickness was larger than the characteristic length, nearly no threshold voltage shift occurred, indicating that the ambient atmosphere effect rather than the charge trapping dominated the PGBS instability of a-IGZO TFTs in this study. The SiO2 PV layers showed a better improvement effect than the Al2O3 because the former had a smaller characteristic length (~5 nm) than that of the Al2O3 PV layers (~10 nm).

Highlights

Amorphous InGaZnO thin-film transistors (a-IGZO TFTs) have considerable potential for applications in next-generation flexible, transparent, and large-size flat panel displays (FPDs) because of their superior electrical characteristics, such as large field-effect mobility (~10 cm2/V·s), low subthreshold swing (~0.2 V/decade), small leakage current (
The reliability issues, e.g., threshold voltage (Vth) shift under positive gate bias stress (PGBS), remain to be solved. Both charge trapping [3,4,5,6] and ambient atmosphere effect [7,8,9,10,11,12,13,14] have been reported to be responsible for Vth shifts in amorphous InGaZnO (a-IGZO) TFTs during PGBS tests
PGBS instability may seriously hinder the actual applications of a-IGZO TFTs in FPDs because it may directly impact the brightness uniformity and stability of display panels

Summary

Introduction

Amorphous InGaZnO thin-film transistors (a-IGZO TFTs) have considerable potential for applications in next-generation flexible, transparent, and large-size flat panel displays (FPDs) because of their superior electrical characteristics, such as large field-effect mobility (~10 cm2/V·s), low subthreshold swing (~0.2 V/decade), small leakage current (

Materials and Methods

Conclusions