Evolution of Defect Structures and Deep Subgap States during Annealing of Amorphous In-Ga-Zn Oxide for Thin-Film Transistors

Abstract

Amorphous indium gallium zinc oxide ($a$-IGZO) has drawn considerable interest as a channel material in flexible thin-film transistors (TFTs), to replace amorphous-Si-based TFTs, but $a$-IGZO-based TFTs show environment-dependent instability in threshold voltage. Investigating the variation of defect structures and subgap states with post-annealing temperature, this study reveals that the excess oxygen atoms surrounding cations or cation-vacancy-related defect clusters give rise to the instability. These results open a route to understanding the physical origin of device instability, and offer a feasible approach to tailoring such defects for practical applications.