A Unified Mechanism for Strain- and Anneal-Induced Oxygen-Vacancy Behavior in Oxide Semiconductors

High Resolution Image Download MS PowerPoint Slide Oxygen vacancies ( V O ) critically influence the electrical performance and reliability of amorphous oxide semiconductor (AOS) devices, including indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs). Using first-principles density functional theory and configuration-coordinate analysis, we elucidate a unified mechanism connecting the contrasting behaviors of V O under strain versus annealing. We demonstrate that both mechanical strain and annealing-induced structural relaxation modulate the energetic position and localization character of V O states by altering specific interatomic distances. Compressive strain shortens key metal–metal separations, thereby stabilizing bonding-like localized states, lowering their formation energy, and driving a delocalized-to-localized transition; conversely, tensile strain induces the opposite trend. Along the structural-relaxation pathway, the defect level shifts upward toward the conduction band minimum as critical distances increase, promoting delocalization. Ab initio molecular dynamics simulations further corroborate that higher thermal budgets facilitate this relaxation, thereby enhancing donor activation. Crucially, we resolve the prevailing apparent strain–annealing densification inconsistency: annealing-induced delocalization arises not from increased mass density (as in compressive strain), but specifically from structural relaxation that expands critical interatomic distances and minimizes screened ion–ion repulsion. These findings provide a rigorous atomistic framework for manipulating defect states via strain engineering and thermal processing, offering precise guidelines for optimizing the stability and performance of next-generation AOS electronics.