Metal-metal bond-induced conduction band reshaping drives performance degradation in short-channel amorphous In-Ga-Zn-O thin-film transistors

Amorphous In-Ga-Zn-O (a-IGZO) semiconductor has shown broad application prospects due to its high electron mobility which is comparable to its crystal counterpart. However, the complex atomic bonding environment within the material continues to plague the stability of carrier transport. Here, we propose a quantum flow to simulate oxygen-related defect behaviors in a-IGZO from material to device application. The results reveal that both oxygen interstitial (O i ) and vacancy (V O ) defects dynamically capture or release electrons by sudden structure relaxations (bond formation or broken) in response to environmental electron concentration changes, forming a negative feedback mechanism. In comparison, O i -induced oxygen–oxygen bonds rarely create trap states within the bandgap, while V O -induced metal–metal (M–M) bonds generate trap states spanning the upper half of the bandgap. Crucially, we demonstrate that M–M bonds severely impede electron transport through a mechanism unrelated to trap levels—instead, they induce local conduction band reshaping. Transport simulations indicate that the transport degradation caused by a single M–M bond is comparable to the effect of strong conduction band minimum fluctuation across the entire channel, with this impact further amplified as channel length decreases. Our work suggests that moderately increasing oxygen content and decreasing the n -doping level could mitigate this issue in a-IGZO thin-film transistors. • M–M bonds reshape conduction band in a-IGZO. • Band distortion, not traps, limits transport. • Vacancy induces M–M bonds with deep impact. • Local defect mimics global band fluctuation. • Short-channel TFTs more vulnerable to M–M.