Crystallographic Alignment Reshapes the Electronic Landscape and Enhances Charge Transport in Indium Gallium Oxide Thin‐Film Transistors

Amorphous indium gallium zinc oxide thin-film transistors are widely used in high-end organic light-emitting diode displays. However, their intrinsic mobility-stability trade-off fundamentally limits further performance scaling. Crystallized oxide semiconductors have emerged as a promising pathway to overcome this constraint, yet the relative roles of crystallinity and crystallographic alignment remain unclear. Here, we systematically compare amorphous, random-polycrystalline, and highly aligned crystalline indium gallium oxide channels to elucidate the origin of enhanced charge transport. Temperature-dependent electrical analysis and multi-frequency capacitance-voltage spectroscopy reveal that crystallographic alignment sharpens and energetically stabilizes subgap states near the conduction band, indicating reduced energetic disorder. Spatially resolved potential analysis further shows that this alignment suppresses grain-boundary-induced potential barriers, producing a more uniform transport landscape. In contrast, random-polycrystalline channels retain broadened subgap states and spatially distributed grain-boundary barriers despite their crystallinity. These results show that crystallographic alignment, rather than crystallinity alone, governs charge transport in polycrystalline oxide semiconductors by concurrently optimizing the energetic and spatial aspects of the electronic landscape, while maintaining robust bias-stress stability.