Layer-Selective Crystallization of Indium–Gallium Oxide and Indium–Gallium–Zinc Oxide Bilayer Channel Induced by Annealing After UV Treatment for High-Performance Oxide Thin-Film Transistors

A bilayer channel, consisting of crystalline indium-gallium oxide (IGO) and amorphous indium-gallium-zinc oxide (IGZO), was engineered with annealing after ultraviolet (AAU) treatment to simultaneously enhance mobility and stability of oxide thin-film transistors (TFTs). The formation of an ordered crystalline IGO layer and a dual conduction channel facilitates carrier transport, while the rearrangement of metal-oxygen bonds suppresses oxygen-related defects, collectively leading to improved electrical performance. As a result, the AAU-treated IGO/IGZO TFT exhibited field-effect mobility (μ_FE) of 42.39 cm²/V·s, subthreshold swing (S.S.) of 0.42 V/decade, on/off current ratio of 1.01 × 10⁸, and threshold voltage (<i>V</i>_TH) of 0.71 V. In terms of bias stability, under positive bias stress, negative bias stress, and negative bias illumination stress tests, <i>V</i>_TH shifts of +3.28, -0.15, and -2.22 V were observed, respectively.