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 cm 2 /V·s, subthreshold swing (S.S.) of 0.42 V/decade, on/off current ratio of 1.01 × 10 8, and threshold voltage ( V TH ) of 0.71 V. In terms of bias stability, under positive bias stress, negative bias stress, and negative bias illumination stress tests, V TH shifts of +3.28, −0.15, and −2.22 V were observed, respectively.