Samsung Advanced Institute of Technology

Amorphous oxide semiconductors have been widely studied for various applications, including thin-film transistors (TFTs) for display backplanes and semiconductor memories. However, the inherent instability of amorphous structures and the complexity of multicomponent oxide semiconductors for achieving high aspect ratios and uniformity remain challenging. Here, we firstly propose a c-axis aligned composite (CAAC) indium-zinc oxide (IZO) with superior TFT properties, including a remarkable performance of field-effect mobility (μ_FE) of 55.8 cm²/Vs and positive-bias-temperature-stress stability of +0.16 V (2 MV/cm, 60 °C, 1 h), as well as low subthreshold swing as 0.18 V/decade and hysteresis as 0.01 V could be obtained through optimization of growth temperature and composition using thermal atomic layer deposition. Nanocrystal-embedded amorphous indium-rich IZO and polycrystalline zinc-rich IZO-based TFT exhibit significantly degraded performances. In addition, an amorphous IZO exhibited inferior mobility and stability even at a composition identical to that of the proposed CAAC-IZO. Finally, excellent conformality and step coverage (97 %) of IZO is identified on 40:1 trench structure. Our results include a detailed investigation of the influence of the crystal structure of IZO on the film and TFT performance and suggest an approach for the future applications.