Improved Performance and Operational Stability of Solution-Processed InGaSnO (IGTO) Thin Film Transistors by the Formation of Sn–O Complexes

Solution-processed indium gallium tin oxide (InGaSnO, IGTO) thin film transistors (TFTs) are investigated as promising low-cost and stable materials for high-performance amorphous oxide semiconductor (AOS)-based TFTs in display applications. After tailoring the metal cation composition in IGTO thin films, the IGTO (7:1:1) AOS TFT shows a saturation mobility and current on/off ratio of 2.13 cm² V^–1 s^–1 and 2.55 × 10⁷, superior to the IGZO TFT. It was found that the threshold voltage (V_th) shifts of IGTO TFTs with higher Sn molar ratios became gradually diminished both under the positive bias stress (PBS) test, from +7.3 to +1.1 V, and under the negative bias stress (NBS) test, from −2.83 to −0.94 V, due to the increased concentration of Sn–O complexes with relatively higher bonding energies within IGTO thin films. X-ray photoelectron spectroscopy (XPS) analysis also reveals that IGTO thin films with higher Sn composition ratio tend to effectively suppress the formation of oxygen vacancy, which consequently led to the improved stability of IGTO-based TFTs under the gate bias stress. Therefore, these results can be the basis for improving the characteristics of IGTO semiconducting channel systems for low-cost switching devices in the display applications.