Solution-processed stacked TiO2 and Al2O3 dielectric layers for high mobility thin film transistor

In this paper, a TiO2/Al2O3/TiO2/Al2O3/TiO2 (TATAT) stacked structure was developed as a gate dielectric for amorphous ZnSnO (ZTO) thin-film transistor (TFT) applications. The TATAT insulator has a relative permittivity and leakage current density of 11 and 4.44 × 10-7 A/cm2 at 1 MV/cm, respectively. As compared with the AlTiO (ATO) compound dielectric, the ZTO TFT device with a TATAT stacked dielectric exhibited a lower threshold voltage of 0.56 V, a higher Ion/Ioff current ratio of 1.2x 10-8, a larger field-effect mobility of 86.6 cm2/Vs, and a smaller subthreshold swing of 0.2 V/decade. Furthermore, the positive shift of threshold voltage is less than 0.15 V under positive bias stress. The results suggest that stack TATAT films is a promising gate dielectric for solution-processed TFT devices with high mobility and stability.