Channel engineering of ZnO-based thin film transistors using Al2O3 interlayer grown by atomic layer deposition

Abstract

In this study, an Al2O3 interlayer is grown between the ZnO channel layer and the gate dielectric by atomic layer deposition to improve the electrical characteristics of ZnO-based thin film transistors (TFTs). From the current–voltage measurements, superior electrical performance characteristics are confirmed, such as superior subthreshold swing and on-/off-current ratio. On the basis of the results of X-ray diffraction (XRD) analysis, the enhanced properties can be explained by large grains in the ZnO channel layer that is deposited on Al2O3. However, when ZnO grains are aligned in the (002) direction, the stability characteristics under positive bias stress become inferior, which is considered to be caused by considerable oxygen adsorption at the nonpassivated channel surface owing to Zn polar extension.