Structural and electrical properties of high-κ CeTixOy, ErTixOy and YbTixOy gate dielectrics for InZnSnO thin film transistors

The structural properties and electrical characteristics of high-κ CeTixOy, ErTixOy and YbTixOy gate dielectrics for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) were investigated in this paper. We employed X-ray diffraction to determine the material phase and crystallinity, atomic force microscopy to examine the surface morphology of the dielectric films, and X-ray photoelectron spectroscopy to analyze the chemical feature of three films. The IZTO TFT incorporating a YbTixOy gate dielectric exhibited better electrical characteristics, such as a low threshold voltage (VTH) of 0.17 V, a large field-effect mobility of 20.8 cm2/V-s, a high Ion/Ioff ratio of 3 × 108, and a low subthreshold slope of 108 mV/decade, in comparison with those of other dielectrics. This result suggests that the YbTixOy dielectric possesses a smoother surface as well as a lower oxygen vacancy (or defect). Moreover, the VTH stabilities of IZTO TFT devices were investigated for positive bias stress and negative bias stress conditions.