Improved Performance of InGaZnO Thin-Film Transistor With Ti Incorporation Into La2O3 Gate Dielectric

The effects of Ti incorporation in La2O3 gate dielectric on the electrical characteristics of amorphous InGaZnO thin-film transistor are studied. Compared to the control sample with La2O3 gate dielectric, the device performance can be significantly improved with an appropriate Ti dose. Accordingly, the sample with a Ti/(Ti+La) ratio of 6.7% presents a high saturation mobility of 28.1 cm2V−1s−1, small subthreshold slope of 0.17 V/dec, large on/off current ratio of $7.2\times 10$ 7, and acceptable hysteresis. We attribute such an improvement to the passivation of the defect states at/near the La2O3/InGaZnO interface as well as the enhancement of moisture resistance of La2O3 film due to Ti incorporation. However, excessive Ti incorporation leads to device degradation, which is due to more oxygen vacancies generated in gate dielectric.