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

The effects of Ti incorporation in La
₂
O
₃
gate dielectric on the electrical characteristics of amorphous InGaZnO thin-film transistor are studied. Compared to the control sample with La
₂
O
₃
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 cm
²
V
⁻¹
s
⁻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 La
₂
O
₃
/InGaZnO interface as well as the enhancement of moisture resistance of La
₂
O
₃
film due to Ti incorporation. However, excessive Ti incorporation leads to device degradation, which is due to more oxygen vacancies generated in gate dielectric.