Improved electrical characteristics of amorphous InGaZnO thin-film transistor with HfLaO gate dielectric by nitrogen incorporation

A comparative study on the electrical characteristics of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with HfLaO and HfLaON gate dielectrics is conducted. With the appropriate incorporation of nitrogen into the HfLaO gate dielectric, the saturation mobility of the TFTs can reach 31.3 cm2 V−1 s−1, which is more than twice that of the control sample with the HfLaO gate dielectric, as a result of the passivation of traps at/near the dielectric/a-IGZO interface by the nitrogen incorporation. However, the electrical characteristics (such as saturation mobility, on-current, and on-current/off-current ratio) of the devices tend to deteriorate with excessive nitrogen incorporation owing to nitrogen-related defects generated in the dielectric.