Physical Insights Into the Mobility Enhancement in Amorphous InGaZnO Thin-Film Transistor by SiO2 Passivation Layer

For the first time, the mobility enhancement mechanism due to the SiO2passivation layer (PVL) in amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) is studied using technology-computer-aided design (TCAD) simulation. Our results indicate that the introduction of oxygen vacancies in shallow donor states around the PVL/a-IGZO interface, which donate more free electrons in the induced accumulation layer of the channel, increases the field-effect mobility of the TFT by 5.7×. Results of our TCAD simulations are strongly supported by X-ray photoelectron spectroscopy (XPS) measurements. Furthermore, TCAD analysis of a three-stage ring oscillator composed of the sample with PVL indicates 27-MHz oscillation frequency is possible at 10-V supply voltage.