Impact of Interfacial Trap Density of States on the Stability of Amorphous InGaZnO-Based Thin-Film Transistors

The impact of interfacial trap states on the stability of amorphous indium-gallium-zinc oxide thin film transistors is studied under positive gate bias stress. With increasing stress time, the device exhibits a large positive drift of threshold voltage while maintaining a stable sub-threshold swing and a constant field-effect mobility of channel electrons. The threshold voltage drift is explained by charge trapping at the high-density trap states near the channel/dielectric interface, which is confirmed by photo-excited charge-collection spectroscopy measurement.