Interface Defect Shielding of Electron Trapping in a-InGaZnO Thin Film Transistors

In this work, an abnormal lowering of subthreshold swing (SS) after self-heating stress in a device with thick channel is observed. A model of interface defect shielding is proposed, based on electron trapping at the channel/gate insulator interface. The phenomenon is discussed systematically through the band diagram and extractions of the field effective mobility. Results suggest that a depletion region appears after electron trapping at the front channel, which then prevents the carriers from reaching the interface defects. Therefore, an abnormal superior electrical performance after stress is observed. Finally, a dual gate amorphous InGaZnO (a-IGZO) thin film transistor (TFT) is used to clarify the phenomenon. Results from different top gate bias voltage confirms the bulk accumulation and better gate control.