Abnormal Subthreshold Swing Decrease in a-InGaZnO Thin-Film Transistor After Self-Heating Stress

This study investigates abnormal decreased subthreshold swing (S.S.) and increased ${I}_{ \mathrm{\scriptscriptstyle ON}}$ in back-channel etch (BCE) InGaZnO (IGZO) thin-film transistors (TFTs) under self-heating stress (SHS) operation. With confirmation of the energy band diagram via gate-to-source ( ${C}_{\text {GS}}$ ) and gate-to-drain capacitance ( ${C}_{\text {GD}}$ ) measurements of the capacitance–voltage ( ${C}$ – ${V}$ ) curve, the degradation mechanism is further inferred. The degradation arises from uneven trapped charges by the thermal field. To illustrate the mechanism, the device with uneven trapped charges and the double-gate device with different values of ${V}_{\text {TH}}$ are simulated by SILVACO-TCAD.