Degradation Evaluation of α-IGZO TFTs for Application to AM-OLEDs

We have evaluated the characteristic degradation of amorphous-InGaZnO4thin-film transistors (α-IGZO TFTs) to apply to active-matrix organic light-emitting diode displays (AM-OLEDs) using current-voltage (I-V) and capacitance-voltage (C-V) curves and an extraction technique of trap densities. First, the degradation was a parallel shift of the I-V andC-Vcurves after a short time, mainly caused by fixed charge injection into the gate insulator when gate voltage stress was applied by supposing switching TFTs in AM-OLEDs. Second, the degradation was a parallel shift of the I -V curve and slope dullness of the C-V curve after a long time, mainly caused by trap generation in the channel layer when drain current stress was applied by supposing driving TFTs in AM-OLEDs. We should note that two different degradation modes occur when α-IGZO TFTs are applied to AM-OLEDs.