Hysteresis phenomenon of hydrogenated amorphous silicon thin film transistors for an active matrix organic light emitting diode

Abstract We have investigated an origin of hysteresis of hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) and analyzed an effect of hysteresis when a-Si:H TFT is a pixel element of active matrix organic light emitting diode (AMOLED). When a-Si:H TFT is placed under different starting gate-voltages, such as 10 and 5 V, the measured transfer characteristics with 1 μA at VDS = 10 V shows that the gate-voltage shift of 0.15 V occurs due to the different quantities of trapped charge. When the step gate-voltage in the transfer curve is decreased from 0.5 to 0.05 V, the gate-voltage shift is decreased from 0.78 to 0.39 V due to the change of charge de-trapping rate. The measured OLED current in the widely used 2-TFT pixel shows that the gate-voltage of TFT in the previous frame can influence OLED current in the present frame by ±35% due to the change of interface trap density induced by different starting gate-voltages.