Drain-Bias Dependence of Threshold Voltage Stability of Amorphous Silicon TFTs

Effect of channel length on the threshold voltage degradation of hydrogenated amorphous silicon TFTs due to the drain bias stress

“…Smaller V T shift in the short channel TFTs can be explained by the concentration of the channel charge varying with the drain bias. As the drain bias increases, the carrier concentration in the channel decreases [1]. Since the portion of the depleted charges over total charges increases with reducing channel length, the short channel TFTs have the smaller carrier concentration than the long channel TFTs.…”

Amorphous Silicon Transistors and Photodiodes

“…The V T shift is smaller in saturation [17] primarily because the channel charge is lower, and it is the channel charge that determines the V T shift.…”

Transparent OLED Displays

“…In this case, long term stability plays a critical role for analog devices because a shift of threshold voltage (V th ) concomitantly leads to a change of the individual pixel brightness. There have been many investigations of bias-induced instabilities in a-Si:H [64][65][66], where a shift of V th of the order of several volts after a few hours of bias stress is quite common. Only recently the question of operational stability under stress has been tackled for some oxide based TFT structures like ZTO [67,68] and a-IGZO [69,70].…”