Long Life-Time Amorphous-InGaZnO TFT-Based Shift Register Using a Reset Clock Signal

We report a long life-time shift register (SR) made of amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The life-time of an SR is determined by the stability of the pull-down TFT, which is always under positive bias stress (PBS). To compensate for the nonrecovering characteristic of a-IGZO TFTs, the gate ON time of the pull-down TFT is reduced from 50% to 5% duty ratio by introducing a reset clock signal. By fitting the TFT's PBS-induced threshold voltage shifts to stretched exponentials, the life-time of the SR is estimated to increase from 1.7 to 17.5 years, owing to the reset clock signal with short-term duty.