Stable a-Si:H circuits based on short-term stress stability of amorphous silicon thin film transistors

Hydrogenated amorphous silicon (a-Si:H) technology is interesting for large-area active matrix structure due to its good uniformity over large-area, low-temperature, and low-cost fabrication, and its industrial accessibility. However, the circuits implemented in this technology suffer from the instability of the material under prolonged bias stress. To improve the circuit stability, we present a circuit design technique based on the stability of a-Si:H thin film transistors (TFTs) under short-term bias stress. Here, an a-Si:H local current source (LCS) is used to adjust the circuit current bias. Since the LCS circuit is under stress for a small fraction of operation time, its current remains stable. The measurement and analysis of the LCS circuit indicate that the a-Si:H TFT is stable under short-term bias stress for over 50000h. Also, we present a pixel circuit based on this technique for active matrix organic light emitting diode displays.