Threshold Voltage Shift Effect of a-Si:H TFTs Under Bipolar Pulse Bias

Threshold voltage shift (Delta V-TH) effect of hydrogenated amorphous silicon thin-film transistors under bipolar pulse bias stress (BPBS) is investigated. The dependence of the Delta V-TH effect on the signal pulsewidth, stress temperature, and negative pulse voltage magnitude of the BPBS is systematically measured, and explained by the charge trapping and detrapping theory. Results show that the BPBS leads to a noticeably suppressed Delta V-TH, compared with the conventional unipolar pulse bias stress. It is suggested that the BPBS with proper negative pulse voltage magnitude and low pulse frequency is an effective way of suppressing Delta V-TH, especially when the thin-film transistors work relatively at high temperature.