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

Abstract

Threshold voltage shift ( $\Delta V_{\mathrm{ TH}}$ ) effect of hydrogenated amorphous silicon thin-film transistors under bipolar pulse bias stress (BPBS) is investigated. The dependence of the $\Delta V_{\mathrm{ TH}}$ 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 $\Delta V_{\mathrm{ TH}}$ , 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 $\Delta V_{\mathrm{ TH}}$ , especially when the thin-film transistors work relatively at high temperature.