Transient Behavior of the ${hbox{a}}{hbox{-}}{hbox{Si}}:{hbox{H/Si}}_{3}{hbox{N}}_{4}$ MIS Capacitor and Its Impact on Image Quality of AMLCDs Addressed by a-Si:H Thin-Film Transistors |
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Authors: | Genshiro Kawachi Masahiro Ishii Nobutake Konishi |
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Affiliation: | Hitachi Displays, Chiba; |
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Abstract: | Transient behavior of the a-Si:H/Si3N4 metal-insulator-semiconductor (MIS) capacitor and its relationship to the performance of a-Si:H based active-matrix liquid crystal displays (AMLCDs) have been analyzed in detail. A relatively slow voltage decay whose time constant is comparable to the frame period of the LCD is observed after applying a voltage pulse that drives the MIS capacitor into the electron accumulation. The voltage decay is due to electron emission from the localized states at the a-Si:H/Si3N4 interface. It is also found that this voltage transient results in a shift in the optimum common voltage for the liquid crystal pixel by changing the temperature and light exposure when an MIS-type capacitor is inserted between the pixel electrode and the adjacent gate bus-line as the storage capacitor. This shift in the optimum common voltage affects the image quality of AMLCDs through image sticking or flicker. A similar effect can occur even without an MIS-type storage capacitor in high resolution AMLCDs, where the gate-source parasitic capacitance of the thin-film transistor is comparable to the net capacitance of the pixel. It is important to take such transient effects of MIS capacitors into consideration in pixel designing |
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