Thin-film transistors threshold voltage

In this paper, hydrogenated amorphous silicon thin film transistors (a-Si H TFTs) fabricated on a metal foil substrate is reported for active matrix OLEDs (AMOLEDs) displays. The electrical properties of a-Si H TFTs fabricated on a metal foil substrate are introduced. To increase the stability of a-Si H TFTs fabricated at low temperature on a metal foil substrate, negative bias applied to metal foil substrate can also recover the shifted threshold voltage during idle time. A new cathode-contact structure employing a normal top-emitting OLED, which is suited to n-type a-Si H TFT backplane is proposed. 

Early work by Toshiba on the effect of a-Si TFT instability on AMLCD lifetime is reported in Ibaraki, N. et ah. Threshold voltage instability of a-Si H TFTs in kquid crystal displays, J. Non-Crystalline Solids, 115, 138, 1989. See also Chiang, C. et ah, AMLCD lifetime evaluation based on AC electrical instabikty of amorphous silicon thin-film transistors, Euro Display 96, 13. 

Under the hypotheses that no = N and rj ds, the threshold voltage is equal to the pinch-off voltage Vp = Vth, and all the terms in the second row of Eq. [3.2] can be neglected to obtain Eq. [3.3]. In this case, the field-effect fibrous transistor can be considered as a planar thin film FET. 

In a thin-film transistor, the threshold voltage Vth is the gate voltage leading to complete depletion of the layer. Analogously to the definition for the inversion transistor... 

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