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Physics of Below Threshold Current Distribution in a-Si:H TFTs

Published online by Cambridge University Press:  10 February 2011

M. S. Shur
Affiliation:
University of Virginia, Thornton Hall, Charlottesville, VA 22903-2442, U.S.A.
S. C. Deane
Affiliation:
Philips Research Laboratory, Redhill, Surrey, RH1 5HA, U.K.
M. Hack
Affiliation:
dpiX, 3406 Hillview Ave., Palo Alto, CA 94304-1345, U.S.A.
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Abstract

We have examined the material properties and operation of bottom-gate amorphous silicon thin film transistors (TFTs) using temperature measurements of the subthreshold current. From the derivative of current activation energy with respect to gate bias, we have deduced information about the density of states for several different transistor types. We have demonstrated that, in TFTs with thin active layers and top nitride passivation, the current conduction channel moves from the gate insulator interface to the passivation insulator interface as the transistor switches off. Our 2D simulations clarify these experimental results. We have examined the effect of bias stress on the transistors and analyzed the resulting reduction in the subthreshold slope. Based on these results, we have extended our analytic amorphous silicon TFI SPICE model to include the effect of bias stress.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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