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Illumination instabilities in ZnO/HfO2 thin-film transistors and influence of grain boundary charge

Published online by Cambridge University Press:  07 June 2012

Jeffrey J. Siddiqui*
Affiliation:
Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109
Jamie D. Phillips
Affiliation:
Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109
Kevin Leedy
Affiliation:
Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433
Burhan Bayraktaroglu
Affiliation:
Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

The illumination instabilities of nanocrystalline ZnO thin-film transistors (TFT) with HfO2 gate dielectrics are reported via zero gate bias multiwave length illumination stress method. TFT IDVG curves exhibit a negative threshold voltage shift together with an increase in ID off current and increase in subthreshold slope with increasing photon energy and illumination time. Analysis of transistor characteristics indicates that one component governing negative threshold voltage shifts is a decrease in grain boundary-trapped charge areal density due to illumination. This relationship can be explained by conduction based on thermionic emission over potential barriers formed at the ZnO crystallite boundaries. ID off-state current trends with photon energy in a manner consistent with exponentially decreasing absorption below the conduction band edge.

Type
Reviews
Copyright
Copyright © Materials Research Society 2012

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References

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