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Electronic Properties of ZnO Varistors: A New Model*

Published online by Cambridge University Press:  15 February 2011

G. E. Pike
G. E. Pike*
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico, 87185
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Abstract

Much of the research on ZnO varistors has concentrated on the explanation of their dc current-voltage characteristics. However, varistors also have unusual ac properties which can be technologically important, and must be described by any comprehensive model. In an ideal varistor with identical grain boundaries throughout, there should be no dispersive capacitance at zero bias. In real varistors this capacitance varies considerably with frequency. This dispersion has two causes, charge trapping in the depletion regions and differing grain boundary barriers. Calculations for each process are given. For voltages well below the varistor breakdown value, the low frequency capacitance increases with applied voltage. At even higher voltages the capacitance turns over and becomes negative. All of these effects can be described with a double depletion layer/thermionic emission model. The anomalous capacitance behavior with bias is due to the modulation of the potential barriers by charge trapping at the grain boundaries. In the varistor breakdown regime minority carriers created by impact ionization are important.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 5: Symposium B – Grain Boundaries in Semiconductors , 1981 , 369
Copyright
Copyright © Materials Research Society 1982

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Footnotes

*

This work performed at Sandia National Laboratories, supported by the U. S. Department of Energy under contract DE–AC04–76–DP00789.

References

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