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A New Technique for Determining Midgap States and Hole Localization in a-Si:H Devices

Published online by Cambridge University Press:  25 February 2011

Vikarm L. Dalal  and
Ralph D. Knox
Vikarm L. Dalal
Affiliation:
Department of Electrical Engineering and Computer Engineering, Iowa State University Ames, IA 50011
Ralph D. Knox
Affiliation:
Microelectronics Research Center, Iowa State University Ames, IA 50011
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Abstract

We describe a technique for measuring localization of holes in mid-gap states in high quality a-Si:H devices. The localization of holes is determined by measuring quantum efficiency of a-Si:H devices as a function of reverse bias voltage and wavelength of light. It is shown that the QE of localized holes increases significantly upon application of high electric fields, whereas the QE of de-localized holes does not show such a behavior. The voltage-induced increase in QE is explained using a Frenkel-Poole tunneling model. It is also shown that the density of mid-gap states (states in which holes are localized) increases significantly upon light soaking, and that a major consequence of this increase in mid-gap density is a decrease in the electric field in the device. The decrease in electric field is experimentally estimated by fitting the increased current due to tunneling to the expression for Frenkel-Poole tunneling.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 192: Symposium O – Amorphous Silicon Technology - 1990 , 1990 , 713
Copyright
Copyright © Materials Research Society 1990

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References

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