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On the Origin of the Urbach Rule and the Urbach Focus

Published online by Cambridge University Press:  17 June 2013

J. A. Guerra ,
L. Montañez ,
F. De Zela ,
A. Winnacker  and
R. Weingärtner
J. A. Guerra
Affiliation:
Pontifical Catholic University of Peru, Sciences Department, Physics Section, Av. Universitaria 1801, Lima 32, Peru. University of Erlangen-Nurnberg, Institute of Material Science 6, Martensstr. 7, 91058 Erlangen, Germany
L. Montañez
Affiliation:
Pontifical Catholic University of Peru, Sciences Department, Physics Section, Av. Universitaria 1801, Lima 32, Peru.
F. De Zela
Affiliation:
Pontifical Catholic University of Peru, Sciences Department, Physics Section, Av. Universitaria 1801, Lima 32, Peru.
A. Winnacker
Affiliation:
University of Erlangen-Nurnberg, Institute of Material Science 6, Martensstr. 7, 91058 Erlangen, Germany
R. Weingärtner
Affiliation:
Pontifical Catholic University of Peru, Sciences Department, Physics Section, Av. Universitaria 1801, Lima 32, Peru. University of Erlangen-Nurnberg, Institute of Material Science 6, Martensstr. 7, 91058 Erlangen, Germany
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Abstract

A simple derivation of sub-bandgap exponential tails and fundamental absorption equations ruling the optical absorption of amorphous semiconductors are presented following the frozen phonon model. We use the Kubo-Greenwood formula to describe the average transition rate for the optical absorption process. Asymptotic analysis leads to the commonly observed exponential tail as well as the Tauc expression for the fundamental absorption. We test our theoretical results with experimental absorption coefficients of amorphous Si:H, SiC:H, AlN and SiN. The validity of the Urbach focus concept is evaluated.

Keywords

optical propertiesamorphoussputtering
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1536: Symposium A – Film Silicon Science and Technology , 2013 , pp. 139 - 145
Copyright
Copyright © Materials Research Society 2013 

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References

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