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Analysis of the Physical Origin of the blue shift of the Optical Bandgap of a-Si:H based Multilayers

Published online by Cambridge University Press:  16 February 2011

Norbert Bernhard  and
Gottfried H. Bauer
Norbert Bernhard
Affiliation:
Institut für Physikalische Elektronik, Universität Stuttgart, Pfaffenwaldring 47, D-70569 Stuttgart, Germany
Gottfried H. Bauer
Affiliation:
Institut für Physikalische Elektronik, Universität Stuttgart, Pfaffenwaldring 47, D-70569 Stuttgart, Germany
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Abstract

The physical origin of the blue shift of the optical Taue bandgap of compositional multilayers of a-Si:H and its alloys with Ge, C or N is analysed. It is shown that for multilayers with bandgap differences up to 0.7 eV between well and barrier Material, the effect can be understood completely classical in terms of the effective medium approximation, when the mean composition of the multilayer films is not kept constant. For the variation of both the electronic well and barrier widths a shift of the Taue bandgap is theoretically expected. It is of the same order of magnitude as the effect which is experimentally observed. Interfacial transition layers can account for a blue shift also for higher bandgap differences, as usually the case in a-Si:H/a-SiNx:H Multilayers, and when the mean composition of the multilayers is kept constant.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 336: Symposium A – Amorphous Silicon Technology - 1994 , 1994 , 401
Copyright
Copyright © Materials Research Society 1994

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References

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