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The Origin of the Enhanced Optical Absorption in Hot Wire Microcrystalline Silicon

Published online by Cambridge University Press:  10 February 2011

F. Diehl ,
B. Schröder  and
H. Oechsner
F. Diehl
Affiliation:
Department of Physics and Center of Materials Research, University of Kaiserslautern, D-67653 Kaiserslautem, Germany
B. Schröder
Affiliation:
Department of Physics and Center of Materials Research, University of Kaiserslautern, D-67653 Kaiserslautem, Germany
H. Oechsner
Affiliation:
Department of Physics and Center of Materials Research, University of Kaiserslautern, D-67653 Kaiserslautem, Germany
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Abstract

The phenomenon of enhanced optical absorption in hot wire microcrystalline silicon (hw-μ-Si:H) has been investigated with respect to the structural properties of the as deposited as well as annealed films. The influence of the structural properties on the absorption behavior is explained within the framework of a model. In this model the μc-Si:H is assumed to consist of crystalline grains surrounded by grain boundaries embedded into an amorphous matrix. Because of the relaxation of the k-selection rule the absorption is supposed to be higher for the disordered grain boundaries than for the crystalline grains. The absorption coefficient α is derived from the superposition of the absorption coefficients for the amorphous, crystalline and grain boundary regions weighted by their appropriate volume fractions. According to experimental results it is furthermore assumed that the absorption of the grain boundary regions correlates with the hydrogen content of the films. The model is proven and confirmed by crucial experiments especially concerning the influence of the hydrogen content on the absorption coefficient. Other possible reasons that might influence the enhanced optical absorption such as strain induced changes of α and light scattering effects are also discussed and explicitely excluded by appropriate experiments to be the essential enhancement reasons.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 507: Symposium A – Amorphous & Microcrystalline Silicon Technology 1998 , 1998 , 819
Copyright
Copyright © Materials Research Society 1998

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References

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