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Real Time Spectroscopic Ellipsometry of Amorphous Silicon Grown at High Deposition Rates by Hot-Wire CVD

Published online by Cambridge University Press:  01 February 2011

Brent P. Nelson  and
Dean H. Levi
Brent P. Nelson
Affiliation:
National Center for Photovolatics, National Renewable Energy Laboratory Golden, CO 80401, USA
Dean H. Levi
Affiliation:
National Center for Photovolatics, National Renewable Energy Laboratory Golden, CO 80401, USA
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Abstract

We use real-time spectroscopic ellipsometry (RTSE) for in-situ characterization of the optical properties and surface roughness (Rs) of hydrogenated amorphous silicon (a-Si:H) grown by hot-wire chemical vapor deposition (HWCVD) with varying deposition rates (5 to 120 Å/s). Early time evolution of the Rs during growth is remarkably similar for all deposition rates. During the first few Ås of growth, there is a sharp increase in Rs as the a-Si:H nucleates in separate islands. This is followed by a reduction of Rs as these areas coalesce into a bulk film, which occurs at an average thickness of 100 Å. After coalescence the Rs rises to a stable value that is dependent upon growth conditions with a general tendency for the Rs to increase with growth rate. However, neither the Rs nor the material electronic properties are unique for a given deposition rate. Films grown under high silane flow and low pressure have a better photoresponse and a lower Rs than films grown at the same deposition rate but with low silane flow and high pressure. We observe a stronger correlation of film properties with Rs than with deposition rate; namely a monotonic decrease in photo-response, and increase in optical gap, with increasing Rs.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 715: Symposium A – Amorphous and Heterogeneous Silicon-Based Films-2002 , 2002 , A17.3
Copyright
Copyright © Materials Research Society 2002

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