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Physics of Solid-Phase Epitaxy of Hydrogenated Amorphous Silicon for Thin Film Si Photovoltaics

Published online by Cambridge University Press:  01 February 2011

Paul Stradins ,
Yanfa Yan ,
Robert Reedy ,
David L. Young ,
Charles W Teplin ,
Eugene Iwaniczko ,
Yueqin Xu ,
Kim Jones ,
Glenn Teeter  and
A. Harv Mahan
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Paul Stradins
Affiliation:
pauls_stradins@nrel.gov, National Renewable Energy Laboratory, Senior Scientist II, 1617 Cole Blvd., Golden, CO, United States
Yanfa Yan
Affiliation:
yanfa_yan@nrel.com, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Robert Reedy
Affiliation:
bob_reedy@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
David L. Young
Affiliation:
david_young@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Charles W Teplin
Affiliation:
chaz_teplin@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Eugene Iwaniczko
Affiliation:
eugene_iwaniczko@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Yueqin Xu
Affiliation:
yueqin_xu@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Kim Jones
Affiliation:
kim_jones@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Glenn Teeter
Affiliation:
glenn_teeter@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
A. Harv Mahan
Affiliation:
harv_mahan@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Howard M. Branz
Affiliation:
howard_branz@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
Qi Wang
Affiliation:
qi_wang@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO, 80401, United States
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Abstract

Solid state crystallization of hydrogenated amorphous silicon (a-Si:H) prepared by hot-wire CVD is studied in solid phase epitaxy mode. By using a novel optical method combined with cross-sectional TEM and SIMS, a reduction of epitaxial growth speed is observed with increase in a-Si:H film thickness. Namely, in films thinner that 0.5 micron, solid phase epitaxy velocity depends linearly on film thickness. As the film thickness increases beyond 1 micron, the average velocity of solid phase epitaxy decreases considerably with respect to that in thinner films. In this regime, its velocity becomes also time-dependent: initial slow propagation of crystallization front gets considerably accelerated after the front has traveled above 400nm. SIMS thickness profiles of hydrogen shows considerably more residual hydrogen in thicker films after the start of solid phase epitaxy. In addition, prolonged pre-dehydrogenation at lower temperatures results in the increase in the average epitaxy speed in thicker films. These phenomena are likely related to delayed hydrogen outdiffusion in thicker films, which also leads to time-dependent speed of the solid-phase epitaxy front. We conclude that excess residual hydrogen reduces the rate of solid-phase crystalline growth.

Keywords

amorphousSiepitaxy
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 910: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology – 2006 , 2006 , 0910-A15-05
Copyright
Copyright © Materials Research Society 2006

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