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The Effect of Oxygen Contamination on the Electronic Properties of Hot-Wire CVD Amorphous Silicon Germanium Alloys

Published online by Cambridge University Press:  01 February 2011

Shouvik Datta ,
J. David Cohen ,
Steve L. Golledge ,
Yueqin Xu ,
A. H. Mahan ,
James R. Doyle  and
Howard M. Branz
J. David Cohen
Affiliation:
[email protected], University of Oregon, Department of Physics, Department of Physics, University of Oregon, Eugene, OR, 97403, United States
Steve L. Golledge
Affiliation:
[email protected], University of Oregon, Surface Analytical Facility,CAMCOR, Eugene, OR, 97403, United States
Yueqin Xu
Affiliation:
[email protected], National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO, 80401, United States
A. H. Mahan
Affiliation:
[email protected], National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO, 80401, United States
James R. Doyle
Affiliation:
[email protected], National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO, 80401, United States
Howard M. Branz
Affiliation:
[email protected], National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO, 80401, United States
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Abstract

A series of four a Si,Ge:H alloy samples with Ge fractions near 30 at.% were deposited by hot-wire CVD (HWCVD) using a Ta filament maintained at 1800oC. During film growth, the level of oxygen contamination was varied from less than 1019 cm−3 to roughly 5 × 1020 cm−3 using a controlled air-leak. The electronic properties of these films were then characterized using transient photocapacitance (TPC) and transient photocurrent (TPI) spectroscopy, as well as the drive-level capacitance profiling (DLCP) techniques. We observed an unexpected systematic improvement of the electronic properties of these HWCVD a Si,Ge:H with increasing oxygen impurity level, which was reflected by a decrease in the deduced Urbach energies. Comparing these with films co-deposited on stainless-steel versus p+ c-Si substrates, we found significantly better electronic properties in the latter case. Comparisons of the TPC and TPI spectra indicated a very high level of hole collection, consistent with these narrow bandtail distributions.

Keywords

amorphouselectronic structureoptical properties
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-A02-05
Copyright
Copyright © Materials Research Society 2006

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