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Low Filament Temperature Deposition of a-Si:H by Catalytic Chemical Vapor Deposition

Published online by Cambridge University Press:  01 January 1993

P. Brogueira ,
S. Grebner ,
F. Wang ,
R. schwarz ,
V. Chu  and
J.P. Conde
P. Brogueira
Affiliation:
Instituto Superior Técnico, Department of Physics, 1096 Lisboa Codex,Portugal
S. Grebner
Affiliation:
Physics Department - E-16, Technical University of Munich, D-8046 Garching, Germany
F. Wang
Affiliation:
Physics Department - E-16, Technical University of Munich, D-8046 Garching, Germany
R. schwarz
Affiliation:
Physics Department - E-16, Technical University of Munich, D-8046 Garching, Germany
V. Chu
Affiliation:
INESC, Rua Alves Redol 9, 1000 Lisboa, Portugal
J.P. Conde
Affiliation:
Instituto Superior Técnico, Department of Physics, 1096 Lisboa Codex,Portugal
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Abstract

Hydrogenated amorphous silicon, a-Si:H, is deposited from silane (SiH4 ) and hydrogen (H2 ) using a tungsten wire at low filament temperatures (Tfil = 1200°C) by catalytic chemical vapor deposition.

The deposition rate increases monotonically with the depositions pressures and shows a maximum at an H2 : SiH4 flow ratio of unity. Vanishingly small deposition rates were observed for silane-only depositions and for H2 -to-SiH4 flow ratios of 2.5 and above. The optoelectronic properties show complex dependence on substrate temperature (Tsub ). Three intervals of Tsub with distinct optoelectronic were observed: as Tsub increases from 180 to 220°C, the optical bandgap, EgTauc increases from 1.9 to 2.4eV, the dark conductivity,σd, decreases from 10-10 to 10-15 Ω-1 cm -1and the photoconductivity, σph , decreases from 10-5 to 10-10Ω-1 cm -1 (region (i)). As Tsub increases from 220 to 250 °C, EgTauc decreases to 1.8eV and the photosensitivity, σph/σd decreases to ~ 1 due to an increase of both σd and σph (region (ii)). Throughout these two regions, the photoconductivity γ factor remains between 0.6 and 0.9 and the activation energy of the dark conductivity, Ea,σd , remains between 0.7 and 0.9eV. Above 250°C, the σph and σd remain approximately constant at 10-4 Ω-1 cm -1 and γ decreases to below 0.5 and Ea,σd ~ 0.3eV.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 297: Symposium A – Amorphous Silicon Technology - 1993 , 1993 , 121
Copyright
Copyright © Materials Research Society 1993

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References

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