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Purely Intrinsic Poly-Silicon Films by Hot Wire Chemical Vapor Deposition

Published online by Cambridge University Press:  15 February 2011

J. K. Rath ,
K. F. Feenstra ,
D. Ruff ,
H. Meiling  and
R. E. I. Schropp
J. K. Rath
Affiliation:
Utrecht University, Debye Institute, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
K. F. Feenstra
Affiliation:
Utrecht University, Debye Institute, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
D. Ruff
Affiliation:
Philipps-Universitat Marburg, D-35032 Marburg, Germany.
H. Meiling
Affiliation:
Utrecht University, Debye Institute, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
R. E. I. Schropp
Affiliation:
Utrecht University, Debye Institute, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
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Abstract

Poly-silicon films have been prepared by hot-wire chemical vapor deposition (HWCVD) from hydrogen diluted silane gas at a low temperature (430 °C). The optical gap of the poly-silicon films is 1.1 eV, though with a higher optical absorption than c-Si. The grains have a preferential orientation (220) perpendicular to the substrate with an average crystallite size of 70 nm. The crystalline volume fraction is 95% with complete coalescence of grains. Large structures up to 0.5 μm could be observed in the AFM micrograph. The activation energy (0.54 eV) and the low carrier concentration (1011 cm−3) indicate a fully intrinsic nature of the films. The μτ product of carriers is 7.1×10−7 cm2V−1 whereas the ambipolar diffusion length (LD) is 334 nm. The excellent photo-conductive properties are attributed to the low (∼1017 cm−3) defect density. The HWCVD poly-silicon films showed a very small temperature dependence of mobility, indicating negligible trapping of carriers at the grain boundaries. Preliminary n-i-p cells incorporating poly-silicon i-layer yielded 3.15 % efficiency.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 452 , 1996 , 977
Copyright
Copyright © Materials Research Society 1997

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References

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