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Investigations of Tail and Defect States in a-Si0.6Ge0.4:H Alloys by PDS and ESR - Implications for the Interaction of Weak and Dangling Bonds

Published online by Cambridge University Press:  15 February 2011

Tilo P. Drüsedau ,
Andreas N. Panckow  and
Bernd Schröder
Tilo P. Drüsedau
Affiliation:
Institut für Experimentelle Physik / Abt. Festkörperphysik der Otto-von-Guericke-Universität PF 4120, D - 39016 Magdeburg, Germany
Andreas N. Panckow
Affiliation:
Institut für Experimentelle Physik / Abt. Festkörperphysik der Otto-von-Guericke-Universität PF 4120, D - 39016 Magdeburg, Germany
Bernd Schröder
Affiliation:
Fachbereich Physik und Forschungsschwerpunkt Materialwissenschaften der Universität, Kaiserslautern, PF 3049, D - 67663 Kaiserslautern, Germany
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Abstract

Investigations on the gap state density were performed on a variety of samples of hydrogenated amorphous silicon germanium alloys (Ge fraction around 40 at%) containing different amounts of hydrogen. From subgap absorption measurements the values of the “integrated excess absorption” and the “defect absorption” were determined. Using a calibration constant, which is well established for the determination of the defect density from the integrated excess absorption of a-Si:H and a-Ge:H, it was found that the defect density is underestimated by nearly one order of magnitude. The underlying mechanisms for this discrepancy are discussed. The calibration constants for the present alloys are determined to 8.3×1016 eV−1 cnr2 and 1.7×1016 cm−2 for the excess and defect absorption, respectively. The defect density of the films was found to depend on the Urbach energy according to the law derived from Stutzmann's dangling bond - weak bond conversion model for a-Si:H. However, the model parameters - the density of states at the onset of the exponential tails N*=27×1020 eV−1 cm−3 and the position of the demarcation energy Edb-E*=0.1 eV are considerably smaller than in a-Si:H.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 377: Symposium A – Amorphous Silicon Technology 1995 , 1995 , 571
Copyright
Copyright © Materials Research Society 1995

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References

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