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The Density of States in Undoped and Doped Amorphous Silicon-Germanium Alloys Determined through Photoyield Spectroscopy

Published online by Cambridge University Press:  25 February 2011

S. Aljishi
Affiliation:
Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80, F.R.G.
Jin Shu
Affiliation:
Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80, F.R.G.
L. Ley
Affiliation:
Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80, F.R.G.
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Abstract

Photoelectron yield spectroscopy is used to study the occupied density of states (DOS) in undoped and doped a-Si, Ge:H alloys. We find a shift in the top of the valence band to lower energy as the Ge content is increased. The width of the defect band becomes abruptly narrower when Ge is initially introduced. This change is accompanied by a significant shift in the relative position of the Fermi level towards midgap. The defect peak tracks the valence band throughout the entire composition range. The intrinsic valence band tail in the alloys is found to be an exponential with a characteristic slope of 50 to 60 meV independent of composition. Boron and phosphorous doping affect the DOS of the alloys in a manner similar to that measured in a-Si:H.

Type
Research Article
Copyright
Copyright © Materials Research Society 1989

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References

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