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Thermal Equilibration Between Band Tail and Near Surface Defect States in Hydrogenated Amorphous Silicon and Silicon-Germanium Alloys

Published online by Cambridge University Press:  25 February 2011

Samer Aljishi ,
Shu Jin ,
Lothar Ley  and
Sigurd Wagner
Samer Aljishi
Affiliation:
Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-7000 Stuttgart 80, Federal Republic of, Germany.
Shu Jin
Affiliation:
Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-7000 Stuttgart 80, Federal Republic of, Germany.
Lothar Ley
Affiliation:
Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-7000 Stuttgart 80, Federal Republic of, Germany.
Sigurd Wagner
Affiliation:
Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, U.S.A.
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Abstract

We employ total yield photoelectron spectroscopy to measure the density of occupied states at the clean a-SixGe1_x:H alloy surface. The near surface defect states are observed to lie at 0.57 eV above the valence band edge with a density of 4×l017 cm−3, independent of Ge content. The valence band tail characteristic energy is also measured to be independent of alloy composition with an average value of 54 meV. We demonstrate that thermodynamic equilibrium at the surface between weak bonds (forming the valence band tail) and the dangling bonds provides an excellent description of the experimental data and explains why the surface state density in a-Si:H cannot be lowered below the 1011 to 1012 cm−2 range.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 192: Symposium O – Amorphous Silicon Technology - 1990 , 1990 , 195
Copyright
Copyright © Materials Research Society 1990

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References

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