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The Density of States in a-Si:C:H Revealed by Electrophotography

Published online by Cambridge University Press:  01 January 1993

R.A.C.M.M. Van Swaaij ,
W.P.M. Willems ,
J. Bezemer ,
M.B. Von Der Linden  and
W.F. Van Der Weg
R.A.C.M.M. Van Swaaij
Affiliation:
Department of Atomic and Interface Physics, Debye Institute, Utrecht University, P. O. Box 80.000, NL-3508 TA Utrecht, The Netherlands
W.P.M. Willems
Affiliation:
Stork Colorproofing B.V., P. O. Box 80.000, NL-5830 AE Boxmeer, The Netherlands
J. Bezemer
Affiliation:
Department of Atomic and Interface Physics, Debye Institute, Utrecht University, P. O. Box 80.000, NL-3508 TA Utrecht, The Netherlands
M.B. Von Der Linden
Affiliation:
Department of Atomic and Interface Physics, Debye Institute, Utrecht University, P. O. Box 80.000, NL-3508 TA Utrecht, The Netherlands
W.F. Van Der Weg
Affiliation:
Department of Atomic and Interface Physics, Debye Institute, Utrecht University, P. O. Box 80.000, NL-3508 TA Utrecht, The Netherlands
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Abstract

Electrophotographic dark decay measurements have been used to determine the surface density of states (SDOS) of a-Si:C:H. Injection of trapped charge from these deep states into the conduction band governs the dark discharge of a photoconductor, provided bulk generation and bulk space charge are negligible. It is found that the SDOS profiles peak around 0.60 eV below the conduction band for materials with different carbon concentration. This observation implies that the energy position of these states is fixed with respect to the conduction band edge, even though the optical band gap of these materials increases with increasing carbon concentration. The nature of these states may be ascribed to D− states, whose density is strongly enhanced by filling D° states when the material is charged negatively. Furthermore, we observed that the SDOS around 0.60 eV below the conduction band edge is approximately the same for materials with up to 8 at.% carbon. From temperature dependent measurements a value of 2·108 s−1 was obtained for the attempt-to-escape frequency.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 297: Symposium A – Amorphous Silicon Technology - 1993 , 1993 , 693
Copyright
Copyright © Materials Research Society 1993

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References

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