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States in the Gap of Improved a-Ge:H Studied by Photomodulation Spectroscopy

Published online by Cambridge University Press:  21 February 2011

L. Chen ,
J. Tauc ,
D. Pang ,
W. A. Turner  and
W. Paul
L. Chen
Affiliation:
Division of Engineering and Department of Physics, Brown University, Providence, RI02912
J. Tauc
Affiliation:
Division of Engineering and Department of Physics, Brown University, Providence, RI02912
D. Pang
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
W. A. Turner
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
W. Paul
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
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Abstract

The photomodulation spectra of a-Ge:H of average photoelectronic quality(ημπ = 1 × 10-10cm2/V) and of improved quality (ημπ = 3 × 10-7cm2/V), produced under different plasma conditions in an r.f. diode reactor by glow discharge, were measured at 80K and are analyzed in analogy with earlier studies of a-Si:H. The spectra of the poorer material are dominated by transitions between dangling bond states and the conduction and valence bands. By contrast, the spectra of the better material require contributions of transitions from the band tail states, indicating that the reduced defect density has resulted in pump-beam induced quasi-Fermi levels reaching near the conduction and valence band edges. A very acceptable fit between plausible density-of-states distributions and the experimental spectra has been found.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 219: Symposium A – Amorphous Silicon Technology - 1991 , 1991 , 575
Copyright
Copyright © Materials Research Society 1991

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References

REFERENCES

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