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Density of States of Amorphous Germanium Thin Films Deposited by the Pecvd of H2-Diluted Germane

Published online by Cambridge University Press:  25 February 2011

C. Godet ,
V. Chu ,
B. Equer ,
Y. Bouizem ,
L. Chahed ,
I. El Zawawi ,
M. L. Theye ,
S. Basrour ,
J. C. Bruyere  and
J.P. Stoquert
C. Godet
Affiliation:
Laboratoire de Physique des Interfaces et des Couches Minces, UPR A 0258 - CNRS, Ecole Polytechnique - 91128 Palaiseau-Cedex, (France).
V. Chu
Affiliation:
Laboratoire de Physique des Interfaces et des Couches Minces, UPR A 0258 - CNRS, Ecole Polytechnique - 91128 Palaiseau-Cedex, (France).
B. Equer
Affiliation:
Laboratoire de Physique des Interfaces et des Couches Minces, UPR A 0258 - CNRS, Ecole Polytechnique - 91128 Palaiseau-Cedex, (France).
Y. Bouizem
Affiliation:
Laboratoire d’Optique des Solides, URA CNRS 781, Université P. et M. Curie, 4 place Jussieu, 75252 Paris-Cedex 05, (France).
L. Chahed
Affiliation:
Laboratoire d’Optique des Solides, URA CNRS 781, Université P. et M. Curie, 4 place Jussieu, 75252 Paris-Cedex 05, (France).
I. El Zawawi
Affiliation:
Laboratoire d’Optique des Solides, URA CNRS 781, Université P. et M. Curie, 4 place Jussieu, 75252 Paris-Cedex 05, (France).
M. L. Theye
Affiliation:
Laboratoire d’Optique des Solides, URA CNRS 781, Université P. et M. Curie, 4 place Jussieu, 75252 Paris-Cedex 05, (France).
S. Basrour
Affiliation:
Laboratoire d’Etude des Propriétés Electroniques des Solides, CNRS, , BP 166X, 38042 Grenoble-Cedex, (France).
J. C. Bruyere
Affiliation:
Laboratoire d’Etude des Propriétés Electroniques des Solides, CNRS, , BP 166X, 38042 Grenoble-Cedex, (France).
J.P. Stoquert
Affiliation:
Laboratoire PHASE, Centre de Recherches Nucleaires, BP 20, 67037 Strasbourg, (France).
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Abstract

The disorder in a-Ge:H thin films produced by the plasma-enhanced chemical vapor deposition (PECVD) technique is strongly reduced when the GeH4 gas is diluted at 1% in H2 and the radiofrequency power density is increased to 0.1 W.cm−2. This improvement is attributed to a better surface passivation by the hydrogen atoms during the growth. However, the poor transport properties indicate a still high defect density. The midgap defect absorption and the Urbach energy, obtained from the photothermal deflection spectra calibrated with optical data, both decrease as a function of the film thickness. The optical defect density is calibrated with EPR spin measurements. For a-Ge:H films thicker than 2 μm, obtained at a deposition temperature Ts ranging from 150 to 250°C, the Urbach tail parameter E° is lower than 50 meV and not sensitive to Ts ; the dangling bond density is around 4.107 cm−3, which is higher by a factor of 100 than in a-Si:H. Preliminary transport measurements indicate that the Fermi level density of states is larger than 1018 cm−3.eV−1.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 192: Symposium O – Amorphous Silicon Technology - 1990 , 1990 , 163
Copyright
Copyright © Materials Research Society 1990

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References

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