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Transient Photocurrents in Microcrystalline Silicon Films

Published online by Cambridge University Press:  01 February 2011

Steve Reynolds
Affiliation:
School of Science and Engineering, University of Abertay Dundee, Bell Street, Dundee U.K.
Vladimir Smirnov
Affiliation:
School of Science and Engineering, University of Abertay Dundee, Bell Street, Dundee U.K.
Charlie Main
Affiliation:
School of Science and Engineering, University of Abertay Dundee, Bell Street, Dundee U.K.
Reinhard Carius
Affiliation:
Forschungszentrum Jülich, Institute for Photovoltaics, D-52425 Jülich, Germany.
Friedhelm Finger
Affiliation:
Forschungszentrum Jülich, Institute for Photovoltaics, D-52425 Jülich, Germany.
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Abstract

Transient photoconductivity in microcrystalline silicon thin films prepared by VHF PECVD over a range of [silane]: [silane + hydrogen] concentrations γ from 3 to 6.3% has been measured as a function of temperature (210 K - 390 K) and laser pulse density (1013 – 1016 cm3). The behavior of highly crystalline films (γ ∼ 3%) bears certain similarities to n-type amorphous silicon, where the power law decay at long times is controlled by hole rather than electron kinetics. As γ approaches 6% the decay begins to resemble that of intrinsic amorphous silicon, consistent with structural studies which indicate a transition from crystalline to amorphous character. Transient photocurrent density of states spectroscopy on transitional films suggests a similar deep defect density to high-quality amorphous silicon, but a larger conduction band tail energy of some 30 meV and a tenfold increase in localised state density at a depth of about 0.4 eV.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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