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Relationship between Phase Shift, Square-Wave Response and Density of States in Modulated Photocurrent Spectroscopy

Published online by Cambridge University Press:  01 February 2011

Steve Reynolds  and
Charlie Main
Steve Reynolds
Affiliation:
[email protected], Forschungszentrum Juelich, Institute of Photovoltaics, Leo Brandt Str., Juelich, NRW, D-52425, Germany, +44 2461 612609, +44 2461 613735
Charlie Main
Affiliation:
[email protected], University of Dundee, Division of Electronic Engineering and Physics, Nethergate, Dundee, Angus, DD1 4HN, United Kingdom
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Abstract

Low- and high-frequency modulated photoconductivity measurements (LF and HF MPC) have been made on amorphous silicon films prepared by the expanding thermal plasma (ETP) and RF PECVD techniques. Time constants have been measured by decay of square wave excitation and behavior of complex frequency response. The influence of quasi-Fermi level position has been examined. Band tail slopes of 32 meV (ETP) and 37 meV (PECVD), and defect densities of order 1018 and 1017 cm-3 eV-1 respectively are found. Tail state capture coefficients of order 3×10-8 cm3 s-1 are calculated from overlapping LF and HF regimes. Defect state values for ETP (< 10-8 cm3 s-1) are smaller than for PECVD silicon films (> 10-7 cm-3 s-1).

Keywords

photoconductivitydefectselectronic material
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 910: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology – 2006 , 2006 , 0910-A09-01
Copyright
Copyright © Materials Research Society 2006

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References

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