Accounting for the Dependence of Coil Sensitivity on Sample Thickness and Lift-Off in Inductively Coupled Photoconductance Measurements
Date
2019
Authors
Black, Lachlan
Macdonald, Daniel
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Publisher
IEEE
Abstract
Inductively coupled photoconductance measurements
are widely used to characterize carrier recombination in
crystalline silicon. We show that, contrary to what is usually supposed,
the sensitivity of such measurements is significantly dependent
on sample thickness in the range of typical wafer thicknesses,
due to the attenuation of the magnetic field with distance from
the coil. Sample thickness, as well as any separation from the coil,
should, therefore, be taken into account in system calibration in
order to avoid systematic errors. We investigate the magnitude of
this effect both experimentally and via analytical and finite-element
modeling for a range of commercial photoconductance measurement
systems with varying coil geometry. Finite-element modeling
is used to identify the functional form of the attenuation in the
regime of interest, and simple formulae are derived which allow the
experimentalist to correct for sample thickness and lift-off. Close
agreement is found between modeled and experimental attenuation
behavior. Finite-element modeling is also used to evaluate the magnitude
of skin effects, which are found to have a minor influence on
the measured conductance for the most highly conductive samples,
and to determine the lateral spatial variation of the coil sensitivity,
which is important for lifetime imaging techniques where photoconductance
measurements are used for calibration.
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Keywords
Charge carrier density, charge carrier lifetime, conductivity measurement, eddy currents, measurement techniques, photoconductivity, photovoltaic cells, silicon.
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Source
IEEE Journal of Photovoltaics
Type
Journal article
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Restricted until
2037-01-31
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