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Title:
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Iron detection in crystalline silicon by carrier lifetime measurements for arbitrary injection and doping
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-2-2004
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ECN report number:
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Document type:
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ECN-RX--04-010
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Article (scientific)
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Number of pages:
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8
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Published in: Journal of Applied Physics (American Institute of Physics), , 2004, Vol.95, p.1021-1028.
Abstract:
An existing technique for accurate measurement of iron in silicon, whichwas previously restricted to low-injection and a narrow doping range,
has been extended to arbitrary injection and doping levels. This allows
contact-less lifetime measurement techniques to be used for very sensitive
and rapid iron detection under a wide range of conditions. In addition,
a new, easily measured and unambiguous ?fingerprint? of iron in silicon
is identified. It is based on the invariant nature of the excess carrier
density at which the injection-dependent lifetime curves, measured before
and after iron-boron pair dissociation, cross over. This characteristic
crossover point lies in the narrow range of 1.4 to 2.0x1014cm-3,
provided only that the boron concentration is below 5x1016cm-3.
To demonstrate the value of these new techniques, they have been applied
to photovoltaic-grade cast multicrystalline silicon wafers.
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