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Transient Decay from the Steady-State in Microcrystalline Silicon

Published online by Cambridge University Press:  01 February 2011

R. Brüggemann
Affiliation:
Fachbereich Physik, Carl von Ossietzky Universität Oldenburg, 26111 Oldenburg, Germany
S. Reynolds
Affiliation:
Fachbereich Physik, Carl von Ossietzky Universität Oldenburg, 26111 Oldenburg, Germany
C. Main
Affiliation:
School of Science and Engineering, University of Abertay Dundee, Dundee DD1 1HG, Scotland, United Kingdom
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Abstract

We measured the transient photocurrent decay from the steady state in microcrystalline silicon from plasma-enhanced chemical vapor deposition and hot-wire chemical vapour deposition. Samples exhibiting a range of photoconductive properties in terms of both the majority and minority carrier mobility-lifetime products or sub-gap absorption coefficients were studied. Measurements were made over a wide range of steady-state photogeneration rates for which we detail the variation with generation rate of the decay time. Samples with a short steady-state photocarrier lifetime show a long decay time. We relate the slow decay process to the much larger density of traps in the band gap in the poor-quality samples. Trapped carriers are released, undergo emission and trapping processes and eventually recombine in these samples, on a much longer time-scale than in the higher-quality samples so that the decay time cannot be taken as a fingerprint for photo-electronic quality. Analytical and numerical modeling indicate bimolecular recombination behavior during the decay. Results are in agreement with free-carrier interaction with exponentially distributed band-tail states.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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