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Electronic Transitions in Mixed Phase Crystalline/Amorphous Silicon in the Low Crystalline Fraction Regime

Published online by Cambridge University Press:  15 February 2011

J. David Cohen
Affiliation:
Department of Physics, University of Oregon, Eugene, OR 97403
Daewon Kwon
Affiliation:
Department of Physics, University of Oregon, Eugene, OR 97403
Chih-Chiang Chen
Affiliation:
Department of Physics, University of Oregon, Eugene, OR 97403
Hyun-Chul Jin
Affiliation:
Department of Physics, University of Oregon, Eugene, OR 97403
Eric Hollar
Affiliation:
Coordinated Science Laboratory and Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801
Ian Robertson
Affiliation:
Coordinated Science Laboratory and Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801
John R. Abelson
Affiliation:
Coordinated Science Laboratory and Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801
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Abstract

Amorphous silicon films were prepared by dc reactive magnetron sputtering under conditions approaching the phase transition to microcrystallinity. Using TEM imaging these films were found to contain clusters of 5 to 50 nm sized Si crystallites embedded in an amorphous silicon matrix. Photocapacitance and transient photocurrent sub-band-gap optical spectra of this material appear to consist of a superposition of a spectrum typical of amorphous silicon together with an optical transition, with a threshold near 1. 1eV, that exhibits a very large optical cross section. This transition arises from valence band electrons being optically inserted into empty levels lying within the amorphous silicon mobility gap. Using modulated photocurrent methods we have determined that these states also dominate the electron deep trapping in this material. We argue that these states arise from defects at the crystalline-amorphous boundary.

Type
Research Article
Copyright
Copyright © Materials Research Society 1999

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