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Ultrafast Carrier Thermalization in Hydrogenated Amorphous Silicon

Published online by Cambridge University Press:  01 February 2011

S. L. Dexheimer
Affiliation:
Department of Physics, Washington State University, Pullman, WA
C. P. Zhang
Affiliation:
Department of Physics, Washington State University, Pullman, WA
J. Liu
Affiliation:
Department of Physics, Washington State University, Pullman, WA
J. E. Young
Affiliation:
Department of Physics, Washington State University, Pullman, WA
B. P. Nelson
Affiliation:
National Renewable Energy Laboratory, Golden, CO
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Abstract

We present detailed studies of the initial relaxation processes of photoexcited carriers in hydrogenated amorphous silicon. We have carried out time-resolved measurements of the photoexcited carrier response in HWCVD a-Si:H thin films using a wavelength-resolved femtosecond pump-probe technique, in which an intense 35-fs pump pulse excites carriers in the sample and a time-delayed probe pulse measures the resulting change in optical properties as a function of time delay following the pump pulse. Measurements of the transient optical absorbance were carried out as a function of the density of excited carriers, sample temperature, and probe wavelength. These studies indicate fast carrier thermalization via phonon emission on a ∼ 150 fs time scale and rapid phonon equilibration on a ∼ 230 fs time scale.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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