Energy relaxation dynamics of hot electrons in satellite and upper conduction bands in gallium arsenide and gallium phosphide.
Item
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Title
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Energy relaxation dynamics of hot electrons in satellite and upper conduction bands in gallium arsenide and gallium phosphide.
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Identifier
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AAI9618051
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identifier
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9618051
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Creator
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Cavicchia, Michael Angelo.
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Contributor
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Adviser: Robert R. Alfano
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Date
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1996
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Optics | Physics, Condensed Matter
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Abstract
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An experimental investigation of the energy relaxation dynamics of high-energy, high-density, electron distributions in the satellite and upper conduction band valleys of GaAs and GaP has been performed. UV and visible pump-IR probe absorption spectroscopy was used to observe the dynamics of hot electrons directly in the time domain. The visible pump pulses were obtained directly from an amplified, mode-locked dye laser, the UV pump pulses were obtained by second harmonic generation of the dye laser pulses, and the IR probe pulses were generated by difference frequency mixing of the dye laser pulses with supercontinuum pulses.;For UV photoexcitation, the hot electrons are sufficiently energetic to scatter into the second conduction band valley at the X point of the Brillouin zone, i.e., the X{dollar}\sb7{dollar} valley. By performing measurements of the time-resolved free carrier absorption spectrum the mobility of the hot electrons was determined to be significantly reduced by rapid intervalley scattering from the second conduction band to the first conduction band.;Measurements of the temporal behavior of the {dollar}\rm X\sb6\rightarrow X\sb7{dollar} direct interconduction band absorption (ICA) provided a detailed insight into the electron population dynamics of the X{dollar}\sb6{dollar} and X{dollar}\sb7{dollar} valleys. The intervalley scattering times involving the second conduction band in GaAs were determined from the best fit of a rate equation model to the experimental data. In the GaP, the cooling of the hot electron distributions in the X{dollar}\sb6{dollar} and X{dollar}\sb7{dollar} valleys were directly observed.;Measurements of the induced IR absorption spectra were performed for different photoexcited carrier densities. Lineshape fits of the spectra provided details on the density dependence of the intervalley scattering out of the initially excited states in the {dollar}\Gamma\sb6{dollar} valley into the X{dollar}\sb6{dollar} and X{dollar}\sb7{dollar} valleys. Energy band renormalization and a Burstein-Moss shift were observed in the X{dollar}\sb6{dollar} and X{dollar}\sb7{dollar} valleys in both GaAs and GaP.;The temperature dependence of intervalley scattering from the X{dollar}\sb6{dollar} valley into the lower energy L{dollar}\sb6{dollar} and {dollar}\Gamma\sb6{dollar} valleys in GaAs. The results were compared to recent theoretical calculations. It was determined that L-point transverse acoustic phonons play a stronger role in the intervalley scattering than previously predicted by theory.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
