Hot carrier dynamics in the satellite X valley and intervalley scattering in gallium arsenide and aluminum gallium arsenide.
Item
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Title
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Hot carrier dynamics in the satellite X valley and intervalley scattering in gallium arsenide and aluminum gallium arsenide.
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Identifier
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AAI9325162
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identifier
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9325162
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Creator
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Wang, Wubao.
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Contributor
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Adviser: Robert R. Alfano
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Date
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1993
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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, Condensed Matter | Physics, Optics
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Abstract
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The time evolution of the population of hot electrons in the k {dollar}\ne{dollar} 0 satellite X valley in GaAs and AlGaAs has been directly measured for the first time by a femtosecond visible-pump and IR-probe absorption spectroscopy. The {dollar}L\to\Gamma{dollar} and {dollar}X\to\Gamma{dollar} intervalley scattering was found to act as a source of heating of electrons in the {dollar}\Gamma{dollar} valley. This enables us to determine corresponding intervalley scattering rates from the measured carrier dynamics. The measured temporal and spectral profiles of the induced IR absorption have also been used to determine band structure parameters for GaAs and AlGaAs.;The time-resolved IR absorption subsequent to the excitation at 527 nm in GaAs was measured. The rate equation analysis involving the intra-and-intervalley scattering are used to determine the {dollar}X\sb6\to\Gamma\sb6{dollar} intervalley scattering time of {dollar}\sim{dollar}500 fs.;The transient {dollar}X\sb6\to X\sb7{dollar} band-to-band IR absorption spectrum in GaAs was measured by varying IR probe wavelengths, from which the energy gap between the minima of the {dollar}X\sb6{dollar} and {dollar}X\sb7{dollar} bands has been directly determined to be 0.345 {dollar}\pm{dollar} 0.017 eV, and the density of states effective mass for the {dollar}X\sb7{dollar} band has been found to be 0.48 {dollar}\pm{dollar} 0.06 m{dollar}\sb0.{dollar}.;The temperature dependence of hot electron relaxation in GaAs has been observed in a range from 4K to 300K. The much longer relaxation time of hot electrons at low temperature comparing with that at room temperature is attributed to the reduction of the number of phonons participating in the electron-phonon interaction.;The time evolution of the population of hot electrons in the bottom of the X valley in {dollar}Al\sb{lcub}0.6{rcub}Ga\sb{lcub}0.4{rcub}As{dollar} was measured, and the {dollar}L\sb6\to X\sb6{dollar} intervalley scattering time of {dollar}\sim{dollar}200 fs was determined. Both phonon-assisted and alloy-disorder-induced intervalley scatterings were considered and the {dollar}L\sb6 - X\sb6{dollar} intervally deformation potential of {dollar}{lcub}\sim{rcub}2.7 \times 10\sp8{dollar} eV/cm has been determined.;The temporal profiles of the IR absorption for five {dollar}Al\sb{lcub}x{rcub}Ga\sb{lcub}1-x{rcub}As{dollar} samples were measured. The dynamics of the X valley electrons for samples with {dollar}x\le 0.408{dollar} was found to be different from that for samples with {dollar}x\ge 0.439{dollar} which reflects their different types of band gaps. The critical value of {dollar}x\sb{lcub}c{rcub}{dollar} which corresponds to direct-to-indirect band gap transition for {dollar}Al\sb{lcub}x{rcub}Ga\sb{lcub}1-x{rcub}As{dollar} was determined to be 0.412 {dollar}\pm{dollar} 0.009.
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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.
