Carrier and exciton dynamics in strained semiconductor bulk and quantum wells.
Item
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Title
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Carrier and exciton dynamics in strained semiconductor bulk and quantum wells.
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Identifier
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AAI9521318
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identifier
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9521318
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Creator
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Takiguchi, Yoshihiro.
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Contributor
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Co-Advisers: Kai Shum | Robert R. Alfano
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Date
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1995
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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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Engineering, Electronics and Electrical | Physics, Optics | Physics, Condensed Matter
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Abstract
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In this thesis, I have investigated carrier and exciton dynamics in built-in and/or externally strained semiconductor bulk and quantum well samples at 4 to 300{dollar}\sp\circ{dollar}K lattice temperatures. Their band structures were altered by a combination of the stress and the quantum confinement. I have examined the photoluminescence kinetics in time and energy domains using picosecond time-resolved photoluminescence spectroscopy.;I investigated the hole thermalization and cooling processes in 2{dollar}\mu{dollar}m and 4{dollar}\mu{dollar}m thick n-type GaAs epilayers grown on Si substrates. I found the hole temperature decreased exponentially with the cooling time of 28 ps and the cooling rate of 0.115 meV/ps. The time was about six times slower than the theoretically expected rate due to the non-equilibrium LO phonon accumulation in the system.;I investigated the electron thermalization and cooling process in beryllium modulation-doped multiple quantum wells (MQWs) with 40A and 188A well widths fabricated on Si substrates. I determined the electron cooling times and rates to be {dollar}46\pm4{dollar} ps and 0.2 meV/ps in the 188A MQW/Si and 30 ps and 0.2 meV/ps in the 40A MQW/Si, respectively. The external uniaxial compressive stress applied onto the 188A MQW/Si changed the electron cooling time.;I investigated the exciton dynamics in a 188A single QW/Si (SQW/Si) under external uniaxial compressive stress and in a biaxial tensioned GaAsP QWs. The intrinsic 188A SQW/Si under uniaxial compression showed a fast and a slow energy relaxation processes arising from the exciton-LO phonon interaction and the inter-subband scattering, respectively. In the GaAsP QWs, the photogenerated carriers were found to form excitons within 30 ps and the exciton relaxes down to the lowest energy level through intra- and inter-subband scattering within 30 ps to 100 ps depending on the well width, the exciton mass, and the lattice temperature. The exciton localization process into the interface islands was found to consist of a fast acoustic deformation potential interaction and a slow exciton trapping process to the widest island which is regarded as quasi-zero dimensional square wells.
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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.
