Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Nancy M. Haegel, John Powers. Includes bibliographical references (p. 53-54). Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Russell D. Dupuis. Vita. Includes bibliographical references. Available also from UMI Company.

In this thesis, the carrier localization effect, the quantum confinement Stark effect (QCSE) and nonlinear optical properties of the as-grown InGaN/GaN multiple-quantum-wells (MQWs) structure and nanopillars with diameters of 100 nm and 160 nm and height of 700 nm have been investigated with linear and nonlinear photoluminescence (PL) techniques, In order to investigate the carrier localization effect and QCSE, “S-shaped” temperature dependent PL peak positions of the samples are quantitatively simulated and analyzed with the localized-state ensemble luminescence model. It is found that after nanotexturing both the carrier localization effect and QCSE become weakened. Moreover, the smaller the pillars the weaker the two effects will be. In addition, the nanotexturing introduced the new radiative recombination pathways of carriers are confirmed on the sidewalls of the nanopillars with cathodoluminescence (CL) spectrum and panchromatic CL image. Two-photon absorption (TPA) induced PL spectra of the three samples are measured to investigate the nonlinear optical properties. A peculiar excitation-power dependence, say I~P1.53, of the PL intensity is revealed. It was proposed that a mixed excitation mechanism, namely two-step successive one-photon absorption occurring in the InGaN well layers and one-step two-photon absorption mainly taking place in the GaN barrier and buffer layers, to interpret the observed phenomenon. Besides, the steady-state energetic distribution of carriers excited via this mixed excitation mechanism is very different from that of carriers via one-step one-photon excitation. In contrast with the case of one-photon PL in the samples, the influence of carrier localization effect becomes weaker in the TPA PL of the two nanopillars. / published_or_final_version / Physics / Master / Master of Philosophy

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Our previous computational studies of two-dimensional quantum waveguide structures formed at the interface of the A1GaAs/GaAs heterostructure have focused on systems with centered attractive potential wells. From those studies we direct our attention to the quantum waveguide structures with an attractive potential well placed asymmetrically in the transverse direction. In particular, we are interested in the conductance spectrum for higher energy regimes where Fano resonances are the dominant resonance form. Of interest is the change and progression of Fano resonance peaks as a function of both the potentials' depth and offset, especially as it relates to the Breit-Wigner resonance forms observed in lower energy regimes. To accomplish this, the hard-wall models and Fortran code in our previous work have been expanded to include the asymmetrical positioning through solving the single-electron Schrodinger and associated equations used in the tight-binding Hamiltonian and recursive Green's functions. The observed Fano resonance structures are fitted to their characteristic equations through the use of zero-pole pairs. / Department of Physics and Astronomy

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Thesis (Ph. D.)--Ohio University, November, 1991. / Title from PDF t.p.