Theory of electron-hole pair excitations in semiconductor quantum dots.

Persistent Link:
http://hdl.handle.net/10150/185516
Title:
Theory of electron-hole pair excitations in semiconductor quantum dots.
Author:
Hu, Yuan Zheng.
Issue Date:
1991
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This dissertation considers one- and two-electron-hole-pair excitations in ideally spherical semiconductor quantum dots with infinite or finite confinement potentials. The optical absorption edge of the semiconductor micsrocrystallites is found to be higher than that in the corresponding bulk semiconductor. This blue shift is approximately proportional to 1/R², where R is the radius of the semiconductor microspheres. For small quantum dots with infinite confinement potential, the energies and wave-functions of quantum confined excitons and biexcitons are computed using a numerical matrix diagonalization method. Both numerical matrix digaonalization and perturbative calculations prove that the binding energy of biexcitons is strictly positive regardless of material parameters. A general formula for the optical susceptibility of quantum dots is derived, from which, optical spectra are computed. The theoretical results qualitatively agree with recent experimental observations. Some novel optical properties of quantum dots are revealed by this study, such as the existence of excited biexciton states energetically above the exciton ground state resonance and modified optical nonlinearities. Extending our numerical scheme, we compute the effects of impurities or crystal defects in a simple model. The calculation shows that charge defects or impurities have only a small influence on the optical spectra of quantum dots. The details of the quantum confinement conditions, such as the finite value of the quantum confinement potential and different electron-hole masses inside and outside the dot, are studied within the framework of the variational scheme. Finally, we extend the numerical matrix diagonalization method to investigate the valence band coupling effect in quantum dots by including the Luttinger Hamiltonian. It is found that the concept of heavy- and light-hole has to be modified to describe the hole states in semiconductor quantum dots. Also, the valence band mixing due to spin-orbit interaction changes significantly the optical selection rules and consequently influences the allowed optical excitations in quantum dots.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic; Optics; Condensed matter.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Physics; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Koch, Stephan W.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleTheory of electron-hole pair excitations in semiconductor quantum dots.en_US
dc.creatorHu, Yuan Zheng.en_US
dc.contributor.authorHu, Yuan Zheng.en_US
dc.date.issued1991en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis dissertation considers one- and two-electron-hole-pair excitations in ideally spherical semiconductor quantum dots with infinite or finite confinement potentials. The optical absorption edge of the semiconductor micsrocrystallites is found to be higher than that in the corresponding bulk semiconductor. This blue shift is approximately proportional to 1/R², where R is the radius of the semiconductor microspheres. For small quantum dots with infinite confinement potential, the energies and wave-functions of quantum confined excitons and biexcitons are computed using a numerical matrix diagonalization method. Both numerical matrix digaonalization and perturbative calculations prove that the binding energy of biexcitons is strictly positive regardless of material parameters. A general formula for the optical susceptibility of quantum dots is derived, from which, optical spectra are computed. The theoretical results qualitatively agree with recent experimental observations. Some novel optical properties of quantum dots are revealed by this study, such as the existence of excited biexciton states energetically above the exciton ground state resonance and modified optical nonlinearities. Extending our numerical scheme, we compute the effects of impurities or crystal defects in a simple model. The calculation shows that charge defects or impurities have only a small influence on the optical spectra of quantum dots. The details of the quantum confinement conditions, such as the finite value of the quantum confinement potential and different electron-hole masses inside and outside the dot, are studied within the framework of the variational scheme. Finally, we extend the numerical matrix diagonalization method to investigate the valence band coupling effect in quantum dots by including the Luttinger Hamiltonian. It is found that the concept of heavy- and light-hole has to be modified to describe the hole states in semiconductor quantum dots. Also, the valence band mixing due to spin-orbit interaction changes significantly the optical selection rules and consequently influences the allowed optical excitations in quantum dots.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academicen_US
dc.subjectOpticsen_US
dc.subjectCondensed matter.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorKoch, Stephan W.en_US
dc.contributor.committeememberFalco, Charles M.en_US
dc.contributor.committeememberMcIntyre, Laurence C.en_US
dc.contributor.committeememberRafelski, Johannen_US
dc.identifier.proquest9136847en_US
dc.identifier.oclc710854592en_US
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