Carrier LO Phonon Interactions in InAs/GaAs Quantum Dots:
Electronic Polarons and Excitonic Polarons

Abstract : This thesis presents a study of electrons, holes and excitons confined in self-assembled InAs/GaAs quantum dots. The interaction of these confined carriers with the longitudinal optical (LO) phonons of the surrounding crystal lattice is investigated. It is found that this interaction leads to the formation of the so-called quantum dot polarons; hybrid carrier phonon states which are the true excitations of a charged dot.
The first part of this thesis describes the results of far
infrared (50 - 700 cm-1) magnetospectroscopy experiments performed on n- and p-doped samples. The intraband energy levels of these systems are probed. The magnetic field is an important experimental parameter, as it allows for the evolution of the energy levels, necessary for the observation of electronic
and hole polaron levels. Using the Fröhlich Hamiltonian, which couples the phonon and purely electronic states, the energy levels and oscillator strengths of the system are determined. For both the investigation of electrons and holes confined in dots, a good agreement is found between the calculations and the experimental results.

The second part of this thesis is dedicated to the study of the interaction between electron-hole pairs or excitons and the phonons of the lattice. The interband energy transitions of the dots are investigated using photoluminescence excitation and resonant photoluminescence spectroscopy under strong magnetic
fields up to 28 T. These techniques allow for the circumvention of the inhomogeneous broadening of the resonances that arise from size and composition fluctuations in the quantum dot ensembles.
The magnetic field dependence of the resonance energies allows for an unambiguous assignment of the interband transitions. The excitonic polaron energies as well as the oscillator strengths of the interband transitions are determined. The calculations
account well for the experimental data.
Document type :
Theses
Physics [physics]. Université Pierre et Marie Curie - Paris VI, 2006. English


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Contributor : Vanessa Preisler <>
Submitted on : Thursday, August 31, 2006 - 4:20:08 PM
Last modification on : Thursday, November 2, 2006 - 3:42:33 PM

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Vanessa Preisler. Carrier LO Phonon Interactions in InAs/GaAs Quantum Dots:
Electronic Polarons and Excitonic Polarons. Physics [physics]. Université Pierre et Marie Curie - Paris VI, 2006. English. <tel-00090546>

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