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978-3-8439-0973-0, Reihe Physik
Manipulation of the Emission from Natural and Stranski-Krastanow InGaAs Quantum Dots by Strain
86 Seiten, Dissertation Universität Hamburg (2012), Softcover, A5
This thesis presents experimental results of strain-induced changes in the photoluminescence of indium gallium arsenide (InGaAs) quantum dots in a gallium arsenide (GaAs) matrix. To experimentally control their strain state, the quantum dots are embedded in micrometer-sized cantilevers which can be in situ bend by a piezo-driven glass needle.
In the first part we investigate natural InGaAs quantum dots, i.e., shallow confinements in all three directions for charges in the wetting layer. Due to their weak confinement the photoluminescence of natural InGaAs quantum dots is energetically indistinguishable from the band-gap photoluminescence of the wetting layer in the unstrained state. We demonstrate that the application of strain can separate the natural quantum dot emission energy from the wetting-layer emission by several meV. We explain this observation by means of micro-mechanical simulations combined with analytical models considering strain-induced band-gap shifts as well as the quantum-confined Stark effect caused by shear-strain-induced piezoelectric fields.
In the second part we investigate the fine-structure splitting of InGaAs quantum dots grown in the Stranski-Krastanow mode. We show that strain causes not only a change of the emission energy of the quantum dot transitions but also of both the size and the polarization axis of the fine-structure splitting. This arises from a strain-induced deformation of the confining potential.