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Transitions optiques interbandes et intrabandes dans les boites quantiques simples et couplées verticalement

Abstract : After an introduction on the methods used for electronic states calculations, we study electron and hole bound states in a single dot. We initially evaluate the oscillator strength and polarization selection rules for intraband transitions. We show that in a single dot the absorption is very anisotropic, depending on the polarization direction of the incident light. We also develope a model for interpreting some recent STM measurements, which are able to ``image'' single dot wavefunctions. Then we study vertically stacked quantum dot systems. We examine the coupling between the dots of a stack as a function of the barrier thickness. Systems of strongly coupled dots are particularly interesting: we show that the optical anisotropy, typical of single dots, considerably diminishes in this kind of systems. Strongly coupled dots are also interesting when electric field effects are studied. We show that they are as tunable as quantum wells of the same dimensions, when an uniform electric field is applied in the growth direction. In addition to this enhanced Stark tunability, stacked dots present the advantage over quantum wells that no continuum absorption exists. The last part of this work is devoted to a detailed numerical study of the continuum, wetting layer ($2D$) and barrier ($3D$), states. We show that the continuum states have an important role for interband transitions. We show in particular that crossed transitions, which involve bound and continuum states, lead to the appearance of a continuous background in the interband absorption spectrum, in the energy range between the bound-to-bound transitions and the wetting layer absorption edge. The existence of this background, experimentally proved, shows that the ``artificial atom'' model is too simple to describe the features of quantum dot interband spectrum.
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https://tel.archives-ouvertes.fr/tel-00003115
Contributor : Angela Vasanelli <>
Submitted on : Thursday, July 10, 2003 - 4:06:10 PM
Last modification on : Thursday, October 29, 2020 - 3:01:15 PM
Long-term archiving on: : Tuesday, September 11, 2012 - 9:05:17 PM

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  • HAL Id : tel-00003115, version 1

Citation

Angela Vasanelli. Transitions optiques interbandes et intrabandes dans les boites quantiques simples et couplées verticalement. Physique [physics]. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00003115⟩

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