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Confinements non-usuels dans les boîtes quantiques semiconductrices

Abstract : This thesis reports on numerical calculations of electronic and optical properties of quantum dots with unusual confinement such as InGaN/GaN dots, CdSe tetrapod,...

After having shown the numerical calculation methods used throughout this work, we begin with a theoretical study on a superlattice of InAs/GaAs quantum dots with a short period. This short period causes a vertical alignment of quantum dots. We show that the ground state couples only with the continuum states which have nearly the same in-plane extension for the excitations with polarization along the growth direction (z). Following these particular couplings, the photo-responses in z polarization do not change when a vertical magnetic field is applied despite numerous quasi-Landau states in the continuum. Next, we show that strong bound-to-continuum absorption with in-plane polarizations is possible if we reduce the planar dimension of the dots. The results above are applied to explain the experimental results obtained by the group in Vienna. In this collaboration work, we study theoretically and experimentally the photo-detectors based on InAs/GaAs quantum dots embedded in a superlattice, with or without AlAs barriers. We show that these periodic structures can be used to fabricate photo-detectors in the far infrared range. The photo-current spectra are in good agreement with calculated optical absorption spectra.

In the next part of the work, we are interested in nitride heterostructures. These semiconductors have original physical properties such as large effective masses, large band offsets, giant piezoelectric field, ... We are interested in particular in InGaN/GaN heterostructures on which numerous optoelectronic applications are based. We show that the disorder effect as well as the large physical parameters make the Virtual Crystal Approximation no more valid in these systems. Finally, the calculations of electronic structures of the CdSe tetrapods are performed. We show that the first four states are well confined in the spherical body, which is coherent with the experiments.
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Submitted on : Friday, January 13, 2006 - 10:53:52 AM
Last modification on : Thursday, December 10, 2020 - 12:36:52 PM
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  • HAL Id : tel-00011374, version 1

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Duc Phuong Nguyen. Confinements non-usuels dans les boîtes quantiques semiconductrices. Physique [physics]. Université Pierre et Marie Curie - Paris VI, 2005. Français. ⟨tel-00011374⟩

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