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Dopage par modulation d'hétérostructures de semiconducteurs II-VI semimagnétiques en épitaxie par jets moléculaires

Abstract : A theoretical preliminary study to this thesis has shown that when a two-dimensional (2D) hole gas is introduced in a semimagnetic semiconductor quantum well, the interaction between the localised spins and the charge carriers induce a ferromagnetic phase transition. We have elaborate such heterostructures, based on tellurides, by molecular beam epitaxy. We have also characterised the interfaces at microscopic level, and we have controlled the doping levels and the charge transfer into the quantum wells. This allowed us to elaborate samples on which a series of physical studies could be done. Modulation doping of II-VI tellurium based semiconductor heterostructures by molecular beam epitaxy had been realised only for n-type doping on CdMgTe barriers with low magnesium content until our study. This alloy is however a key to obtain of a good quantum confinement in tellurides, especially for p-type doping, where higher Mg contents are needed. The use of an ECR nitrogen plasma source, which is a p-type dopant, and the optimisation of growth parameters allowed us to obtain a 2D hole gas of good density, as confirmed by optical spectroscopy, Hall effect and capacitance-voltage measurements. The study of interdiffused structures by SIMS, x-ray diffraction and optical spectroscopy allowed us to understand the degradation mechanisms during the growth of our layers containing both magnesium and nitrogen. A model based on nitrogen diffusion has been proposed. It has then been possible to realise semimagnetic structures in which the interaction between a 2D hole gas and localised manganese spins allowed us to put into evidence the theoretically foreseen ferromagnetic transition. In parallel, we have been testing with success aluminum as a new n-type dopant for molecular beam epitaxy, in thick layers and heterostructures. It can be used more widely than other dopants used until now. In particular, it allows good doping levels even in magnesium-containing layers.
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https://tel.archives-ouvertes.fr/tel-00002701
Contributor : Alexandre Arnoult <>
Submitted on : Wednesday, April 9, 2003 - 10:04:16 AM
Last modification on : Tuesday, September 11, 2018 - 11:00:02 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:08:37 PM

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  • HAL Id : tel-00002701, version 1

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Alexandre Arnoult. Dopage par modulation d'hétérostructures de semiconducteurs II-VI semimagnétiques en épitaxie par jets moléculaires. Physique [physics]. Université Joseph-Fourier - Grenoble I, 1998. Français. ⟨tel-00002701⟩

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1998