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Résumé

Les thèmes de recherche développés dans cette habilitation portent sur les lasers à cavité verticale (VCSELs) dans la gamme de longueur d'onde 0,85-1,55 m. La géométrie particulière de cet émetteur et son attractivité dans un contexte applicatif, autant pour son intégrabilité que pour son intérêt économique, a dicté les évolutions récentes des composants VCSEL. L'adaptation de cet émetteur aux multiples usages ambitionnés par les industriels a incité d'une part à élargir la bande spectrale d'émission, la plus convoitée étant celle des communications optiques, et d'autre part à intégrer sur puce ces composants dans une vision de combinaisons de fonctions élémentaires dans un système optique complexe. Je présenterai les contextes dans lesquels ces deux thématiques de recherche se sont développées, et comment s'y sont articulés mes projets de recherche.

Abstract

The topics of the researches developed in this manuscript turns on vertical cavity lasers (VCSELs) in the wavelength range from 850 to 1550 nm. The particular geometry of this laser emitter, together with its attractiveness in the industrial applications context, regarding integration capabilities and economic interest, have paved the way for the recent evolutions of the VCSEL devices. The adaptation of this emitter to the wide field of industrial applications foreseen has urged in the past years, for one part to widen the emission band spectrum, the most coveted being the telecommunications window, but also to integrate on chip these lasers with the aim of combining elementary functionalities into complex optical systems. I present here the contexts in which these both research axes have been evoluting recently, and how my research activities have been developed within these themes.

Mots-Clés / Keywords

Lasers à cavité verticale; Infrarouge; Optoélectronique; Epitaxie; Technologie; Matériaux; VCSEL; Infrared emitter; Optoelectronics; Epitaxy; Technology; Materials;

Abstract

A thorough study of wet thermal oxidation in AlAs/AlxGa1-xAs superlattices is presented. The results shown here demonstrate that the final oxidation depth can be finely tuned via the composition and thickness of AlxGa1-xAs into the digital alloy. A complete model of oxidation in these structures is proposed, relying on diffusion through the AlAs layer, its oxidation and an additional effect due to the AlxGa1-xAs intermediate barriers. This barrier contribution is shown to further improve the control of the oxidation rate, and thereby fabrication of sophisticated AlOx/GaAs integrated optoelectronic devices.

Abstract

A thorough study of the selective wet oxidation in digital AlxGa1xAs alloys is presented. We report experimental results and physical interpretation on the oxidation kinetics within those ranges of the AlGaAs composition (x = 0.95 to 1) and layer thickness (20 to 50 nm) of interest for oxide-aperture vertical-cavity surface-emitting laser (VCSEL) application. We demonstrate the high controllability of the oxidation reaction between different Al compositions; made different thanks to the use of digital alloys. Unlike standard alloys, we measured an invariability of the oxidation rates in the studied thickness range (2050 nm), implying a better control of the fabrication process. The dependence of the reaction rate with the temperature is expressed as an Arrhenius law. Two activation energies (1.2 and 0.55 eV) have been derived for composition ranges of x = 0.950.98 and x = 0.991, respectively, revealing that two different mechanisms are involved depending on the Al content and the superlattice structure of the digitally-grown AlGaAs.

Mots-Clés / Keywords

Oxide aperture VCSEL; Wet thermal oxidation; AlAs; AlxOy; AlGaAs digital alloy; Oxide confinement;