Semiconductor lasers based on gallium arsenide and relatedmaterials are widely used in applications such as opticalcommunication systems, sensing, compact disc players, distancemeasurement, etc. The performance of these lasers can beimproved using a buried heterostructure offering lateralcarrier and optical confinement. In particular, if theconfinement (burying) layer is implemented by epitaxialregrowth of an appropriate aluminium-free semi-insulating (SI)material, passivation of etched surfaces, reduced tendency tooxidation, low capacitance and integration feasibility areadditional advantages. The major impediment in the fabrication of GaAs/AlGaAsburied-heterostructure lasers is the spontaneous oxidation ofaluminium on the etched walls of the structure. Al-oxide actsas a mask and makes the regrowth process extremely challenging.In this work, a HCl gas-basedin-situcleaning technique is employed successfully toremove Al-oxide prior to regrowth of SI-GaInP:Fe and SI-GaAs:Fearound Al-containing laser mesas by Hydride Vapour PhaseEpitaxy. Excellent regrowth interfaces, without voids, areobtained, even around AlAs layers. Consequences of usinginadequate cleaning treatments are also presented. Regrowthmorphology aspects are discussed in terms of different growthmechanisms. Time-resolved photoluminescence characterisation indicates auniform Fe trap distribution throughout the regrown GaInP:Fe.Scanning capacitance microscopy measurements demonstrate thesemi-insulating nature of the regrown GaInP:Fe layer. Thepresence of EL2 defects in regrown GaAs:Fe makes more difficultthe interpretation of the characterisation results in the nearvicinity of the laser mesa. GaAs/AlGaAs buried-heterostructure lasers, both in-planelasers and vertical-cavity surface-emitting lasers, withGaInP:Fe as burying layer are demonstrated for the first time.The lasers exhibit good performance demonstrating thatSI-GaInP:Fe is an appropriate material to be used for thispurpose and the suitability of our cleaning and regrowth methodfor the fabrication of this type of semiconductor lasers.Device characterisation indicates negligible leakage currentalong the etched mesa sidewalls confirming a smooth regrowthinterface. Nevertheless, experimental and simulation resultsreveal that a significant part of the injected current is lostas leakage through the burying material. This is attributed todouble carrier injection into the SI-GaInP:Fe layer.Simulations also predict that the function of GaInP:Fe ascurrent blocking layer should be markedly improved in the caseof GaAs-based longer wavelength lasers. <b>Keywords:</b>semiconductor lasers, in-plane lasers, VCSELs,GaAs, GaInP, semi-insulating materials, hydride vapour phaseepitaxy, regrowth, buried heterostructure, leakage current,simulation.

<p>Semiconductor lasers based on gallium arsenide and relatedmaterials are widely used in applications such as opticalcommunication systems, sensing, compact disc players, distancemeasurement, etc. The performance of these lasers can beimproved using a buried heterostructure offering lateralcarrier and optical confinement. In particular, if theconfinement (burying) layer is implemented by epitaxialregrowth of an appropriate aluminium-free semi-insulating (SI)material, passivation of etched surfaces, reduced tendency tooxidation, low capacitance and integration feasibility areadditional advantages.</p><p>The major impediment in the fabrication of GaAs/AlGaAsburied-heterostructure lasers is the spontaneous oxidation ofaluminium on the etched walls of the structure. Al-oxide actsas a mask and makes the regrowth process extremely challenging.In this work, a HCl gas-based<i>in-situ</i>cleaning technique is employed successfully toremove Al-oxide prior to regrowth of SI-GaInP:Fe and SI-GaAs:Fearound Al-containing laser mesas by Hydride Vapour PhaseEpitaxy. Excellent regrowth interfaces, without voids, areobtained, even around AlAs layers. Consequences of usinginadequate cleaning treatments are also presented. Regrowthmorphology aspects are discussed in terms of different growthmechanisms.</p><p>Time-resolved photoluminescence characterisation indicates auniform Fe trap distribution throughout the regrown GaInP:Fe.Scanning capacitance microscopy measurements demonstrate thesemi-insulating nature of the regrown GaInP:Fe layer. Thepresence of EL2 defects in regrown GaAs:Fe makes more difficultthe interpretation of the characterisation results in the nearvicinity of the laser mesa.</p><p>GaAs/AlGaAs buried-heterostructure lasers, both in-planelasers and vertical-cavity surface-emitting lasers, withGaInP:Fe as burying layer are demonstrated for the first time.The lasers exhibit good performance demonstrating thatSI-GaInP:Fe is an appropriate material to be used for thispurpose and the suitability of our cleaning and regrowth methodfor the fabrication of this type of semiconductor lasers.Device characterisation indicates negligible leakage currentalong the etched mesa sidewalls confirming a smooth regrowthinterface. Nevertheless, experimental and simulation resultsreveal that a significant part of the injected current is lostas leakage through the burying material. This is attributed todouble carrier injection into the SI-GaInP:Fe layer.Simulations also predict that the function of GaInP:Fe ascurrent blocking layer should be markedly improved in the caseof GaAs-based longer wavelength lasers.</p><p><b>Keywords:</b>semiconductor lasers, in-plane lasers, VCSELs,GaAs, GaInP, semi-insulating materials, hydride vapour phaseepitaxy, regrowth, buried heterostructure, leakage current,simulation.</p>

Cette thèse est consacrée à l’étude de l’outil d’épitaxie HVPE (Hydride Vapour Phase Epitaxy) pour la synthèse avec et sans catalyseur de nanofils semiconducteurs GaN et GaAs. Une étude systématique de l’influence des conditions expérimentales sur la croissance des fils de GaN est effectuée, afin de démontrer la faisabilité de cette croissance sur la surface des substrats saphir plan-c et silicium sans aucun traitement de la surface préalablement à la croissance. Nous avons démontré la croissance par VLS-HVPE, de nanofils de GaN de diamètres constants de 40 à 200 nm, de longueurs supérieures à 60 μm et présentant des qualités optique et cristallographique remarquables. Pour les nanofils de GaAs, la stabilité, inédite, de la phase cubique zinc-blende pour des diamètres de 10 nm a été démontrée par le procédé de croissance VLS-HVPE sur des longueurs de quelques dizaines de micromètres. Les mécanismes de croissance sont discutés à partir des diagrammes de phase et de la physique de la croissance HVPE qui met en oeuvre des précurseurs gazeux chlorés. Pour les semiconducteurs III-V, cette étude permet d’envisager des applications liées aux nanofils longs qui jusque là n’étaient exploitées que pour le silicium. Ces travaux montrent que dans le contexte des Nanosciences, la HVPE, outil épitaxial à fortes vitesses de croissance, mérite une audience élargie, et peut s’inscrire comme un outil complémentaire efficace aux procédés MOVPE et MBE pour le façonnage contrôlé de la matière à l’échelle nanométrique. / This thesis is devoted to the study of HVPE (Hydride Vapour Phase Epitaxy) method of growing GaN and GaAs nanowires with and without catalyst. A systematic study of the influence of the growth conditions on GaN formation was performed in order to demonstrate the feasibility of this growth on c-plane sapphire and silicon substrates without preliminary treatment of the surface. We have demonstrated by VLS-HVPE the growth of the GaN nanowires with constant diameters of 40 to 200 nm and of length up to 60 μm, while they possess remarkable optical and crystal quality. The newly observed stability of the zinc blende structure for GaAs nanowires with diameters of 10 nm has been described by the VLS-HVPE process, for lengths of few tens of micrometers. The growth mechanisms are discussed based on the phase diagram and the physics of near-equilibrium HVPE using chloride precursors. For III-V semiconductors, the study allows us to consider applications related to long nanowires that, at present, are used only for silicon. This work shows that in the context of Nanoscience, the fast growth HVPE method deserves a wider audience and thus could be considered as an effective complementary tool to MOVPE and MBE processes for the controlled shaping of matter on the nanoscale.