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Les dispositifs microélectroniques réalisés en technologie silicium possèdent des limitations intrinsèques liées à ce matériau et ses dérivés (Si, SiO2, SiGe…). Une des solutions pour proposer à l’avenir des performances accrues passe par l’introduction de nouveaux matériaux en technologie silicium. De bons candidats pour le remplacement du silicium en tant que canal de conduction sont les semi-conducteurs III-V à base d’arséniures (III-As) pour bénéficier de leurs propriétés de transport électronique exceptionnelles. Cependant, en préliminaire à la réalisation de tels dispositifs, il faut obtenir des couches de III-As de bonne qualité cristalline sur des substrats de silicium. Ces deux matériaux montrent en effet des différences de propriétés que l’on se propose de surmonter au cours de ces travaux par des stratégies de croissance cristalline.Ces travaux de thèse portent sur l’étude en détail des croissances de couches de matériaux GaAs et InGaAs, sur des substrats de silicium de 300 mm de diamètres et par épitaxie en phase vapeur aux organométalliques. Dans un premier temps, des efforts seront menés afin d’éliminer un des défauts cristallins les plus rédhibitoires pour l’utilisation de ces matériaux, à savoir les parois d’antiphase. Puis, la réalisation d’hétérostructures quantiques III-As permettra, via des analyses d’émissions optiques (photo- et cathodoluminescence), de rendre compte de la qualité globale ainsi que locale des couches ainsi épitaxiées. Enfin, des croissances localisées dans des motifs décananométriques préalablement réalisés sur les substrats de silicium seront conduites dans le but de comprendre les mécanismes de réduction des défauts pour ces géométries. / The microelectronic devices designed in the silicon technology field are intrinsically limited due to the nature of this material and its derivatives (Si, SiO2, SiGe…). One of the solutions to further reach enhanced performances lies in the introduction of new materials within silicon technology. Good candidates for silicon replacement as a conduction channel are the arsenide-based III-V semiconductors (III-As), in order to benefit from their outstanding electronic transfer properties. However, as a preliminary for the achievement of such devices, III-As films with good crystalline quality have to be obtained on silicon substrates. Indeed, those two materials display properties differences this work intends to overcome by following crystalline growth strategies.This PhD work deeply study the growth of GaAs and InGaAs films on 300 mm-diameter silicon substrates by metalorganic vapour phase epitaxy. In the first instance, efforts will be put on the elimination of one of the crystalline defects being the most prohibitive for the use of such materials: antiphase boundaries. Then, the achievement of III-As quantum heterostructures will enable, by optical emission analysis (photo- and cathodoluminescence), to reflect the global and local quality of the resultant epitaxial films. Finally, localised growth, in decananometric designs, preliminary performed on silicon substrates, will be carried out, with the aim of understanding the defects reduction mechanisms for those geometries.

Avec l’avènement de l’internet des objets, la diversification des moyens de communication et l’augmentation de la puissance de calcul des processeurs, les besoins en termes d’échange de données n’ont cessé d’augmenter. Ces technologies nécessitent de combiner notamment sur un circuit intégré des fonctions optiques et RF réalisées à partir de matériaux III-V avec des fonctions logiques en silicium. Cependant en pré requis à la réalisation de ces dispositifs, il faut obtenir des couches de III-V sur des substrats de silicium avec une bonne qualité structurale et savoir former des contacts de type n et p avec une faible résistivité. L’objectif de cette thèse est d’intégrer sur silicium du GaAs car ce matériau est couramment employé dans fabrication d’émetteurs et de récepteurs pour les communications sans fils ainsi que dans la conception de LEDs et de lasers. Dans cette optique, ces travaux de thèse proposent donc d’étudier la croissance de GaAs sur des substrats de silicium de 300 mm par épitaxie en phase vapeur aux organométalliques et sur la formation de contacts n et p avec une faible résistivité sur ce même GaAs. En premier lieu, des études seront menées pour pouvoir s’affranchir des défauts générés durant la croissance du GaAs sur silicium (parois d’antiphase et dislocations émergentes). Par la suite, des caractérisations structurales (diffraction par rayons X, FIB STEM), morphologiques (AFM), électriques (effet hall) et optiques (photoluminescence) permettront de rendre compte de la qualité du matériau et de l’impact de ces défauts. Enfin, l’évolution des propriétés (optiques et de transport) du GaAs ainsi que la formation de contacts de type n et p avec une faible résistivité sera abordée. / With the emergence of Internet of Things (IoT), diversification of communication means and rise of processors’ computational power, the requirements in data exchange never stopped rising. These technologies need to combine on integrated circuits, optical and RF purposes fabricated from III-V compounds with silicon logical functions. However, as preliminary for the achievement of such devices, III-V semiconductors with good crystal quality have to be obtained on silicon substrates and formation of n & p type contacts with low resistivity is required. The purpose of this thesis is to integrate GaAs on silicon because this semiconductor is frequently used for the fabrication of emitters and receptors for wireless communication as well as in LEDs and lasers’ conception. With this is mind, this PhD work focuses on the growth of GaAs on 300 mm silicon substrates by metalorganic chemical vapour deposition and the formation of n & p type contacts with low contact resistivity on this GaAs. Firstly, efforts will put on the removal of the crystalline defects being the most prohibitive for the use of such materials: antiphase boundaries and threading dislocations. Then, structural (X-ray diffraction, FIB STEM), morphological (AFM), electrical (Hall Effect) and optical (photoluminescence) characterizations will highlight the quality of the epitaxial films. Finally, the evolution of GaAs properties (optical and transport) and the formation of n & p-type contacts with low resistivity will be discussed.

The thesis is primarily concerned with the design, construction and preliminary commissioning of a novel polarimeter for full three-dimensional analysis of electron spin polarisation. The polarimeter is described in detail, together with the theoretical basis for its operation. Studies of an amorphous ferromagnetic alloy, Co66Fe4Ni1B14Si15, and its application as a secondary standard are presented. Finally, a design study of a GaAs polarised electron source, capable of providing both longitudinal and transverse polarisations, is detailed.

We investigate the electronic band structure of device relevant GaInNAs/GaAs multiple quantum wells (MQWs) and veitical-cavity surface-emitting laser (VCSEL) structures. We report photo-modulated reflectance (PR) studies under applied pressure and variable temperature that probe the influence of N-related states on the electronic structure of dilute nitrogen (N) III-V MQWs. The pressure and temperature dependence of the intersubband transitions within the MQWs is reduced by addition of N. By matching our experimental results with a theoretical model important predictions for the ground-state electron effective mass and conduction band offset as a function of N and pressure are made. We present results of angle- and temperature-dependent electro-reflectance (ER) measurements on a dilute-N GaInNAs VCSEL and show that these explain how the corresponding VCSEL device can operate over a such a wide range of temperatures. We argue that intrinsic properties of dilute-N QWs provide novel ways to design laser devices, especially in the crucial telecommunication range of wavelengths. We show how non-destructive ER and PR measurements can be used, in order to estimate the QW transition energy when it is coupled with the cavity mode (CM). The energy of the main exciton is determined by monitoring the amplitude and the phase of the PR spectra. The ER measurements are presented on the GaInNAs VCSEL described in the previous paragraph. Furthermore we present a growth characterisation study on a representative InGaAs/GaAs/AlAs/AlGaAs as-grown VCSEL structure, using PR spectroscopy as a function of position on a non-uniform wafer. We also show how temperature dependent PR and the appropriate lineshape model can be used to obtain a full picture of the relative movements between the gain and the CM over the full range of temperature. This information allows calculating the material gain in the temperature range of interest, independent from the effect of the CM and also provides an alternative method for characterising the growth, which can be applied to uniform wafers. PR and non-destructive ER can be used to identify regions suitable for fabrication into devices. For this reason modulation spectroscopy can be very useful for industry to reject wafers where good alignment between the CM and the QW does not occur and can thus save on the time consuming and expensive fabrication procedures.

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No description available.

Nuclear Magnetic Resonance (NMR) has been a fundamental player in the studies of superconducting materials for many decades. This local probe technique allows for the study of the static electronic properties as well as the low energy excitations of the electrons in the normal and the superconducting state. On that account it has also been widely applied to Fe-based superconductors from the very beginning of their discovery in February 2008. This dissertation comprises some of these very first NMR results, reflecting the unconventional nature of superconductivity and its strong link to magnetism in the investigated compounds LaO(1-x)F(x)FeAs and LiFeAs.

Nuclear Magnetic Resonance (NMR) has been a fundamental player in the studies of superconducting materials for many decades. This local probe technique allows for the study of the static electronic properties as well as the low energy excitations of the electrons in the normal and the superconducting state. On that account it has also been widely applied to Fe-based superconductors from the very beginning of their discovery in February 2008. This dissertation comprises some of these very first NMR results, reflecting the unconventional nature of superconductivity and its strong link to magnetism in the investigated compounds LaO(1-x)F(x)FeAs and LiFeAs.:1. Introduction 2. Basic Principles of NMR 3. NMR in the Superconducting State 4. Iron-based Superconductors 5. Experimental Setup 6. NMR on LaO(1-x)F(x)FeAs in the Normal State 7. MR and NQR on LaO(1-x)F(x)FeAs in the Superconducting State 8. NMR and NQR on LiFeAs 9. Conclusions