The foundation of vacuum nanoelectronics was laid as early as in 1961 when Kenneth Shoulders proposed the development of vertical field-emission micro-triodes. After years of conspicuous stagnancy in the field much interest has reemerged for the vacuum nanoelectronics in recent years. Electron field emission under high electric field from conventional and exotic nanoemitters, which have now been made possible with the use of modern day technology, has been the driving force behind this renewal of interest in vacuum nanoelectronics. In the research reported in this thesis self-assembled silicon nanostructures were studied as a potential source of field emission for vacuum nanoelectronic device applications. Whiskerlike protruding silicon nanostructures were grown on untreated n- and p-type silicon surfaces using electron-beam annealing under high vacuum. The electrical transport characteristics of the silicon nanostructures were investigated using conductive atomic force microscopy (C-AFM). Higher electrical conductivities for the nanostructured surface compared to that for the surrounding planar silicon substrate region were observed. Non-ideal diode behaviour with high ideality factors were reported for the individual nanostructure-AFM tip Schottky nanocontacts. This demonstration, indicative of the presence of a significant field emission component in the analysed current transport phenomena was also detailed. Field emission from these nanostructures was demonstrated qualitatively in a lift-mode interleave C-AFM study. A technique to fabricate integrated field emission diodes using silicon nanostructures in a CMOS process technology was developed. The process incorporated the nanostructure growth phase at the closing steps in the process flow. Turn-on voltages as low as ~ 0.6 V were reported for these devices, which make them good candidates for incorporation into standard CMOS circuit applications. Reproducible I V characteristics exhibited by these fabricated devices were further studied and field emission parameters were extracted. A new consistent and reliable method to extract field emission parameters such as effective barrier height, field conversion factor, and total emitting area at the onset of the field emission regime was developed and is reported herein. The developed parameter extraction method used a unified electron emission approach in the transition region of the device operation. The existence of an electron-supply limited current saturation region at very high electric field was also confirmed. Both the C-AFM and the device characterization studies were modelled and simulated using the finite element method in COMSOL Multiphysics. The experimental results – the field developed at various operating environments – are explained in relation to these finite element analyses. Field enhancements at the atomically sharp nanostructure apexes as suggested in the experimental studies were confirmed. The nanostructure tip radius effect and sensitivity to small nanostructure height variation were investigated and mathematical relations for the nanostructure regime of our interest were established. A technique to optimize the cathode-opening area was also demonstrated. Suggestions related to further research on field emission from silicon nanostructures, optimization of the field emission device fabrication process, and fabrication of field emission triodes are elaborated in the final chapter of this thesis. The experimental, modelling, and simulation works of this thesis indicate that silicon field emission devices could be integrated into the existing CMOS process technology. This integration would offer goods from both the worlds of vacuum and solid-sate nanoelectronics – fast ballistic electron transport, temperature insensitivity, radiation hardness, high packing density, mature technological backing, and economies of scale among other features.

L'interférométrie à rétro-injection optique, également connu sous le nom de Self-Mixing, permet de concevoir des capteurs qui sont compacts, auto-alignés et sans contact. Dans ce phénomène, une partie du faisceau laser de retour réfléchi par la cible rentre dans la cavité active de laser et fait varier ses propriétés spectrales. La diode laser agit alors comme une source de lumière, un microinterféromètre ainsi qu'un détecteur de lumière. Dans cette thèse, un capteur de déplacement, basé sur la rétro-injection optique, a été optimisé de sorte que des mesures précises peuvent être obtenues en temps réel. Le capteur est robuste à la disparition des franges de self-mixing pour des vibrations harmoniques. Il est également capable de s'adapter à un changement dans le régime de feedback optique et peut donc extraire le déplacement dans les cas les plus répandus expérimentalement, à savoir un feedback faible puis modéré. L'utilisation de l'optique adaptative, sous la forme d'une lentille liquide, a également été démontrée pour ce capteur, ce qui nous a permis de maintenir le capteur dans un régime de feedback favorable. L'influence du speckle a également été réduite de telle sorte que le capteur mesure jusqu'à la gamme centimétrique pour des cibles non- oopératives. Une nouvelle technique est également présentée, elle permet de rendre le capteur insensible aux vibrations mécaniques parasites qui fausseraient la mesure pour des conditions industrielles. / Optical Feedback Interferometry, also known as Self-Mixing, results in compact, selfaligned and contact-less sensors. In this phenomenon, a portion of the laser beam is back reflected from the target and enters the active laser cavity to vary its spectral properties. The laser diode then simultaneously acts as a light source, a micro- nterferometer as well as a light detector. In this thesis, a self-mixing displacement sensor has been optimised so that precise measurement can be obtained in real-time. The sensor is robust to the disappearance of self-mixing fringes for harmonic vibrations. It is also able to auto-adapt itself to a change in the optical feedback regime and so can extract displacement from the weak as well as moderate feedback regime signals. The use of adaptive optics, in the form of a liquid lens, has also been demonstrated for this sensor, which has allowed us to maintain the sensor in a fringe-loss less regime. The influence of speckle has also been reduced so that the sensor can now measure up to the centimetric range for non-cooperative targets. A novel technique has also been presented that makes the sensor insensitive to parasitic mechanical vibrations that would falsify the measurement under industrial conditions.

The objectives of this work were to investigate, design and implement beam steering antenna arrays for mobile and wireless applications using the genetic algorithm (GA) and particle swarm optimisation (PSO) techniques as optimisation design tools. Several antenna designs were implemented and tested: initially, a printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering was investigated. A coplanar waveguide (CPW) to coplanar strip (CPS) transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before it, was proposed. The measured performance of the RF switch was tested and the results confirmed its viability. Then two hybrid coupled PIN diode phase shifters, using Branchline and Rat-Race ring coupler structures, were designed and tested. The generation of four distinct phase shifts was implemented and studied. The variations of the scattering parameters were found to be realistic, with an acceptable ±2 phase shift tolerance. Next, antenna beam steering was achieved by implementing RF switches with ON or OFF mode functions to excite the radiating elements of the antenna array. The switching control process was implemented using a genetic algorithm (GA) method, subject to scalar and binary genes. Anti-phase feeding of radiating elements was also investigated. A ring antenna array with reflectors was modelled and analysed. An antenna of this type for mobile base stations was designed and simulation results are presented. Following this, a novel concept for simple beam steering using a uniform antenna array operated at 2.4 GHz was designed using GA. The antenna is fed by a single RF input source and the steering elements are reactively tuned by varactor diodes in series with small inductors. The beam-control procedure was derived through the use of a genetic algorithm based on adjusting the required reactance values to obtain the optimum solution as indicated by the cost function. The GA was also initially used as an optimisation tool to derive the antenna design from its specification. Finally, reactive loading and time modulated switching techniques are applied to steer the beam of a circular uniformly spaced antenna array having a source element at its centre. Genetic algorithm (GA) and particle swarm optimisation (PSO) processes calculate the optimal values of reactances loading the parasitic elements, for which the gain can be optimised in a desired direction. For time modulated switching, GA and PSO also determine the optimal on and off times of the parasitic elements for which the difference in currents induced optimises the gain and steering of the beam in a desired direction. These methods were demonstrated by investigating a vertically polarised antenna configuration. A prototype antenna was constructed and experimental results compared with the simulations. Results showed that near optimal solutions for gain optimisation, sidelobe level reduction and beam steering are achievable by utilising these methods. In addition, a simple switching process is employed to steer the beam of a horizontally polarised circular antenna array. A time modulated switching process is applied through Genetic Algorithm optimisation. Several model examples illustrate the radiation beams and the switching time process of each element in the array.

Les travaux présentés dans ce mémoire de thèse portent sur la linéarisation large bande d'amplificateurs de puissance par prédistorsion analogique. Ce travail vise à réduire la pollution spectrale provoquée par leur comportement non-linéaire lors d'une transmission satellite. Ce travail de thèse débute par une présentation des amplificateurs de puissance utilisés dans les émetteurs, en exposant les conséquences de leur comportement non-linéaire sur la qualité du signal. Pour pallier à cela, les techniques de linéarisation couramment utilisées ont été recensées, en mettant l'accent sur leurs avantages et inconvénients. C'est sur la base de cet état de l'art qu'une structure de prédistorsion analogique a pu être identifiée. Il s'agit d'une structure en réflexion à base de diodes Schottky, dont une partie de ce mémoire est consacrée à l'analyse de leur comportement non-linéaire. Appuyée par des résultats de simulations et des mesures effectuées sur maquettes, cette analyse nous a conduit à la mise en œuvre de la structure en réflexion dans le cadre de la linéarisation d'un amplificateur à tube à onde progressive (ATOP) en bande Ku. Nos travaux se sont ensuite tournés vers une nouvelle structure plus innovante, basée sur la mise en cascade de deux circuits de prédistorsion. La structure proposée bénéficie d'une configuration plus flexible et plus précise que la précédente, ce qui nous a permis d'obtenir de meilleurs résultats en matière d'amélioration de la linéarité. La dernière partie de ce travail de thèse est dédiée à l'approche expérimentale de deux méthodes numériques de prédistorsion en bande de base. L'intérêt de cette approche repose sur l'évaluation expérimentale de l'amélioration possible de la linéarité de l'ATOP et la comparaison avec les résultats obtenus par prédistorsion analogique. / The research reported in this PhD Thesis is focused on power amplifier wideband linearization by analog predistortion. This work aims to reduce the spectral regrowth due to their nonlinear response over the satellite transmission. This dissertation starts with a presentation of power amplifiers used in transmitters. Through it, we expose their nonlinearity effects on the signal quality. To overcome those effects, the lattest linearization methods were reviewed, highlighting their strengths and weaknesses. Based on this state of art, an analog predistortion structure was identified. It relates to a reflective structure made up of Schottky diodes, of which a part of this thesis is devoted to the analysis of its nonlinear behavior. Drawn on simulations and measurements, this analysis led us to the implementation of the reflective structure for the purpose of a traveling wave tube amplifier linearization over the Ku band. Our work was then directed towards to a new more innovative structure built on two predistortion circuits wired in series. This new structure gets a more flexible and accurate configuration compared to the previous one and allowed us to obtain better results regarding linearity improvement. The last part of this thesis work is dedicated to an experimental approach of two base band digital predistortion methods. The aim of this approach rests on the achievable enhancement of TWTA linearity and the comparison between the results obtained with the analog predistortion.

Cette thèse a pour objectif de contribuer à la caractérisation et à la modélisation des transistors organiques en couches minces ou OTFTs (Organic Thin Film Transistors). Elle s’est déroulée en partenariat avec le CEA-LITEN qui dispose d'une technologie imprimée ayant démontré sa fonctionnalité à plusieurs reprises. Le but de ce travail est d'abord de comprendre le fonctionnement des transistors organiques afin de déterminer l'impact des paramètres technologiques sur les caractéristiques électriques. Ceci est fait en utilisant une approche par simulation grâce aux paramètres extraits à partir de la mesure. La dépendance en géométrie et en température des paramètres du transistor est observée et étudiée afin de proposer un modèle valide prenant en compte ces variations. Le modèle doit être intégrable dans les flots de conception classiques de la microélectronique (Cadence, Eldo, ADS, etc…). Des modèles de dispersion sont présentés et par la suite utilisés pour la simulation et la réalisation de circuits analogiques organiques. / This thesis focuses on a contribution of organic thin film transistors (OTFTs) characterization and modeling. It takes place in partnership with CEA-LITEN, which has a printed technology. This technology has demonstrated its functionality repeatedly. The goal is to first understand in depth the functioning of the organic transistors to determine the impact of technological parameters on electrical characteristics. This is done using a simulation approach using the parameters extracted from the measurements. The geometry and temperature dependences of the transistor parameters are observed and studied in order to provide a valid model for a wide range of geometry and temperature. The proposed model should respect the following constraints: an integrability in conventional design tools (Cadence, Eldo, ADS, etc...) and must also include a dispersion model. This model is subsequently used to produce blocks of analog circuits.

Lasers bombeados por diodo semicondutor emitindo em 1mm têm diversas aplicações. Para muitas destas aplicações é desejado um feixe laser com uma boa qualidade e alta potência. Um dos maiores problemas encontrado quando se utiliza altas potências de bombeamento é a forte lente térmica gerada no meio ativo. Neste trabalho estuda-se um laser de Nd:YVO4 bombeado transversalmente por diodo laser em regime contínuo. Este tipo de bombeamento possibilita aproveitar o alto coeficiente de absorção do cristal tornando possível a obtenção de altas eficiências. Duas configurações de ressonadores foram estudadas. A primeira com uma dobra em ângulo rasante na superfície de bombeamento do cristal e a segunda com duas dobras nesta mesma face. Um laser de 22 watts de potência de saída e eficiência angular de 74% foi obtido com a primeira configuração sob um bombeamento de 35 watts. A qualidade do modo era de M2 = 26 ´ 11, na horizontal e na vertical, respectivamente. Uma melhora significativa na qualidade do feixe foi demonstrada quando feita a segunda dobra dentro do cristal. Uma potência de 17 watts foi atingida com essa configuração com qualidade de feixe de M2 = 3,4 ´ 3,7, na horizontal e na vertical, respectivamente. / Within the existing variety of laser cavity geometries and gain materials there is one combination that is particularly interesting because of its reduced complexity and high efficiency: the edge-pumped slab-laser using grazing-incidence geometry and a gain media with a very high pump absorption cross-section. In this work we studied a diode side-pumped Nd:YVO4 cw laser. We describe a single and a multiple bounce laser configurations. We demonstrate 22 W of multimode output power for 35 watts of pump power with a single pass through the gain media. A high optical-to-optical conversion efficiency of 63% and a slope efficiency of 74% with a very compact and simple Nd:YVO4 cavity that uses joint stability zones was achieved. The beam quality was M2 = 26 ´ 11 in the horizontal and vertical direction, respectively. With a double pass configuration we achieved 17 watts with a better beam quality of M2 = 3,4 ´ 3,7, in the horizontal and vertical direction, respectively.

Cette thèse se place dans le cadre du projet Diamonix, qui vise à établir une filière diamant en France. La thèse porte sur des travaux de dimensionnement de protection périphérique, structure nécessaire au bon fonctionnement des composants d’électronique de puissance. Le développement de protections périphériques applicables aux diodes Schottky sur diamant monocristallin nécessite plusieurs étapes. Après un premier chapitre détaillant l’état de l’art de l’utilisation de diamant en électronique de puissance, nous nous attardons sur la conception de protection périphérique basée sur une plaque de champ à l’aide de divers diélectriques et ensuite à l’aide d’un matériau semi-résistif dans le chapitre 2. Ces simulations sont réalisées à l’aide du logiciel SENTAURUS TCAD. Le troisième chapitre essaie de répondre aux problèmes technologiques posés par le chapitre 2. Nous avons ainsi développé une nouvelle technique de gravure basée sur une succession d’étapes utilisant Ar/O2 puis CF4/O2. Puis, dans un deuxième temps, nous avons réalisé des capacités Métal/Diélectrique/Diamant afin de qualifier le comportement des diélectriques sur le matériau diamant. Leur comportement est problématique mais il s’agit à notre connaissance de la première étude poussée de capacités sur diamant. Le chapitre 4 revient sur la fabrication et la caractérisation de diodes Schottky protégées à l’aide de plaques de champ sur divers diélectriques, les résultats obtenus étant mitigés. Enfin, la conclusion revient sur les résultats importants de simulation, de gravure, de caractérisation des capacités et des diodes Schottky pour ensuite s’élargir et donner des perspectives de travail. / This thesis work is part of the Diamonix project, which is about forming a France-based supply and fabrication of diamond electronics devices. Work in this thesis is centered upon designing a peripheral junction protection suitable for diamond Schottky diodes, a vital structure for the right behavior of power electronics components. Such design on monocristalline diamond substrates needs several steps. After a first chapter dealing with diamond state of the art in power electronics, emphasis is brought upon the design of a field plate protection using several dielectric materials and a semi-resistive component in the second chapter. Those simulations are carried out using SENTAURUS TCAD software suite. The third chapter tries to answer any technological difficulties met in the second chapter. For instance, a new etching technique based upon a succession of steps has beeen developped. Then, Metal/Dielectric/Diamond capacitors were made to determine the electrical behavior of those dielectrics on diamond. Their behavior is problematic but it is to our knowledge the first time such devices are characterized in such extent. The fourth chapter deals with the processing and characterizing of diamond Schottky diodes protected using field plates on several dielectrics, which measurements results are a bit disappointing. Finally, the conclusion insists on the main results of the thesis and then opens up to a discussion over the perspectives of future works around diamond.

Parmi les nombreuses applications des sources laser, certaines nécessitent une propagation du faisceau dans l'atmosphère sur plusieurs kilomètres : télémétrie, désignation, ou encore imagerie active. Pour éviter tout risque oculaire tout en proposant de plus grandes portées, ces applications doivent faire appel à des sources laser émettant une longueur d'onde dans la gamme à sécurité oculaire autour d'un minimum local d'absorption de l'atmosphère (1550-1650 nm). De telles sources existent déjà commercialement, mais ne répondent pas aux exigences militaires de compacité, de consommation électrique, de performance et de fonctionnement sur une large gamme de température (-40°C/+60°C).Mes travaux de thèse tentent d'apporter une réponse à l'ensemble de ces exigences. Avec l'aide des partenaires industriels Fibercryst et Cilas, ils portent sur la réalisation de sources laser compactes et efficaces à fibre cristalline Er3+:YAG directement pompée par une diode laser pour des applications militaires.A l'aide d'un algorithme de simulation d'un laser Er3+:YAG déclenché passivement élaboré et affiné durant la thèse, plusieurs sources sont réalisées expérimentalement. L'étude autour des absorbants saturables pour le déclenchement passif a permis une amélioration notable des caractéristiques du faisceau.Ces recherches, dont les résultats peuvent déjà présenter un certain intérêt commercial, ouvrent la voie vers de nouvelles techniques et architectures autour des sources laser à cristaux dopés aux ions erbium pour la conception de futurs prototypes plus performants. / Among the several applications of laser sources, some requires kilometers range propagation in the atmosphere : telemetry, guidance system or active imagery. High pulse energy improves the range of the system, but may cause permanent blindness to an observer's eyes. Hence, these applications must use laser beam which wavelength are located in the eye-safe region, ideally at the local minimum of the atmosphere absorption (1550-1650 nm). Such laser sources are already commercially available, but are not suited for the demanding military needs : compacity, electrical consumption, performance and large operating temperature range (-40°C/+60°C).My work aims to develop a laser source filling these specifications. Thanks to the collaboration with the industrial partners Fibercryst and Cilas, it focuses on the design of a compact, efficient, directly diode-pumped Er3+:YAG single cristal fiber laser for military applications.With a homemade numerical simulation of a passively Q-switched Er3+:YAG laser source, many laser emitters are experimentally designed and compared. Further studies around saturable absorbers allowed sensible improvements of the output pulse energy.This work, whose results may already be commercially interesting, may lead to new technics and architectures of erbium doped solid-state laser for better prototypes.

Ce travail présente la mise en œuvre du test par faisceau laser TPA pour l’étude de la sensibilité au phénomène SEB dans les diodes schottky en carbure de silicium. Le contexte de l’étude est décrit par un état de l’art du SEB sur les MOSFETs et Diodes en Silicium et en carbure de silicium. Une étude technologique et structurelle des composants en SiC a permis de dégager les avantages du SiC par rapport au Si conventionnel et a permis d’analyser les dégâts causés par le faisceau TPA. L’utilisation du montage expérimental sur la plateforme ATLAS dédié spécifiquement au test de matériaux à grand gap a permis de mettre en place une méthodologie de test sur des diodes schottky en SiC. L’efficacité de cette méthodologie est prouvée par l’obtention de résultats expérimentaux très originaux. La susceptibilité au SEB induit par la technique laser TPA a été démontrée. Les mesures SOA ont permis d’évaluer la robustesse des diodes schottky SiC face aux événements singuliers. Une modélisation analytique a été menée afin de comprendre la cause du mécanisme du SEB et la localisation des défauts induits par le faisceau TPA. / This work presents the implementation of the TPA laser beam testing to study the SEB phenomenon in silicon carbide Schottky diodes. The context of the study is described by a state of the art of SEB on Si and SiC MOSFETs and Diodes. Technological and structural study of SiC components has identified the benefits of SiC compared to conventional Si and permits to analyze the damage caused by the TPA beam. Using the experimental setup of the ATLAS platform dedicated specifically to test large gap materials has set up a test methodology on SiC Schottky diodes. The effectiveness of this methodology is demonstrated by obtaining original experimental results. Susceptibility to SEB induced by TPA laser technique has been demonstrated. SOA measurements were used to assess the robustness of SiC Schottky diodes to single event effects.An analytical modeling was conducted to understand the cause of the SEB mechanism and the location of defects induced by the TPA beam.

Les nitrures d’éléments III, à savoir GaN, InN, AlN et leurs alliages, forment une famille de matériaux semi-conducteurs dont les propriétés sont particulièrement intéressantes pour la réalisation de diodes électroluminescentes (LEDs). Leur intérêt réside en particulier dans leur bande interdite qui est directe et qui couvre une large bande spectrale de l’infrarouge (0,65eV pour InN) à l’ultraviolet (6,2eV pour AlN). En raison de l’absence de substrats accordés en maille avec ces matériaux, les couches minces hétéroépitaxiées de nitrure sont généralement touchées par des problèmes de qualité cristalline. Grâce au phénomène de relaxation des contraintes en surface, les nanofils offrent une solution prometteuse pour résoudre ce problème. Ils combinent de nombreux autres avantages : en comparaison des couches minces, l’efficacité quantique interne des LEDs peut être améliorée (surface effective plus importante permettant de diminuer l’effet Auger à courant injecté identique, absence de champ de polarisation en utilisant les facettes non polaires des nanofils) et l’extraction des photons est facilitée par l’effet guide d’onde des nanofils. Cependant, une des difficultés est de parvenir à contrôler la synthèse de ces nano-objets pour garantir une homogénéité des propriétés structurales d’un fil à l’autre et au sein d’un même fil. Dans ce contexte, mon travail de thèse a consisté à étudier d’un point de vue expérimental et théorique l’impact des inhomogénéités structurales sur les propriétés optoélectroniques de dispositifs à nanofils de type LED. J’ai pu mettre en évidence et modéliser un effet de concentration du courant dans les régions riches en indium lorsque les courants injectés sont modérés. Pour de forts courants, le courant se concentre à proximité du contact sur la coquille dopée p. Théoriquement, j’ai montré que la dérive des porteurs de charge dans les puits quantiques et leur diffusion unipolaire et ambipolaire en présence d’un gradient de compositions des puits étaient négligeables. Par ailleurs, je me suis également intéressé à l’interprétation des caractéristiques courant-tension. A l’aide d’un modèle simple, j’ai également identifié la présence de courant de fuite par effet tunnel dans des structures présentant une densité importante de défaut. Dans une seconde partie de ma thèse, je me suis également intéressé à la caractérisation de nanofils à structure coeur-coquille par la technique de courant induit par faisceau d’électrons (Electron Beam Induced Current). La dépendance des cartographies EBIC en fonction de la tension appliquée et de l’énergie du faisceau incident a été modélisée. Ce travail m’a notamment amené à proposer une nouvelle méthode de caractérisation permettant de cartographier les résistivités du coeur et de la coquille des nanofils. / III-nitrides i.e. GaN, InN, AlN and their alloys are semiconductors of choice to fabricate optoelectronic devices such as Light Emitting Diodes (LEDs). One of their most interesting features relies in their direct band gap that covers a very wide spectral range, from infrared (0.65 eV for InN) to UV (6.2 eV for AlN). However, the lack of lattice-matched substrate has been responsible for strong crystalline quality issues in heteroepitaxial thin films. Thanks to stress relaxation at their surface, nanowires provide a smart solution to this problem. Besides, they have a few more assets. In comparison to thin films, nanowires can improve the internal quantum efficiency of LEDs because of their higher effective surface that leads to lowered current densities and thus mitigated Auger effect. The internal quantum efficiency also benefits from the possibility to grow the active region on non polar facets, thus getting rid of the detrimental high internal polarization-induced electric field in quantum wells. Furthermore, the photon extraction efficiency is enhanced by the guiding effect of nanowires. However, despite all this promising advantages, one of the main challenges remains the control of structural homogeneity from wire to wire but also inside single wires.In this context, my work has consisted into studying from an experimental and theoretical point of view the consequences of these structural inhomogeneities on the optoelectronic properties of nanowire based LED devices. I have shown that the current tends to gather into indium-rich regions for moderate bias. At higher bias, the dominant current path though the junction is generally located under the p-contact on the nanowire shell. I have theoretically demonstrated that the unipolar and ambipolar diffusion of carriers as well as their drift induced by a composition gradient inside the quantum wells is not significant in the devices I have studied. Moreover, I took also an interest in the detailed analyze of I-V curves. Thanks to a simple model, I have identified the presence of leakage current related to defect- and phonon-assisted tunneling effect. In the second part of my work, I have focused onto the characterization of core-shell wires using the Electron Beam Induced Current technique. The bias-dependant and acceleration voltage-dependant EBIC maps has been explained with a theoretical model based on equivalent circuits. This study leads me to suggest a new experimental method that can be used to map the nanowire core and shell resistivity.