Les propriétés électriques et mécaniques exceptionnelles du graphène font de ce matériau bidimensionnel à base de carbone, l’un des matériaux phare de la micro-électronique. L’objectif des ces travaux de recherche est de démontrer les possibilités nouvelles offertes par le graphène dans le domaine des transistors ultra-rapides et faible bruit. La fabrication de transistors RF a été réalisée sur des échantillons obtenus par graphitisation de substrat SiC. Ce travail s’est déroulé dans le cadre du projet ANR MIGRAQUEL, en partenariat avec le Laboratoire de Photonique et de Nanostructures (LPN), le Laboratoire Pierre Aigrain (LPA) de l’ENS, et l’Institut d’Electronique Fondamentale (IEF). Les couches de graphène utilisées dans cette thèse ont été synthétisées au LPN. Le développement et l’optimisation des différents procédés technologiques se sont déroulés en salle blanche. Les propriétés du matériau tels que la mobilité, la résistance par carré, ainsi que certaines caractéristiques technologiques comme les résistances de contact sont déduites de structures spécifiques. Ensuite, des caractérisations électriques en régime statique et dynamique effectuées sur des transistors graphène à effet de champ (GFET) ont été effectuées. Les meilleures performances hyperfréquence ont été obtenues sur des transistors à base de nano-rubans de graphène (GNRFET), avec une fréquence de coupure « intrinsèque » du gain en courant ft_intr=50GHz et une fréquence maximale d’oscillation fmax=29GHz; et ce pour une longueur de grille de Lg=75nm à Vds=300mV. / Outstanding electrical and mechanical properties of graphene make this two-dimensional carbon-based material, one of the leading microelectronics materials. The aim of this thesis is to demonstrate the new possibilities offered by graphene in the field of high-speed and low-noise transistors. RF transistors have been produced on samples obtained by graphitization of SiC substrates. This was possible through the ANR program MIGRAQUEL in partnership with the Laboratory of Photonics and Nanostructures (LPN), the Pierre Aigrain Laboratory (LPA) of ENS and the Institute of Fundamental Electronics (IEF). Graphene samples used in this thesis were synthesized in LPN. The development and optimization of the different technological steps process took place in clean-rooms. Material properties such as mobility, sheet resistance and some technological parameters such as contact resistance are made using specific samples. Then, each GFET and GNRFET (Graphene Nano-Ribbons FET) transistor were analyzed both in static and high-frequency regime. Finally, the best RF measurement in terms of intrinsisc current gain cut-off frequency and maximum oscillation frequency are respectively fr_intr=50GHz and fmax=29GHz; for a gate length of Lg=75nm at Vds=300mV.

L’électronique flexible est une thématique en plein essor, et impacte de nombreux secteurs applicatifs. L’objectif de cette thèse est de développer des composants sur substrats flexibles, pour des applications dans le domaine des radiofréquences. Elle est constituée de deux grandes parties : (i) la fabrication de composants passifs RF en utilisant la technologie d’impression par jet d’encre ; (ii) la fabrication de transistors graphène sur substrats flexibles. Ces travaux sont partiellement intégrés au projet Européen flagship GRAPHENE, et au projet ANR GRACY. La technique d’impression jet d’encre est particulièrement adaptée à la fabrication de composants sur substrats flexibles. L’un des challenges de cette approche technologique est de pouvoir atteindre une définition et une résolution adaptée au fonctionnement en régime radiofréquence. Le travail mené dans cette thèse a permis de réaliser des lignes homogènes de largeur minimale de 50 µm, et une résolution (distance entre 2 lignes de l’ordre de 15 µm. Différents composants passifs ont été fabriqués et caractérisés avec succès, et ce même en appliquant des contraintes en flexion aux dispositifs.Nous avons également développé et optimiser un procédé technologique, adapté à la fabrication de transistors à effet de champ à base de graphène (GFET), sur substrat flexible. Ce procédé présente un bilan thermique faible, et est basé sur l’utilisation d’une grille arrière à base d’aluminium dont l’oxyde naturel sert d’oxyde de grille. De nombreux transistors ont été fabriqués sur substrat kapton, et avec un bon rendement. Les meilleures performances en termes de fréquence de coupure du gain en courant (ft=39 GHz) et la fréquence maximale d’oscillation (fmax=13GHz) ont été mesurées sur un transistor de longueurs de grille Lg=100 nm et un développement de 12µm. Cette performance est à l’état de l’art de GFET flexibles. Ces performances sont conservées pour des contraintes atteignant 0,5%. / Flexible electronic has drawn growing attentions for past several years due to its largely potential applications. The objective of my PhD work is to develop devices based on flexible substrate, for RF applications. There are mainly two parts involved: (i) fabrication of passive devices (transmission lines, antenna, etc) using inkjet printing technology; (ii) fabrication of graphene field effect transistors on flexible substrate using graphene growth by CVD technique. This work is partially involved in the European Flagship program GRAPHENE, and the ANR program GRACY. Inkjet printing is a promising fabrication technology for flexible electronics. The challenge of this technology is the quality and reliability of printed patterns in terms of geometry. Based on optimized printing parameters, the structures of coplanar wave guide (CPW) transmission lines with nice printing quality were realized (definition of 50 µm, resolution down to 20 µm). The RF characterization of these transmission lines combining the considerations of geometric dimensions, sintering temperature, and substrate bending are presented. The outstanding electrical and mechanical properties make graphene suitable for flexible transistors. In this thesis, we have developed and optimized a new low temperature process based on back-gated structure either on rigid substrate than on flexible substrate (here kapton). From flexible transistors, we report as measured current gain cut-off frequency ( ft-DUT ,without any de-embedding) of 39 GHz and maximum oscillation frequency (fmax) of 13 GHz in devices with 100 nm gate length and 12 µm gate width. This result is at the level of the state of art for flexible GFETs.

Ce travail a été réalisé dans le cadre du projet GRACY regroupant l’IEMN et d’autres laboratoires de recherche : CALISTO et IMS Bordeaux. Ce manuscrit fait état d’une synthèse exhaustive des études et avancées menées dans le cadre de ce travail de thèse au sein de l’Institut d’Électronique, de Microélectronique et de Nanotechnologie (IEMN) dans le groupe CARBON. Le principal axe de réflexion de ce travail repose sur la conception, la modélisation et la caractérisation des dispositifs actifs et passifs sur substrat souples et rigides en vue du développement de nouveaux composants et de circuits électroniques avec des critères de performances de plus en plus importants. Au cours de ce travail, l’accent a été principalement portée sur les étapes essentielles à la réalisation de circuit intégré en ondes millimétriques utilisant la technologie coplanaire en impression jet d’encre et les transistors à effet de champ à base de graphène (GFETs). Ce mémoire montre en particulier l’intérêt et les potentialités du graphène pour son intégration au sein des circuits électroniques. De plus, une attention particulière a été portée sur la modélisation et les techniques de caractérisations relatives aux dispositifs passifs sur substrat souple. Par conséquent, un banc de caractérisation de ces éléments sur substrat flexibles a été développé au cours de cette thèse afin de vérifier et consolider expérimentalement leurs comportements. / This work was carried out under the project involving GRACY IEMN and other research laboratories: CALISTO and IMS Bordeaux. This manuscript reports a comprehensive overview of studies and advanced conducted as part of this thesis in the Institute of Electronics, Microelectronics and Nanotechnology (IEMN) in CARBON group. The main reflection axis of this work is based on the design, modeling and characterization of active and passive devices on flexible and rigid substrates for the development of new components and electronic circuits with increasingly important performance criteria. During this work, the focus was mainly focused on the essential steps to achieving integrated circuit millimeter wave using coplanar technology by inkjet printing and field effect transistors based on graphene (GFETs). This memory in particular shows the importance and potential of graphene for integration into electronic circuits. In addition, special attention was paid on modeling and characterization techniques related to passive devices on flexible substrates. Therefore, a characterization bench of these elements on flexible substrate has been developed during this thesis to verify and consolidate their behavior experimentally.

Recent advancements in photodetection using 2D materials suggest significant improvements in the performance of photodetectors. Among these, graphene field-effect transistors (GFETs) have demonstrated promising enhancements in photodetection, characterized by low noise, broad-spectrum response, high responsivity, and fast response [46, 126]. These photodetectors utilize graphene as the active channel, with graphene deposited on an insulating layer and semiconductor substrate. The contact of graphene with an insulator/semiconductor structure induces an interfacial potential to trap one type of photo-generated carrier at the interface. The trapped charge carriers induce opposite carriers in the graphene channel through the capacitive coupling effect. Due to a long lifetime of trapped carriers, the induced carriers in the graphene channel circulate multiple times under a given bias between the source and drain contacts, generating a photocurrent with high gain. Here, we explore GFET photodetectors fabricated on p-GaAs and p-Si wafers at room temperature. The photodetectors achieve a high gain. The photocurrent is generated due to the photogating effect. In this work, we explore GFET photodetectors fabricated on p-GaAs and p-Si wafers at room temperature. The photodetectors achieve a high gain and high responsivity of 106 (A/W) under the above bandgap excitation and can detect light below the bandgap illumination for both p-doped substrates. NEP and D* values of these detectors have been characterized along with response time characteristics. The NEP and D∗ values for both detectors are around 10−15 W/√ and 1012 Jones respectively, indicating a sensitive photodetection. The response time characterization suggests the rise and decay time depends on incident power. These results provide us with a deeper insight into the photodetection of the GFETs from the ultraviolet to near-infrared region. / Master of Science / Photodetectors have numerous applications in our daily lives, such as optical sensors in mobile phones, telecommunications, and biological imaging. However, current photodetection technologies often struggle to meet the increasing demands of modern equipment. These technologies require improving the existing photodetectors so that they can operate at exceptionally high speeds with low noise. Graphene is a highly sensitive material, that has shown significant potential for photodetection due to its fascinating optoelectronic and mechanical properties. In this study, we fabricated two field effect transistors on two semiconductor materials of different bandgaps with a single layer of graphene added on top of the substrate/insulator layer for photodetection. Specifically, we investigate the performance of GaAs and Si substrates to understand how varying the substrate can affect photodetection so that it can open up possible routes to future applications.

Field-effect transistors (FET) based on graphene as channel has extraordinaryproperties in terms of charge mobility, charge carrier density etc. However, there aremany challenges to graphene based FET due to the fact graphene is a monolayer ofatoms in 2-dimentional space that is strongly influenced by the operating conditions.One issue is that the Dirac point, or K-point, shifts to higher gate voltage whengraphene is exposed to atmosphere. In this study graphene field-effect transistors(GFET) based on commercially available CVD graphene are electrically characterizedthrough field effect gated measurements. The Dirac point is initially unobservable andlocated at higher gate voltages (>+42 V), indicating high p-doping in graphene.Different treatments are tried to enhance the properties of GFET devices, such astransconductance, mobility and a decrease of the Dirac point to lower voltages, thatincludes current annealing, vacuum annealing, hot plate annealing, ionized water bathand UV-ozone cleaning. Vacuum annealing and annealing on a hot plate affect thegated response; they might have decreased the overall p-doping, but also introducedDirac points and non-linear features. These are thought to be explained by localp-doping of the graphene under the electrodes. Thus the Dirac point of CVDgraphene is still at higher gate voltages. Finally, the charge carrier mobility decreasedin all treatments except current – and hot plate annealing, and it is also observed that charge carrier mobilities after fabrication are lower than the manufacturer estimatesfor raw graphene on SiO2/Si substrate.

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Moore's law has defined the semiconductor industry for the past 50 years. Devices continue to become smaller and increasingly integrated into the world around us. Beginning with personal computers, devices have become integrated into watches, phones, cars, clothing and tablets among other things. These devices have expanded in their functionality as well as their ability to communicate with each other through the internet. Further, devices have increasingly been required to have diverse of functionality. This combination of smaller devices coupled with diversification of device functionality has become known as more than Moore. In this thesis, more than Moore applications of graphene are explored in-depth. Graphene was discovered experimentally in 2004 and since then has fueled tremendous research into its various potential applications. Graphene is a desirable candidate for many applications because of its impressive electronic and mechanical properties. It is stronger than steel, the thinnest known material, and has high electrical conductivity and mobility. In this thesis, the potentials of graphene are examined for pressure sensors, humidity sensors and transistors. Through the course of this work, high sensitivity graphene pressure sensors are developed. These sensors are orders of magnitude more sensitive than competing technologies such as silicon nanowires and carbon nanotubes. Further, these devices are small and can be scaled aggressively. Research into these pressure sensors is then expanded to an exploration of graphene's gas sensing properties -- culminating in a comprehensive investigation of graphene-based humidity sensors. These sensors have rapid response and recovery times over a wide humidity range. Further, these devices can be integrated into CMOS processes back end of the line. In addition to CMOS Integration of these devices, a wafer scale fabrication process flow is established. Both humidity sensors and graphene-based transistors are successfully fabricated on wafer scale in a CMOS compatible process. This is an important step toward both industrialization of graphene as well as heterogeneous integration of graphene devices with diverse functionality. Furthermore, fabrication of graphene transistors on wafer scale provides a framework for the development of statistical analysis software tailored to graphene devices. In summary, graphene-based pressure sensors, humidity sensors, and transistors are developed for potential more than Moore applications. Further, a wafer scale fabrication process flow is established which can incorporate graphene devices into CMOS compatible process flows back end of the line. / <p>QC 20160610</p>