ANALYSE DES MECANISMES QUI REGISSENT LE FONCTIONNEMENT, STATISTIQUE ET DYNAMIQUE DU TRANSISTOR MOS A CANAL VERTICAL, QUI APPARTIENT A LA FAMILLE DES TRANSISTORS MOS DE PUISSANCE. ON DECRIT LES PRINCIPALES STRUCTURES MOS DE PUISSANCE REALISEES DANS LE MONDE, LEURS PARTICULARITES ET LEURS CARACTERISTIQUES ELECTRIQUES. EQUATIONS DE FONCTIONNEMENT DE CE TYPE DE TRANSISTOR EN REGIME STATIQUE, ET PROPOSITION D'UN MODELE DYNAMIQUE, BASE SUR LA THEORIE DES CHARGES SUR LES ELECTRODES. ETUDE THEORIQUE ET EXPERIMENTALE DES PPTES FREQUENTIELLES DU TRANSISTOR VMOS. CARACTERISATION D'UN AMPLIFICATEUR LARGE BANDE UTILISANT CE COMPOSANT

Despite the widespread interest in graphene electronics over the last decade, high-performance graphene field-effect transistors (GFETs) on flexible substrates have been rarely achieved, even though this atomic sheet is widely understood to have greater prospects for flexible electronic systems. In this work, we investigate the realization of high-performance graphene field effect transistors implemented on flexible plastic substrates. The optimum device structure for high-mobility and high-bendability is suggested with experimental comparison among diverse structures including top-gate GFETs (TG-GFETs), single/multi-finger embedded-gate GFETs with high-k dielectrics (EG-highk/GFETs), and embedded-gate GFETs with hexagonal boron nitride (h-BN) dielectrics. Flexible graphene transistors with high-k dielectric afforded intrinsic gain, maximum carrier mobility of 8,000 cm²/V·s, and importantly 32 GHz cut-off frequency. Mechanical studies reveal robust transistor performance under repeated bending down to 0.7 mm bending radius whose tensile strain corresponds to 8.6%. Passivation techniques, with robust mechanical and chemical protection in order to operate under harsh environments, for embedded-gate structures are also covered. The integration of functional coatings such as highly hydrophobic fluoropolymers combined with the self-passivation properties of the polyimide substrate provides water-resistant protection without compromising flexibility, which is an important advancement for the realization of future robust flexible systems based on graphene. / text

No description available.

This thesis is focused on the high-frequency performance of carbon nanotube field-effect transistors (CNFETs). Such transistors show their promising performance in the nanoscale regime where quantum mechanics dominates. The short-circuit, common-source, unity-current-gain frequency ft is analyzed through regional signal-delay theory. An energy-dependent effective-mass feature has been added to an existing SP solver and used to compare with results from a constant-effective-mass SP solver. At high drain bias, where electron energies considerably higher than the edge of the first conduction sub-band may be encountered, ft for CNFETs is significantly reduced with respect to predictions using a constant effective mass. The opinion that the band-structure-determined velocity limits the high-frequency performance has been reinforced by performing simulations for p-i-n and n-i-n CNFETs. This necessitated incorporating band-to-band tunneling into the SP solver. Finally, to help put the results from different CNFETs into perspective, a meaningful comparison between CNFETs with doped-contacts and metallic contacts has been made. Band-to-band tunneling, which is a characteristic feature of p-i-n CNFETs, can also occur in n-i-n CNFETs, and it reduces the ft dramatically.

This thesis presents a new simulation model for floating gate transistor (FGMOS) in nanometer scale technology where the transistors suffer from non-negligible gate leakage current due to the very thin Silicon oxide (SiO2) layer. The new FGMOS simulation model is used for transient and DC simulation and with any industry standard simulators such as Spector and various SPICE programs (i.e. HSPICE, WinSPICE, etc.). This model can be used for any technology that has SiO2 thickness less than 3nm and suffer from gate leakage current with no changes to the model itself; however, minimal changes need to be done to the gate tunnelling cell to comply with the technology parameters where the gate tunnelling current exponentially increases as tox decreases.

No description available.

<p>Recent advances in electromagnetics introduced tools that enable the creation of arti-</p><p>cial electromagnetic structures with exotic properties such as negative material pa-</p><p>rameters. The ability to express these parameters has experimentally demonstrated</p><p>using passive metamaterial structures. These structures, based on their passivity and</p><p>resonant properties, are typically associated with high loss and signicant bandwidth</p><p>limitations.</p><p>Enhancing and further exploring novel electromagnetic properties can be done</p><p>through embedding active circuits in the constitutive unit cells. Active elements</p><p>are able to supplement the passive inclusions to mitigate and overcome loss and</p><p>bandwidth limitations. The inclusion of these circuits also signcantly expands the</p><p>design space for the development of functional metamaterials and their potential</p><p>applications.</p><p>Due to the relative diculty of designing active circuits compared with passive</p><p>circuits, using active circuits in the construction of metamaterials is still an under-</p><p>developed area of research. By combining the two elds of active circuit design and</p><p>metamaterial design, we aim ll the functional active metamaterial design space.</p><p>This document provides the basis for understanding the design and synthesis of</p><p>functional active metamaterials.</p><p>To provide necessary background matter, chapter 1 will function as an introduc-</p><p>tion chapter, discussing how active electromagnetic metamaterials are created and characterized. There are also several required design techniques necessary to suc-</p><p>cessfully engineer a functional active metamaterial. The introduction will emphasize</p><p>on linking metamaterial unit cell response with RF/analog circuit design with a brief</p><p>introduction to the semiconductor physics important to aid in the understanding of</p><p>the full active metamaterial design and fabrication process.</p><p>The subsequent chapters detail our specic contributions to the eld of func-</p><p>tional active RF metamaterials. Chapter 2 introduces and characterizes a meta-</p><p>material designed to have a tunable quality factor (tunable resonant bandwidth).</p><p>This metamaterial is essentially passive but demonstrates the transistor's versatility</p><p>as a combination of tunable elements, motivating the use of embedding transistors</p><p>in metamaterials. After establishing a simple application of a transistor in a pas-</p><p>sive metamaterial, chapter 3 outlines the design and characterization of an active</p><p>metamaterial exhibiting the properties of loss cancellation and gain. Chapter 4 in-</p><p>troduces another active metamaterial with the ability to self-adapt to an incident</p><p>signal. Within the self-adapting system, several complex RF circuit systems are</p><p>simulatenously developed and implemented such as a self-oscillating mixer and a</p><p>phase locked loop. Conclusions and additional suggested future research directions</p><p>are discussed in chapter 5.</p><p>There are also several appendices attached at the end of this document that are</p><p>meant to assist future graduate students and other readers. The additional topics</p><p>include the experimental verication of a passive magnetic metamaterial acting as a</p><p>near eld parasitic, the stabilization and measurement of a tunnel diode, a discussion</p><p>on the challenges of realizing active inductors from discrete components, and a basic</p><p>strategy for creating a non-volatile metamaterial. It is my aim for these appendices</p><p>to help provide additional inspiration for future studies within the eld.</p> / Dissertation

The integration of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with plastic substrates enables emerging technologies such as flexible organic light emitting diode (OLED) displays. Current a-Si fabrication processes, however, create residual thin film stress that affects the underlying flexible substrate due to its high mismatch in the coefficient of thermal expansion resulting in a dimensional instability for fabricating TFTs on large area flexible substrates. The motivation of this thesis is to reduce this non-uniformity and improve fabrication throughput of bottom-gated inverted-staggered a-Si:H TFTs on flexible substrates. This thesis therefore encompasses the study of overlay misalignment on TFTs over 3 inch flexible substrates and investigates the electrical characteristics of the TFTs fabricated on plastic platforms. To reduce overlay misalignment of TFTs fabricated on flexible substrates, a plastic-on-carrier lamination process has been developed. The technique comprises of a polyimide tape to attach a 125 um-thick poly-ethylene-napthalate (PEN) flexible substrate to a rigid carrier. This process has been used to minimize stress induced strain of the PEN substrate during the fabrication process; strain, which has been observed after processing a-Si:H TFTs on free-standing substrates. This technique would in turn assist in fabricating uniform stacked-layers as required for a-Si:H TFT fabrication on the PEN substrates. Overlay misalignment is measured after each of the 5 consecutive lithographic steps at 4 corner-most edges of the PEN substrates using a standard optical microscope. Results have shown an overlay misalignment reduction from 21 um to 2 um on average based on the TFTs fabricated on free-standing flexible substrates while ensuring a centre alignment accuracy of +/- 0.5 um. Post fabrication adhesive removal to separate the PEN substrate from the rigid carrier has been accomplished by sample immersion in acetone. The results present a significant increase in fabrication throughput by reducing lithographic overlay misalignment such that the resolution of large-area flexible electronics would be enhanced. Electrical characteristics show the average performance of a-Si:H TFTs with an ON/OFF current ratio of 10^8, field effect mobility of ~0.8 cm^2/Vs, and gate leakage current of 10^-13 A.

Organic semiconductors are envisioned to have widespread applications in flexible displays, radio-frequency identification (RFID) tags, bio- and chem-sensors, as well as organic solar cells. Polymer semiconductors are particularly suitable for the low-cost manufacture of organic electronics using printing techniques due to their excellent solution processability and mechanical properties. This work focuses on the development of two novel building blocks, IBDF and DTA, which can be used for the construction of high performance organic thin film transistors (OTFTs) and organic photovoltaics (OPVs). Two copolymers, P6-IBDF-T and P5-IBDF-T, and a homopolymer P6-IBDF were prepared using the IBDF building block. Copolymer P6-IBDF-T has been prepared via the Stille-coupling polymerization. This polymer exhibits a small band gap of 1.36 eV with HOMO/LUMO energy level of -5.69 eV/-4.43 eV. P6-IBDF-T showed stable electron transport performance in encapsulated thin film transistors and ambipolar transport performance in non-encapsulated TFTs. Balanced hole/electron mobilities of up to 8.2 ??10-3/1.0 ??10-2 cm2V-1s-1 was achieved in bottom-contact, bottom-gate organic thin film transistors. In addition, the broad absorption of the polymer over the UV-Vis range suggested that this polymer is suitable for applications in solar cells. The effect of conjugation on mobility and UV-vis spectra of the polymer was studied by comparing P5-IBDF-T with P6-IBDF-T. The ideal of indirect electron transition was proposed to explain the difference between UV-Vis light absorption spectra for these two polymers. DTA building block was used to construct four D-A copolymers, namely PDTA-T, PDTA-BT, PDAT-BTV, and PDTA-TT. These polymers were characterized by UV-Vis, CV, DSC, TGA, AFM and XRD. Device performance was also investigated on OTFTs. The device performance of DTA based polymer increased as the area of electron donor increase from T in PDTA-T to BTV in PDTA-BTV. PDTA-BTV exhibits hole mobility of 1.3??10-3 cm2 V-1 s-1 with Ion/Ioff value of ~103-4 in bottom-contact, bottom-gate organic thin film transistors. All DTA based copolymers exhibited small optical bandgaps (1.18 ??? 1.27 eV) and required none or moderate thermal treatment during fabrication process. These make them promising candidates for cost-effective OPV applications.

The use of silicon carbide (SiC) as a base material in power electronics has manyadvantages, including high breakdown voltage and excellent temperature endurance.However, the packaging of such electronics presents major challenges and there is aneed for packaging that can operate in higher temperature. The purpose of this thesishas been to develop a test method and verify the functionality of SiC powertransistors prototypes with a new packaging technique developed by Swerea IVF AB.It includes setting up an electrical test-bed for power and high temperature cyclingand analysis of the results. Even though test confirmed functionality after thepackaging process, (at room temperature) the performance seemed to have been reduced. This could be a result of the measurement setup and the packaging process.In higher temperature the transistors failed to operate longer than a couple ofminutes which showed the weaknesses in the design and the challenges with this typeof packaging.