In the last 25 years, organic or "plastic" solar cells have gained commercial interest as a light-weight, flexible, colorful, and potentially low-cost technology for direct solar energy conversion into electrical power. Currently, organic solar cells with a maximum power conversion effciency (PCE) of 12% can compete with classical silicon technology under certain conditions. In particular, a variety of strongly absorbing organic molecules is available, enabling custom-built organic solar cells for versatile applications. In order to improve the PCE, the charge carrier mobility in organic thin films must be improved. The transport characterization of the relevant materials is usually done in neat layers for simplicity. However, the active layer of highly efficient organic solar cells comprises a bulk heterojunction (BHJ) of a donor and an acceptor component necessary for effective charge carrier generation from photo-generated excitons. In the literature, the transport properties of such blend layers are hardly studied. In this work, the transport properties of typical BHJ layers are investigated using space-charge limited currents (SCLC), conductivity, impedance spectroscopy (IS), and thermally stimulated currents (TSC) in order to model the transport with numerical drift-diffusion simulations. Firstly, the influence of an exponential density of trap states on the thickness dependence of SCLCs in devices with Ohmic injection contacts is investigated by simulations. Then, the results are applied to SCLC and conductivity measurements of electron- and hole-only devices of ZnPc:C60 at different mixing ratios. Particularly, the field and charge carrier density dependence of the mobility is evaluated, suggesting that the hole transport is dominated by exponential tail states acting as trapping sites. For comparison, transport in DCV5T-Me33:C60, which shows better PCEs in solar cells, is shown not to be dominated by traps. Furthermore, a temperature-dependent IS analysis of weakly p-doped ZnPc:C60 (1:1) blend reveals the energy-resolved distribution of occupied states, containing a Gaussian trap state as well as exponential tail states. The obtained results can be considered a basis for the characterization of trap states in organic solar cells. Moreover, the precise knowledge of the transport-relevant trap states is shown to facilitate modeling of complete devices, constituting a basis for predictive simulations of optimized device structures.:1 Introduction 2 Organic Semiconductors and Solar Cells 2.1 Structural, Optical, and Energetic Properties 2.2 Charge Carrier Transport 2.2.1 Classical Transport Models 2.2.2 Hopping and Tunneling Transport 2.2.3 Limitations of Transport Characterization 2.3 Doping 2.4 Single Carrier Devices 2.4.1 Theory of Space-Charge Limited Currents 2.4.2 Electrical Potential Mapping by Thickness Variation 2.4.3 Influence of the Contacts 2.5 Organic Solar Cells 2.5.1 Principles 2.5.2 The p-i-n Concept 2.5.3 Recombination 2.5.4 Electrical Characterization 3 Numerical Drift-Diffusion Simulations 3.1 Modeling Organic Semiconductors 3.2 System of Differential Equations 3.3 Simulation Algorithm and Modules 4 Exploiting Contact Diffusion Currents for Trap Characterization in Organic Semiconductors 4.1 Motivation 4.2 Drift-Diffusion Model 4.3 Results and Discussion 4.4 Conclusion 5 Transport Characterization of Donor-Acceptor Blend Layers 5.1 Motivation 5.2 Device Fabrication 5.3 Hole Transport in ZnPc:C60 Blends with Balanced Mixing Ratios 5.3.1 Current-Voltage Measurements 5.3.2 Drift-Diffusion Model 5.3.3 Modeling Results 5.3.4 Discussion 5.4 Hole Transport in Fullerene-Rich ZnPc:C60 Blends 5.4.1 Results and Discussion 5.5 Electron Transport in ZnPc:C60 (1:1) 5.5.1 Results and Discussion 5.6 Transport in Blend Layers with the High Efficiency Donor DCV2-5T-Me33 5.6.1 Hole Transport in DCV2-5T-Me33:C60 5.6.2 Electron Transport in DCV2-5T-Me33:C60 5.7 Conclusions for Transport in Blend Layers 6 Doping-Enabled Density of States Determination in Donor-Acceptor Blend Layers 6.1 Motivation 6.2 Theory 6.3 Methods 6.4 Results 6.4.1 Impedance Spectroscopy 6.4.2 Fermi level, Mott-Schottky Analysis, and Band Diagram 6.4.3 DOOS Determination 6.4.4 Thermally Stimulated Currents 6.4.5 Solar Cell Characteristics 6.5 Discussion 6.6 Conclusions on the DOS of ZnPc:C60 (1:1) 7 Conclusion and Outlook Materials, Symbols, Abbreviations Bibliography / Organische oder "Plastik"-Solarzellen haben in den letzten 25 Jahren eine rasante Entwicklung durchlaufen. Kommerziell sind sie vor allem wegen ihres geringen Gewichts, Biegsamkeit, Farbigkeit und potentiell geringen Herstellungskosten interessant, was zukünftig auf spezielle Anwendungen zugeschnittene Solarzellen ermöglichen wird. Die Leistungseffzienz von 12% ist dabei unter günstigen Bedingungen bereits mit klassischer Siliziumtechnologie konkurrenzfähig. Um die Effzienz weiter zu steigern und damit die Wirtschaftlichkeit zu erhöhen, muss vor allem die Ladungsträgerbeweglichkeit verbessert werden. In organischen Solarzellen werden typischerweise Donator-Akzeptor-Mischschichten verwendet, die für die effziente Generation freier Ladungsträger aus photo-induzierten Exzitonen verantwortlich sind. Obwohl solche Mischschichten typisch für organische Solarzellen sind, werden Transportuntersuchungen der relevanten Materialien der Einfachheit halber meist in ungemischten Schichten durchgeführt. In der vorliegenden Arbeit wird der Ladungstransport in Donator-Akzeptor-Mischschichten mithilfe raumladungsbegrenzter Ströme (space-charge limited currents, SCLCs), Leitfähigkeit, Impedanzspektroskopie (IS) und thermisch-generierter Ströme (thermally stimulated currents, TSC) untersucht und mit numerischen Drift-Diffusions-Simulationen modelliert. Zunächst wird mittels Simulation der Einfluss exponentiell verteilter Fallenzustände auf das schichtdickenabhängige SCLC-Verhalten unipolarer Bauelemente mit Ohmschen Kontakten untersucht. Die Erkenntnisse werden dann auf Elektronen- und Lochtransport in ZnPc:C60-Mischschichten mit verschiedenen Mischverhältnissen angewendet. Dabei wird die Beweglichkeit als Funktion von elektrischem Feld und Ladungsträgerdichte dargestellt, um SCLC- und Leitfähigkeitsmessungen zu erklären, was mit einer exponentiellen Fallenverteilung gelingt. Zum Vergleich werden dieselben Untersuchungen in DCV2-5T-Me33:C60, dem effizientesten der bekannten Solarzellenmaterialien dieser Art, wiederholt, ohne Anzeichen für fallendominierten Transport. Des weiteren werden erstmals schwach p-dotierte ZnPc:C60-Mischschichten mit temperaturabhängiger IS untersucht, um direkt die Dichte besetzter Lochfallenzustände zu bestimmen. Dabei werden wiederum exponentielle Fallenzustände sowie eine Gaußförmige Falle beobachtet. Insgesamt tragen die über Fallenzustände in Mischschichten gewonnenen Erkenntnisse zum Verständnis von Transportprozessen bei und bilden damit eine Grundlage für die systematische Identifizierung von Fallenzuständen in Solarzellen. Außerdem wird gezeigt, dass die genaue Beschreibung der transportrelevanten Fallenzustände die Modellierung von Bauelementen ermöglicht, auf deren Grundlage zukünftig optimierte Probenstrukturen vorhergesagt werden können.:1 Introduction 2 Organic Semiconductors and Solar Cells 2.1 Structural, Optical, and Energetic Properties 2.2 Charge Carrier Transport 2.2.1 Classical Transport Models 2.2.2 Hopping and Tunneling Transport 2.2.3 Limitations of Transport Characterization 2.3 Doping 2.4 Single Carrier Devices 2.4.1 Theory of Space-Charge Limited Currents 2.4.2 Electrical Potential Mapping by Thickness Variation 2.4.3 Influence of the Contacts 2.5 Organic Solar Cells 2.5.1 Principles 2.5.2 The p-i-n Concept 2.5.3 Recombination 2.5.4 Electrical Characterization 3 Numerical Drift-Diffusion Simulations 3.1 Modeling Organic Semiconductors 3.2 System of Differential Equations 3.3 Simulation Algorithm and Modules 4 Exploiting Contact Diffusion Currents for Trap Characterization in Organic Semiconductors 4.1 Motivation 4.2 Drift-Diffusion Model 4.3 Results and Discussion 4.4 Conclusion 5 Transport Characterization of Donor-Acceptor Blend Layers 5.1 Motivation 5.2 Device Fabrication 5.3 Hole Transport in ZnPc:C60 Blends with Balanced Mixing Ratios 5.3.1 Current-Voltage Measurements 5.3.2 Drift-Diffusion Model 5.3.3 Modeling Results 5.3.4 Discussion 5.4 Hole Transport in Fullerene-Rich ZnPc:C60 Blends 5.4.1 Results and Discussion 5.5 Electron Transport in ZnPc:C60 (1:1) 5.5.1 Results and Discussion 5.6 Transport in Blend Layers with the High Efficiency Donor DCV2-5T-Me33 5.6.1 Hole Transport in DCV2-5T-Me33:C60 5.6.2 Electron Transport in DCV2-5T-Me33:C60 5.7 Conclusions for Transport in Blend Layers 6 Doping-Enabled Density of States Determination in Donor-Acceptor Blend Layers 6.1 Motivation 6.2 Theory 6.3 Methods 6.4 Results 6.4.1 Impedance Spectroscopy 6.4.2 Fermi level, Mott-Schottky Analysis, and Band Diagram 6.4.3 DOOS Determination 6.4.4 Thermally Stimulated Currents 6.4.5 Solar Cell Characteristics 6.5 Discussion 6.6 Conclusions on the DOS of ZnPc:C60 (1:1) 7 Conclusion and Outlook Materials, Symbols, Abbreviations Bibliography

I) Introduction p-Conjugated polymers inherently combine electronic properties of inorganic semiconductor crystals and material characteristics of organic plastics due to their special molecular design. This unique combination has led to developing new unconventional optoelectronic technologies and, further, resulted in the evolution of semiconducting polymers (SCPs) as fundamental components for novel electronic devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) and organic solar cells (OSCs).[1–5] Moreover, the material flexibility, capability for thin-film formation, and solution processibility additionally allow utilizing modern printing technologies for the large-scale fabrication of flexible, light-weight organic electronics. This especially enables to significantly increase the production speed and, moreover, to drastically reduce the costs per unit.[6, 7] In particular, transistors are the most important elements in modern functional electronic devices because of acting as electronic switches in logic circuits or in displays to control pixels. However, due to molecular arrangement and interactions, the electronic performance of SCPs cannot compete with the one of monocrystalline silicon which is used in state-of-the-art high-performance microtechnology.[5, 8] Nonetheless, intensive and continuing efforts of scientists focused on improving the performance of OFETs, with the special focus on the charge carrier mobility, by optimizing the polymer structure, processing conditions and OFET device architecture. By this, it was possible to identify crucial relationships between polymer structure, optoelectronic properties, microstructure, and OFET performance.[8] Nowadays, the interdisciplinary scientific success is represented by high-performance SCPs with charge carrier mobilities exceeding the value of amorphous silicon.[3, 9] However, further research is essential to enable developing the next generation of electronic devices for application in healthcare, safety technology, transportation, and communication. II) Objective and Results Within the scope of this doctoral thesis, current high-performance p-conjugated SCPs should be studied comprehensively to improve the present understanding about the interdependency between molecular structure, material properties and charge transport. Therefore, the extensive research approaches focused on different key aspects of high charge carrier mobility polymers for organic transistors. The performed investigations comprised the impact of, first, novel design concepts, second, precise structural modifications and, third, synthetic and processing conditions and led to the major findings listed below. 1. The design concept of tuning the p-conjugation length allows to gradually modulate physical material properties and demonstrates that a strong localization of frontier molecular orbitals in combination with a high degree of thin-film ordering can provide a favorable platform for charge transport in p-conjugated semiconducting polymers.[1] 2. The replacement of thiophene units with thiazoles in naphthalene diimide-based p- conjugated polymers allows to increase interchain interactions and to lower frontier molecular orbitals. This compensates the potentially detrimental enhancement of backbone torsion and drives the charge transport to unipolar electron transport, whereas mobility values are partially comparable with those of the respective thiophene containing analogs. 3. p-Conjugated diketopyrrolo[3,4-c]pyrrole-based copolymers can be synthesized within fifteen minutes what, in combination with avoiding aqueous washings and optimizing processing conditions, allowed an increase in morphological and energetic order and, thus, improved the charge transport properties significantly. III) Conclusion The key findings of this doctoral thesis provide new significant insights into important aspects of designing, synthesizing and processing high charge carrier mobility polymers. By this, they can guide future research to further improve the performance of organic electronic devices - decisive for driving the development and fabrication of smart, functional and wearable next-generation electronics. References [1] T. Erdmann, S. Fabiano, B. Milián-Medina, D. Hanifi, Z. Chen, M. Berggren, J. Gierschner, A. Salleo, A. Kiriy, B. Voit, A. Facchetti, Advanced Materials 2016, 28 (41), 9169–9174, DOI:10.1002/adma.201602923. [2] Y. Karpov, T. Erdmann, I. Raguzin, M. Al-Hussein, M. Binner, U. Lappan, M. Stamm, K. L. Gerasimov, T. Beryozkina, V. Bakulev, D. V. Anokhin, D. A. Ivanov, F. Günther, S. Gemming, G. Seifert, B. Voit, R. Di Pietro, A. Kiriy, Advanced Materials 2016, 28 (28), 6003–6010, DOI:10.1002/adma.201506295. [3] A. Facchetti, Chemistry of Materials 2011, 23 (3), 733–758, DOI:10.1021/cm102419z. [4] A. J. Heeger, Chemical Society Reviews 2010, 39, 2354–2371, DOI:10.1039/B914956M. [5] H. Klauk, Chemical Society Reviews 2010, 39, 2643–2666, DOI:10.1039/B909902F. [6] S. G. Bucella, A. Luzio, E. Gann, L. Thomsen, C. R. McNeill, G. Pace, A. Perinot, Z. Chen, A. Facchetti, M. Caironi, Nature Communications 2015, 6, 8394, DOI:10.1038/ncomms9394. [7] H. Sirringhaus, T. Kawase, R. H. Friend, T. Shimoda, M. Inbasekaran, W. Wu, E. P. Woo, Science 2000, 290 (5499), 2123–2126, DOI:10.1126/science.290.5499.2123. [8] D. Venkateshvaran, M. Nikolka, A. Sadhanala, V. Lemaur, M. Zelazny, M. Kepa, M. Hurhangee, A. J. Kronemeijer, V. Pecunia, I. Nasrallah, I. Romanov, K. Broch, I. McCulloch, D. Emin, Y. Olivier, J. Cornil, D. Beljonne, H. Sirringhaus, Nature 2014, 515 (7527), 384–388, DOI:10.1038/nature13854. [9] S. Holliday, J. E. Donaghey, I. McCulloch, Chemistry of Materials 2014, 26 (1), 647–663, DOI: 10.1021/cm402421p.

As modern microelectronics advances, enormous challenges have to be overcome in order to further increase device performance, enabling highspeed and ultra-low-power applications. With progressive scaling of Silicon MOSFETs, charge carrier mobility has dropped significantly and became a critical device parameter over the last decade. Present technology nodes make use of strain engineering to partially recover this mobility loss. Even though carrier mobility is a crucial parameter for present technology nodes, it cannot be determined accurately by methods typically available in industrial environments. A major objective of this work is to study the magnetoresistance mobility μMR of strained VLSI devices based on a 28 nm ground rule. This technique allows for a more direct access to charge carrier mobility, compared to conventional current/ voltage and capacitance/ voltage mobility derivation methods like the effective mobility μeff, in which series resistance, inversion charge density and effective channel length are necessary to extract the mobility values of the short channel devices. Aside from providing an anchor for accurate μeff measurements in linear operation conditions, μMR opens the possibility to investigate the saturation region of the device, which cannot be accessed by μeff. Electron and hole mobility of nFET and pFET devices with various gate lengths are studied from linear to saturation region. In addition, the interplay between mobility enhancement due to strain improvement, and mobility degradation due to short channel effects with decreasing channel length is analyzed. As a concept device for future nanoelectronic building blocks, silicon nanowire Schottky field-effect transistors are investigated in the second part of this work. These devices exhibit an ambipolar behaviour, which gives the opportunity to measure both electron and hole transport on a single device. The temperature dependence of the source/drain current for specific gate and drain voltages is analyzed within the framework of voltage dependent effective barrier heights.:1. Einleitung 2. Theoretische Grundlagen 3. Charakterisierungsmethoden 4. Messaufbau 5. Ergebnisse der Untersuchungen an MOSFETs 6. Ergebnisse der Untersuchungen an SiNW Transistoren 7. Zusammenfassung Anhang Danksagungen

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No description available.

Les semi-conducteurs organiques à base d’aluminium ont été systématiquement synthétisés et caractérisés par méthodes photo-physiques et électrochimiques. Une étude de leur relation structure-propriétés électroniques a été menée. Les orbitales frontières ont été comparées à celles obtenues par calcul. De nouvelles méthodes ont été utilisées permettant une description de la morphologie des SCOs et un calcul de mobilité des porteurs de charges associés. La mobilité des trous dans Al(Op)3 a été mesurée sur des transistors en film minces: 0.6-2.1×10−6cm2V−1s−1. Par des techniques de spectroscopie en photoémission, la surface de l’hybride Co/Al(Op)3 a été sondée, révélant deux états d’interfaces hybrides, où la polarisation de spin de HIS1 est 8% plus élevée comparée au cobalt nu, et 4% plus faible dans HIS2. Enfin, des aimant moléculaires à base de phénalényle ont été étudiés. [Dy(Op)2Cl(HOp)(EtOH)] présente notamment un gap énergétique de 43.8K et un temps de relaxation de 5x10-4 s. / Aluminum-based organic semiconductors (OSCs) were systematically synthesized and studied by photophysical and electrochemical methods to identify a relationship between their chemical structure and electronic properties, using Alq3 as benchmark. Experimental HOMO and LUMO were compared to those computed. In addition, newly developed methods were implemented to generate morphologies and calculate charge carrier mobilities. The hole mobility of Al(Op)3 was measured in thin film transistors: 0.6-2.1×10−6 cm2V−1s−1. By photoemission spectroscopy techniques, the Co/Al(Op)3 hybrid interface was probed. Two hybrid interface states (HISs) were unraveled; the SP (spin polarization) of HIS1 is 8% higher than bare cobalt, whereas the SP of HIS2 is 4% lowered. At last, phenalenyl-based dysprosium SMMs (single-molecule magnet) were investigated. [Dy(Op)2Cl(HOp)(EtOH)] showed an energy gap of 43.8K and a quantum relaxation time of 5x10-4s.

L’accroissement du champ d’application et de la performance des microcontrôleurs s’accompagne d’une augmentation de la puissance consommée limitant l’autonomie des systèmes nomades (smartphones, tablettes, ordinateurs portables, implants biomédicaux, …). L’étude menée dans le cadre de la thèse, consiste à réduire la consommation dynamique des circuits fabriqués en technologie CMOS 80 nm avec mémoire non-volatile embarquée (e-NVM) ; à travers l’amélioration des performances des transistors MOS. Pour augmenter la mobilité des porteurs de charge, des techniques de fabrication utilisées dans les nœuds les plus avancés (40 nm, 32 nm) sont d’abord étudiées en fonction de différents critères (intégration, coût, gain en courant/performance). Celles sélectionnées sont ensuite optimisées et adaptées pour être embarquées sur une plate-forme e-NVM 80 nm. L’étape suivante est d’étudier comment transformer le gain en courant, en gain sur la consommation dynamique, sans dégrader la consommation statique. Les approches utilisées ont été de réduire la tension d’alimentation et la largeur des transistors. Un gain en consommation dynamique supérieur à 20 % est démontré sur des oscillateurs en anneau et sur un circuit numérique conçu avec près de 20 000 cellules logiques. La méthodologie appliquée sur le circuit a permis de réduire automatiquement la taille des transistors (évitant ainsi une étape de conception supplémentaire). Enfin, une dernière étude consiste à optimiser la consommation, les performances et la surface des cellules logiques à travers des améliorations de conception et une solution permettant de réduire l’impact de la contrainte induite par l’oxyde STI. / The increase of the scope of application and the performance of microcontrollers is accompanied by an increase in power consumption reducing the life-time of mobile systems (smartphones, tablets, laptops, biomedical implants, …). Here, the work consists of reducing the dynamic consumption of circuits manufactured in embedded non-volatile memories (e-NVM) CMOS 80 nm technology by improving the performance of MOS transistors. In order to increase the carriers’ mobility, manufacturing techniques used in the most advanced technological nodes (40 nm, 32 nm) are firstly studied according to different criteria (process integration, cost, current/performance gain). Then, selected techniques are optimized and adapted to be used on an e-NVM technological platform. The next step is to study how to transform the current gain into dynamic power gain without impacting the static consumption. To do so, the supply voltage and the transistor widths are reduced. Up to 20 % in dynamic current gain is demonstrated using ring oscillators and a digital circuit designed with 20,000 standard cells. The methodology applied on the circuit allows automatic reduction to all transistor widths without additional design modifications. Finally, a last study is performed in order to optimize the consumption, the performance and the area of digital standard cells through design improvements and by reducing the mechanical stress of STI oxide.

After the experimental discovery of graphene at the beginning of the 21st century, many other interesting 2D materials have been discovered. However, the electrical and optical properties of these layers are greatly influenced by the composition and quality of the surrounding materials. In order to preserve the exceptional properties of thin films, attention has gradually been drawn to heterostructures from 2D composite materials. This thesis describes the preparation and characterization of heterostructures composed of graphene and hexagonal boron nitride. In addition, a specific focus will be placed on optimizing the production process of heterostructures by the dry thin film transfer process, prepared by micromechanical exfoliation. Characterization and quality of prepared layers are controlled by Raman spectroscopy, while morphology is examined by atomic force microscope (AFM). Furthermore, the electrical properties of the graphene-hBN device are discussed and the charge carrier of the graphene field-effect transistor is measured.

Mit dem Erreichen der Grenzen der konventionellen MOSFET-Skalierung werden neue Techniken untersucht, um die Leistungsfähigkeit der CMOS-Technologie dem bisherigen Trend folgend weiter zu steigern. Einer dieser Ansätze ist die Verwendung mechanischer Verspannungen im Transistorkanal. Mechanische Verspannungen führen zu Kristalldeformationen und ändern die elektronische Bandstruktur von Silizium, so dass n- und p-MOSFETs mit verspannten Kanälen erhöhte Ladungsträgerbeweglichkeiten und demzufolge eine gesteigerte Leistungsfähigkeit aufweisen. Die vorliegende Arbeit beschäftigt sich mit den Auswirkungen mechanischer Verspannungen auf die elektronischen Eigenschaften planarer Silicon-On-Insulator-MOSFETs für Höchstleistungsanwendungen sowie mit deren Optimierung und technologischen Begrenzungen. Der Effekt der Verspannung auf die Bandstruktur von Silizium und die Ladungsträgerbeweglichkeit wird zunächst systematisch mit Hilfe der empirischen Pseudopotenzialmethode und der Deformationspotenzialtheorie untersucht. Verringerte Streuraten und kleinere effektive Massen als Folge der Aufspaltung der Energiebänder sowie von Bandverformungen sind der Hauptgrund für eine erhöhte Löcher- bzw. Elektronenbeweglichkeit. Die unterschiedlichen Konzepte zur Erzeugung der Verspannung werden kurz rekapituliert. Der Schwerpunkt der Untersuchungen liegt auf den verspannten Deckschichten, den Si1-xGex- bzw. Si1-yCy- Source/Drain-Gebieten, den verspannungsspeichernden Prozessen und den verspannten Substraten. Die starke Abhängigkeit dieser Verspannungstechniken von der Transistorstruktur macht die Nutzung numerischer Simulationen unabdingbar. So werden die Auswirkungen von Variationen der Transistorgeometrie sowie von Prozessparametern im Hinblick auf die Verspannung und die Drainstromänderungen der Transistoren neben den Messungen am gefertigten Transistor auch anhand numerischer Simulationen dargestellt und verglichen. Wesentliche Parameter für eine erhöhte Verspannung werden bestimmt und technologische Herausforderungen bei der Prozessintegration diskutiert. Die durchgeführten Simulationen und das erlangte Verständnis der Wirkungsweise der Verspannungstechniken ermöglichen es, das Potenzial dieser Verspannungstechniken für weitere Leistungssteigerungen in zukünftigen Technologiegenerationen abzuschätzen. Dadurch ist es möglich, die Prozessbedingungen und die Eigenschaften der fertigen Bauelemente im Hinblick auf eine gesteigerte Leistungsfähigkeit hin zu optimieren. Mit der weiteren Verkleinerung der Strukturgrößen der Bauelemente wird der zunehmende Einfluss der parasitären Source/Drain-Widerstände als Begrenzung der Effektivität der Verspannungstechniken identifiziert. Anschließend werden die Wechselwirkungen zwischen den einzelnen Verspannungstechniken hervorgehoben bzw. die gegebenenfalls auftretenden Einschränkungen angesprochen. Abschließend wird das Transportverhalten sowohl im linearen ohmschen Bereich als auch unter dem Einfluss hoher elektrischer Feldstärken analysiert und die deutlichen Unterschiede für die Leistungssteigerungen der verspannten n- und p-MOSFETs begründet. / As conventional MOSFET scaling is reaching its limits, several novel techniques are investigated to extend the CMOS roadmap. One of these techniques is the introduction of mechanical strain in the silicon transistor channel. Because strain changes the inter-atomic distances and thus the electronic band structure of silicon, ntype and p-type transistors with strained channels can show enhanced carrier mobility and performance. The purpose of this thesis is to analyze and understand the effects of strain on the electronic properties of planar silicon-on-insulator MOSFETs for high-performance applications as well as the optimization of various stress techniques and their technological limitations. First, the effect of strain on the electronic band structure of silicon and the carrier mobility is studied systematically using the empirical pseudopotential method and the deformation potential theory. Strain-induced energy band splitting and band deformations alter the electron and hole mobility through modulated effective masses and modified scattering rates. The various concepts for strain generation inside the transistor channel are reviewed. The focus of this work is on strained overlayer films, strained Si1-xGex and Si1-yCy in the source/drain regions, stress memorization techniques and strained substrates. It is shown, that strained silicon based improvements are highly sensitive to the device layout and geometry. For that reason, numerical simulations are indispensable to analyze the efficiency of the strain techniques to transfer strain into the channel. In close relation with experimental work the results from detailed simulation studies including parameter variations and material analyses are presented, as well as a thorough investigation of critical parameters to increase the strain in the transistor channel. Thus, the process conditions and the properties of the fabricated devices can be optimized with respect to higher performance. In addition, technological limitations are discussed and the potential of the different strain techniques for further performance enhancements in future technology generations is evaluated. With the continuing reduction in device dimensions the detrimental impact of the parasitic source/drain resistance on device performance is quantified and projected to be the bottleneck for strain-induced performance improvements. Next, the effects from a combination of individual strain techniques are studied and their interactions or possible restrictions are highlighted. Finally, the transport properties in the low-field transport regime as well as under high electrical fields are analyzed and the notable differences between strained n-type and p-type transistors are discussed.

In dieser Arbeit werden organische Feldeffekttransistoren (OFETs) aus den verschiedenen Materialien Manganphthalocyanin (MnPc), [6,6]Phenyl-C61-butansäuremethylester (PCBM), 6,13-Bis(triisopropylsilyethinyl)pentacen (TIPS-Pentacen) und N,N’- Bis(n-octyl)-1,6-Dicyanoperylen-3,4:9,10-Bis(Dicarboximid) (PDI8-CN2) hergestellt. Dabei finden unterschiedliche Abscheidemethoden wie die Molekularstrahlabscheidung, die Ultraschallsprühbeschichtung und die Drehbeschichtung Anwendung. Die Morphologie sowie die Funktionsweise der Transistoren werden in Abhängigkeit von den Herstellungsparametern und bezüglich ihrer Stabilität gegenüber Lufteinfluss und elektrischer Belastung charakterisiert. Durch Aufdampfen von MnPc konnten so zum ersten Mal ambipolare MnPc-OFETs hergestellt und charakterisiert werden. Die bestimmten Löcher- und Elektronenbeweglichkeiten bestätigen die Eignung von MnPc für die Anwendung in Spintronik-Bauelementen. Desweiteren wird anhand gesprühter PCBM- und TIPS-Pentacen-OFETs gezeigt, dass die Ultraschallsprühbeschichtung eine geeignete Technik ist, um organische Halbleiter aus Lösung für die Verwendung in OFETs abzuscheiden. Die Abscheidung organischer Filme lässt sich mit einer Vielzahl an Parametern beeinflussen und die Funktionsweise von OFETs optimieren. In Verbindung mit den Untersuchungen aufgeschleuderter PDI8-CN2-OFETs konnte ein erheblicher Einfluss der Oberflächenenergie des verwendeten SiO2-Gateisolators auf die Korngröße im organischen Film festgestellt werden.