Transistor Quantique InAs à Electrons Chauds: Fabrication submicronique et étude à haute fréquenceL'objectif de cette thèse est le développement de la technologie d'un transistor à électrons chauds constitué d'une hétérostructure quantique InAs/AlSb et exploitant un transport électronique résonant ultrarapide, le QHET (Quantum Hot Electron Transistor). Ce travail a permis l'étude approfondie de ses propriétés et performances à haute fréquence. L'étude aborde tous les aspects, de la conception, la croissance épitaxiale, la technologie de fabrication à la caractérisation statique et dynamique. Ce travail de thèse s'est effectué principalement à l'Institut d'Electronique du Sud (IES), sous la direction de Roland Teissier, et pour partie à l'Institut d'Electronique de Microélectronique et Nanotechnologie (IEMN) sous la direction de Mohamed Zaknoune. Nous avons, dans premier temps, mis en œuvre à l'IES une technologie double mésa afin de fabriquer les transistors avec l'émetteur de 10x10µm². La technologie en grande dimension est aisément réalisable et surtout reproductible. Elle nous a permis de travailler sur un grand nombre de structures transistor fabriquées par epitaxie par jets moléculaires (EJM) sur substrats InAs, afin d'en étudier le transport électronique et d'optimiser leur dessin. Le premier résultat marquant a été d'augmenter le gain statique jusqu'à une valeur de 15 grâce à une modification de la structure de l'émetteur qui une injection plus efficace puis l'utilisation d'une base fine de 85Å, qui améliore le temps de transit. Dans un deuxième temps, nous avons travaillé au sein de l'IES sur l'évolution de la technologie vers des dimensions intermédiaires dont la dimension la plus petite est de 1 µm de largeur. Cette technologie nous a donné une amélioration de performance des QHET grâce à la réduction des résistances et des capacités parasites des composants. Nous avons aussi travaillé à l'IEMN pour développer une technologie submicronique qui permet d'atteindre une largeur d'émetteur de 0.3 µm grâce à l'utilisation de la lithographie électronique. Cette technologie de fabrication plus performante nous a permis de mieux comprendre le fonctionnement du QHET. Et d'atteindre une régime de fonctionnement à forte densité de courant jusqu'à près de 1MA/ cm². Enfin, nous avons développé la structure et la technologie qui vont nous permettre d'évaluer la réponse à haute fréquence des QHET. Un point important a été de à disposer de la structure active du transistor sur un substrat isolant qui permette de réduire les éléments parasites durant la mesure en fréquence. Nous avons développé deux solutions : le transfert de substrat et la croissance métamorphique directement sur un substrat GaAs isolant.Les composants fabriqués par transfert de susbtrat présentent des valeurs de fréquence de transition FT de 77GHz et de fréquence d'oscillation FMAX de 88GHz. Les échantillons métamorphiques ont démontré de meilleures performances avec un FT de 170GHz et un FMAX supérieur à 200GHz. Ces résultats constituent les meilleurs dynamiques de transistors à électrons chauds à température ambiante. Ces études ont également fait progresser la compréhension du transport à haute fréquence dans ces composants. Ils permettent de comprendre les limitations actuelles et de proposer des pistes d'amélioration. / This work aims to develop a new high speed transistor in a vertical transport configuration that exploits the favourable transport properties of III-V semiconductor heterostructures based on InAs. This transistor is similar to a heterojunction bipolar transistor (HBT), but has theoretical assets to overcome the fundamental high speed limits of electron transport in HBT. Our approach uses the concept of hot electron transistor in an original InAs/AlSb quantum heterostructure, that we called a quantum hot electron transistor (QHET) or quantum cascade transistor (QCT). This research was almost done in Southern Electronics Institute (IES) under supervision of Dr. Roland Teissier and other work was realized in Micro-Nanotechnology Electronics Institute (IEMN) under supervision of Dr. Mohamed Zaknoune. The QHET is a unipolar vertical transport device made of a InAs/AlSb quantum heterostructure. Its first advantage over npn HBTs is the low base sheet resistance of 250 Ω/□ , accessible with moderate n-type doping levels (typically 1018 cm-3), which is a key parameter for high speed operation. Secondly, electron transport in the short (typically 100nm) bulk InAs collector is mostly ballistic with calculated transit times much shorter than in InP-based devices. We already developed the design and technology of QHET and demonstrated its resonant transports at cryogenic temperature and its improved static operation in smaller device. From these results, we come to develop our QHET structures to achieve high current gain. Using quantum design of thin base, the current gain is about 15. We fabricated QHET with emitter width scaled down to 0.3µm, using a state of the art electron beam lithography process. The junctions are defined using selective chemical etching. The base contact is self-aligned on the emitter contact. We achieved base resistance lower than 50Ω, comparable to state of the art HBTs. The small dimension allowed reaching the high current density regime of up to 1 MA/cm² required for high frequency operation. The static current gain is about 10, but could be increased up to 14 using a new quantum design. The collector breakdown voltage is greater than 1.2 V.Towards high frequency measurement, the substrate must be non-conducting material but InAs substrate is not available. Two technologies were proposed: transferred substrate and metamorphic substrate. For transferred substrate technology, we obtained a response of cutoff frequency of 77 GHz for FT and 88 for FMAX. For metamorphic substrate technology, we performed the growth of the transistor structures on a semi-insulating GaAs substrate. We used a thin GaSb buffer layer for metamorphic growth of the active part of the transistor, with an adequate growth procedure that allows forming mainly 90° misfit dislocations at the interface between the GaAs and GaSb. This technique permits more convenient and reliable processing of the devices, as compared to use of the more standard AlSb thick buffer layer. The frequency response was determined from S-parameters measured with a network analyser up to a frequency of 70 GHz. The measured gains, after de-embedding of the connection parasitic for a device with 0.5x4µm² emitter for JC=350kA/cm² (Ic= 6.0mA, Ib= 0.7mA, Vce=1.3V). The frequency dependence is not conventional on this device, with a resonance in the current gain close to 10 GHz and a slope different from -20 dB/decade for Mason's unilateral gains. Nevertheless, we could extract the cut-off frequencies FT=172 GHz from H21 and FMAX =230 GHz using -20dB/decade extrapolation of maximum stable gain (MSG). The present results confirmed the validity of this novel device concept. In addition, this is the first demonstration of the ability of a hot electron transistor to operate at high frequency at room temperature.

A high performance vertical organic transistor based on the organic semiconductor C60 is developed in this work. The sandwich geometry of this transistor, well known from organic light-emitting diodes or organic solar cells, allows for a short transfer length of charge carriers in vertical direction. In comparison to conventional organic field-effect transistors with lateral current flow, much smaller channel lengths are reached, even if low resolution and low-cost shadow masks are used. As a result, the transistor operates at low voltages (1 V), drives current densities in the range of 10 A/cm², and enables a switching speed in the MHz range. The operation mechanism is studied in detail. It is demonstrated that the transistor can be described by a nano-porous permeable base electrode insulated by a thin native aluminum oxide film on its surface. Thus, the transistor has to be understood as two metal-oxide-semiconductor diodes, sharing a common electrode, the base. Upon applying a bias to the base, charges accumulate in front of the oxide, similar to the channel formation in a field-effect transistor. Due to the increased conductivity in this region, charges are efficiently transported toward and through the pinholes of the base electrode, realizing a high charge carrier transmission. Thus, even a low concentration of openings in the base electrode is sufficient to ensure large transmission currents. The device concept turns out to be ideal for applications where high transconductance and high operation frequency are needed, e.g. in analog amplifier circuits. The full potential of the transistor is obtained if the active area is structured by an insulating layer in order to perfectly align the three electrodes. Besides that, molecular doping near the charge injecting contact is essential to minimize the contact resistance. Due to the high power density in the vertical C60 transistor, Joule self-heating occurs, which is discussed in this work in the context of organic semiconductors. The large activation energies of the electrical conductivity observed cause the presence of S-shaped current-voltage characteristics and result in thermal switching as well as negative differential resistances, as demonstrated for several two-terminal devices. A detailed understanding of these processes is important to determine restrictions and proceed with further optimizations.:CONTENTS Publications, patents and conference contributions 9 1 Introduction 13 2 Theory 19 2.1 From small molecules to conducting thin films . . . . . . . . . . . . . . . . . . . . 19 2.1.1 Aromatic hydrocarbons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1.2 Solid state physics of molecular materials . . . . . . . . . . . . . . . . . . . 24 2.1.3 Energetic landscape of an organic semiconductor . . . . . . . . . . . . . . 26 2.1.4 Charge transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.2 Semiconductor structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2.2.1 Semiconductor statistics and transport . . . . . . . . . . . . . . . . . . . . 42 2.2.2 Charge injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.2.3 Limitations of the current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 2.2.4 Metal-oxide-semiconductor structures . . . . . . . . . . . . . . . . . . . . . 57 2.3 Self-heating theory of thermistor device . . . . . . . . . . . . . . . . . . . . . . . . 61 3 Organic transistors 65 3.1 The organic field-effect transistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.1.1 Basic principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.1.2 Device characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 3.1.3 Device geometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.1.4 Device parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 3.1.5 Issues of OFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 3.1.6 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 3.2 Overview over vertical organic transistors . . . . . . . . . . . . . . . . . . . . . . . 76 3.2.1 VOTs with an unstructured base electrode . . . . . . . . . . . . . . . . . . . 76 3.2.2 VOTs with structured base electrode . . . . . . . . . . . . . . . . . . . . . . 79 3.2.3 Charge injection modulating transistors . . . . . . . . . . . . . . . . . . . . 82 3.2.4 Vertical organic field-effect transistor . . . . . . . . . . . . . . . . . . . . . . 85 3.2.5 Development of the scientific output . . . . . . . . . . . . . . . . . . . . . . 87 3.2.6 Competing technologies and approaches . . . . . . . . . . . . . . . . . . . 88 3.3 Vertical Organic Triodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3.1 Stucture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3.2 Electronic configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3.3 Energetic alignment of the diodes . . . . . . . . . . . . . . . . . . . . . . . 92 3.3.4 Current flow in the on and the off-state . . . . . . . . . . . . . . . . . . . . 94 3.3.5 Definition and extraction of parameters . . . . . . . . . . . . . . . . . . . . 95 4 Experimental 101 4.1 General processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.1.1 Thermal vapor deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.1.2 Processing tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 4.1.3 Processing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.2 Mask setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 4.3 Measurement setups and tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 4.3.1 Current-voltage measurements . . . . . . . . . . . . . . . . . . . . . . . . . 108 4.3.2 Frequency-dependent measurements . . . . . . . . . . . . . . . . . . . . . 108 4.3.3 Impedance Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.3.4 Ultraviolet and X-ray Photoelectron Spectroscopy . . . . . . . . . . . . . . . 110 4.3.5 Thermal imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 4.4 Materials used in C60 triodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.4.1 Buckminsterfullerene C60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.4.2 Tungsten paddlewheel W2(hpp)4 . . . . . . . . . . . . . . . . . . . . . . . . 116 4.4.3 Aluminum and its oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 4.4.4 Spiro-TTB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 4.5 Materials used in Organic Light-emitting Diodes . . . . . . . . . . . . . . . . . . . 121 5 Introduction of C60 VOTs 123 5.1 Sample preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.2 Diode characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.3 Base sweep measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 5.4 Determination of parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 5.5 Common-base connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.6 Output characteristic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 5.7 Frequency-dependent measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 137 5.8 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 6 Effect of annealing 141 6.1 Charge carrier transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 6.2 Sheet resistance and transmittance of the base electrode . . . . . . . . . . . . . . 142 6.3 Investigation of morphological changes . . . . . . . . . . . . . . . . . . . . . . . . 144 6.4 Photoelectron spectroscopy of the base electrode . . . . . . . . . . . . . . . . . . 153 6.5 Influence of air exposure and annealing onto the dopants . . . . . . . . . . . . . . 159 6.6 Electrical characteristics of the diodes . . . . . . . . . . . . . . . . . . . . . . . . . 162 6.7 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 7 Working Mechanism 167 7.1 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7.2 Diode characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7.3 Simulation and modeling of the diode characteristics . . . . . . . . . . . . . . . . . 173 7.4 Interpretation of the operation mechanism . . . . . . . . . . . . . . . . . . . . . . . 181 7.5 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 8 Optimization of VOTs 183 8.1 Misalignment of the electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 8.2 Use of doping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 8.3 Variation of the intrinsic layer thickness . . . . . . . . . . . . . . . . . . . . . . . . . 190 8.4 Structuring the active area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 8.5 High-frequency operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 8.6 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 9 Self-heating in organic semiconductors 209 9.1 Temperature activation in C60 triodes . . . . . . . . . . . . . . . . . . . . . . . . . . 210 9.2 nin-C60 crossbar structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 9.3 Thermal switching in organic semiconductors . . . . . . . . . . . . . . . . . . . . . 216 9.4 Self-heating in large area devices: Organic LEDs . . . . . . . . . . . . . . . . . . . 218 9.5 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 10 Conclusion and Outlook 227 10.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 10.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 A Appendix 233 A.1 Appendix 1: Accuracy of the current gain . . . . . . . . . . . . . . . . . . . . . . . 233 A.2 Appendix 2: Fit of XRR measurements . . . . . . . . . . . . . . . . . . . . . . . . . 234 A.3 Appendix 3: Atomic force microscopy . . . . . . . . . . . . . . . . . . . . . . . . . 236 A.4 Appendix 4: Transmission electron microscopy . . . . . . . . . . . . . . . . . . . . 236 A.5 Appendix 5: Drift-diffusion simulation of nin devices . . . . . . . . . . . . . . . . . 239 A.6 Appendix 6: A simple parallel thermistor circuit . . . . . . . . . . . . . . . . . . . . 241 List of Figures 245 References 290 / In dieser Arbeit wird ein vertikaler organischer Transistor mit hoher Leistungsfähigkeit vorgestellt, der auf dem organischen Halbleiter C60 basiert. Die von organischen Leuchtdioden und organischen Solarzellen bekannte \'Sandwich’-Geometrie wird verwendet, so dass es möglich ist, für die vertikale Stromrichtung kurze Transferlängen der Ladungsträger zu erreichen. Im Vergleich zum konventionellen organischen Feldeffekttransistor mit lateralem Stromfluss werden dadurch viel kleinere Kanallängen erreicht, selbst wenn preisgünstige Schattenmasken mit geringer Auflösung für die thermische Verdampfung im Vakuum genutzt werden. Daher kann der Transistor bei einer Betriebsspannung von 1 V Stromdichten im Bereich von 10 A/cm² und Schaltgeschwindigkeiten im MHz-Bereich erreichen. Obwohl diese Technologie vielversprechend ist, fehlt bislang ein umfassendes Verständnis des Funktionsmechanismus. Hier wird gezeigt, dass der Transistor eine nanoporöse Basiselektrode hat, die durch ein natives Oxid auf ihrer Oberfläche elektrisch isoliert ist. Daher kann das Bauelement als zwei Metall-Oxid-Halbleiter-Dioden verstanden werden, die sich eine gemeinsame Elektrode, die Basis, teilen. Unter Spannung akkumulieren Ladungsträger vor dem Oxid, ähnlich zur Ausbildung eines Ladungsträgerkanals im Feldeffekttransistor. Aufgrund der erhöhten Leitfähigkeit in dieser Region werden Ladungsträger effizient zu und durch die Öffnungen der Basis transportiert, was zu hohen Ladungsträgertransmissionen führt. Selbst bei einer geringen Konzentration von Löchern in der Basiselektrode werden so hohe Transmissionsströme erzielt. Das Bauelementkonzept ist ideal für Anwendungen, in denen eine hohe Transkonduktanz und eine hohe Schaltgeschwindigkeit erreicht werden soll, z.B. in analogen Schaltkreisen, die kleine Signale verarbeiten. Das volle Potential des Transistors offenbart sich jedoch, wenn die aktive Fläche durch eine Isolatorschicht strukturiert wird, um den Überlapp der drei Elektroden zu optimieren, so dass Leckströme minimiert werden. Daneben ist die Dotierung der Molekülschichten am Emitter essentiell, um Kontaktwiderstände zu vermeiden. Aufgrund der hohen Leistungsdichten in den vertikalen C60-Transistoren kommt es zur Selbsterwärmung, die in dieser Arbeit im Kontext organischen Halbleiter diskutiert wird. Die große Aktivierungsenergie der Leitfähigkeit führt zu S-förmigen Strom-Spannungs-Kennlinien und hat thermisches Umschalten sowie negative differentielle Widerstände zur Folge, was für verschiedene Bauelemente demonstriert wird. Ein detailliertes Verständnis dieser Prozesse ist wichtig, um Beschränkungen für Anwendungen zu erkennen und um entsprechende Verbesserungen einzuführen.:CONTENTS Publications, patents and conference contributions 9 1 Introduction 13 2 Theory 19 2.1 From small molecules to conducting thin films . . . . . . . . . . . . . . . . . . . . 19 2.1.1 Aromatic hydrocarbons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1.2 Solid state physics of molecular materials . . . . . . . . . . . . . . . . . . . 24 2.1.3 Energetic landscape of an organic semiconductor . . . . . . . . . . . . . . 26 2.1.4 Charge transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.2 Semiconductor structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2.2.1 Semiconductor statistics and transport . . . . . . . . . . . . . . . . . . . . 42 2.2.2 Charge injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.2.3 Limitations of the current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 2.2.4 Metal-oxide-semiconductor structures . . . . . . . . . . . . . . . . . . . . . 57 2.3 Self-heating theory of thermistor device . . . . . . . . . . . . . . . . . . . . . . . . 61 3 Organic transistors 65 3.1 The organic field-effect transistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.1.1 Basic principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.1.2 Device characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 3.1.3 Device geometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.1.4 Device parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 3.1.5 Issues of OFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 3.1.6 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 3.2 Overview over vertical organic transistors . . . . . . . . . . . . . . . . . . . . . . . 76 3.2.1 VOTs with an unstructured base electrode . . . . . . . . . . . . . . . . . . . 76 3.2.2 VOTs with structured base electrode . . . . . . . . . . . . . . . . . . . . . . 79 3.2.3 Charge injection modulating transistors . . . . . . . . . . . . . . . . . . . . 82 3.2.4 Vertical organic field-effect transistor . . . . . . . . . . . . . . . . . . . . . . 85 3.2.5 Development of the scientific output . . . . . . . . . . . . . . . . . . . . . . 87 3.2.6 Competing technologies and approaches . . . . . . . . . . . . . . . . . . . 88 3.3 Vertical Organic Triodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3.1 Stucture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3.2 Electronic configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3.3 Energetic alignment of the diodes . . . . . . . . . . . . . . . . . . . . . . . 92 3.3.4 Current flow in the on and the off-state . . . . . . . . . . . . . . . . . . . . 94 3.3.5 Definition and extraction of parameters . . . . . . . . . . . . . . . . . . . . 95 4 Experimental 101 4.1 General processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.1.1 Thermal vapor deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.1.2 Processing tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 4.1.3 Processing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.2 Mask setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 4.3 Measurement setups and tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 4.3.1 Current-voltage measurements . . . . . . . . . . . . . . . . . . . . . . . . . 108 4.3.2 Frequency-dependent measurements . . . . . . . . . . . . . . . . . . . . . 108 4.3.3 Impedance Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.3.4 Ultraviolet and X-ray Photoelectron Spectroscopy . . . . . . . . . . . . . . . 110 4.3.5 Thermal imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 4.4 Materials used in C60 triodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.4.1 Buckminsterfullerene C60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.4.2 Tungsten paddlewheel W2(hpp)4 . . . . . . . . . . . . . . . . . . . . . . . . 116 4.4.3 Aluminum and its oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 4.4.4 Spiro-TTB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 4.5 Materials used in Organic Light-emitting Diodes . . . . . . . . . . . . . . . . . . . 121 5 Introduction of C60 VOTs 123 5.1 Sample preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.2 Diode characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.3 Base sweep measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 5.4 Determination of parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 5.5 Common-base connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.6 Output characteristic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 5.7 Frequency-dependent measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 137 5.8 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 6 Effect of annealing 141 6.1 Charge carrier transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 6.2 Sheet resistance and transmittance of the base electrode . . . . . . . . . . . . . . 142 6.3 Investigation of morphological changes . . . . . . . . . . . . . . . . . . . . . . . . 144 6.4 Photoelectron spectroscopy of the base electrode . . . . . . . . . . . . . . . . . . 153 6.5 Influence of air exposure and annealing onto the dopants . . . . . . . . . . . . . . 159 6.6 Electrical characteristics of the diodes . . . . . . . . . . . . . . . . . . . . . . . . . 162 6.7 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 7 Working Mechanism 167 7.1 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7.2 Diode characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7.3 Simulation and modeling of the diode characteristics . . . . . . . . . . . . . . . . . 173 7.4 Interpretation of the operation mechanism . . . . . . . . . . . . . . . . . . . . . . . 181 7.5 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 8 Optimization of VOTs 183 8.1 Misalignment of the electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 8.2 Use of doping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 8.3 Variation of the intrinsic layer thickness . . . . . . . . . . . . . . . . . . . . . . . . . 190 8.4 Structuring the active area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 8.5 High-frequency operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 8.6 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 9 Self-heating in organic semiconductors 209 9.1 Temperature activation in C60 triodes . . . . . . . . . . . . . . . . . . . . . . . . . . 210 9.2 nin-C60 crossbar structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 9.3 Thermal switching in organic semiconductors . . . . . . . . . . . . . . . . . . . . . 216 9.4 Self-heating in large area devices: Organic LEDs . . . . . . . . . . . . . . . . . . . 218 9.5 Intermediate summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 10 Conclusion and Outlook 227 10.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 10.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 A Appendix 233 A.1 Appendix 1: Accuracy of the current gain . . . . . . . . . . . . . . . . . . . . . . . 233 A.2 Appendix 2: Fit of XRR measurements . . . . . . . . . . . . . . . . . . . . . . . . . 234 A.3 Appendix 3: Atomic force microscopy . . . . . . . . . . . . . . . . . . . . . . . . . 236 A.4 Appendix 4: Transmission electron microscopy . . . . . . . . . . . . . . . . . . . . 236 A.5 Appendix 5: Drift-diffusion simulation of nin devices . . . . . . . . . . . . . . . . . 239 A.6 Appendix 6: A simple parallel thermistor circuit . . . . . . . . . . . . . . . . . . . . 241 List of Figures 245 References 290

Die vorliegende Arbeit behandelt die Herstellung geordneter C60-Schichten, ihre elektrochemische Nanostrukturierung in wässrigen Lösungen und ionischen Flüssigkeiten und den Einsatz geordneter und nanostrukturierter Fullerenschichten in organischen Dünnschichttransistoren. Geordnete C60-Schichten wurden durch thermische Verdampfung im Hochvakuum hergestellt. Als Substratmaterial wurden HOPG (Graphit), Glimmer und einkristallines Silizium verwendet. Die größten einkristallinen Bereiche werden auf HOPG-Substraten erhalten. Die laterale Ausdehnung der C60-Kristallite parallel zu den Graphitstufen kann bis zu 50 µm erreichen, orthogonal zu den Stufen ist das Wachstum durch die Graphitstufen begrenzt. Die elektrochemische Reduktion von C60 -Schichten in wässriger Lösung ist elektrochemisch irreversibel. Die geflossene Ladung beträgt ein Vielfaches der theoretisch möglichen Menge. Durch die Reduktion tritt eine Nanostrukturierung der Schichtoberfläche ein, die Größe der gebildeten Cluster beträgt 20 nm bis 50 nm. Fullerenpolymere und hydriertes C60 sind die chemischen Hauptprodukte der elektrochemischen Nanostrukturierung in wässriger Lösung. Die Reduktion von Fullerenschichten in ionischen Flüssigkeiten ist aufgrund der geschlossenen Schichtoberfläche und des starken Potentialabfalls in der Fullerenschicht zunächst kinetisch gehemmt und setzt erst bei negativeren Potentialen im Bereich der Reduktion zum C60-Dianion ein. Die Reduktion der Fullerenschichten ist elektrochemisch irreversibel, zum Teil aber chemisch reversibel. Es konnte erstmals der Einsatz nanostrukturierter C60 -Schichten als aktives Halbleitermaterial in Feldeffekt-Transistoren gezeigt werden. Für die Verwendung nanostrukturierter Fullerenschichten in Feldeffekt-Transistoren wurde 11-(3-Thienyl-)undecyl-trichlorosilan als Haftvermittler eingesetzt. Die gezeigten Ergebnisse von C60 -Transistoren mit hoher Ladungsträgerbeweglichkeit und der erfolgreichen Verwendung nanostrukturierter Fullerenschichten in Transistorstrukturen zeigen die Möglichkeiten des C60 als aktives Halbleitermaterial auf.

No description available.

Planar electronic devices represent an attractive approach towards roll-to-roll printed electronics without the need for the sequential, precisely aligned, patterning steps inherent in the fabrication of conventional ‘3D’ electronic devices. Self-switching diodes (SSDs) and in-plane-gate field-effect transistors (IPG-FETs) can be patterned using a single process into a substrate precoated with semiconductor.These devices function in depletion mode, requiring the semiconductor to be doped in order for the devices to function. To achieve this, a reliable and controllable method was developed for doping organic semiconducting polymers by the immersion of optimally deposited films in a solution of dopant. The process was shown to apply both semicrystalline and air-stable, amorphous materials indicating that the approach is broadly applicable to a wide range of organic semiconductors.Simultaneously with the development of the doping protocol specialised hot-embossing equipment was designed and constructed and a high-yielding method of patterning the structures of IPG-FETs and SSDs was arrived at. This method allowed for consistent and reliable patterning of features with a minimum line-width of 200nm.Following the development of these doping and patterning processes these were combined to fabricate controllably doped, functioning planar devices. SSDs showed true zero-threshold rectification behaviour with no observed breakdown in the reverse direction up to 100 V. IPG-FETs showed switching behaviour in response to an applied gate potential and were largely free of detectable gate leakage current, verifying the quality of the patterning process.Furthermore, high-performance semiconducting polymer PAAD was synthesised and characterised in field-effect transistors as steps towards its use in planar electronic devices. It was also shown that this material could be doped using the developed immersion doping protocol and that this protocol was compatible with top-gated device architectures and the use of fluoropolymer CYTOP as a dielectric.

Résumé : Le transistor monoélectronique (SET) est un dispositif nanoélectronique très attractif à cause de son ultra-basse consommation d’énergie et sa forte densité d’intégration, mais il n’a pas les capacités suffisantes pour pouvoir remplacer complètement la technologie CMOS. Cependant, la combinaison de la technologie SET avec celle du CMOS est une voie intéressante puisqu’elle permet de profiter des forces de chacune, afin d’obtenir des circuits avec des fonctionnalités additionnelles et uniques. Cette thèse porte sur l’intégration 3D monolithique de nanodispositifs dans le back-end-of-line (BEOL) d’une puce CMOS. Cette approche permet d’obtenir des circuits hybrides et de donner une valeur ajoutée aux puces CMOS actuelles sans altérer le procédé de fabrication du niveau des transistors MOS. L’étude se base sur le procédé nanodamascène classique développé à l’UdeS qui a permis la fabrication de dispositifs nanoélectroniques sur un substrat de SiO2. Ce document présente les travaux réalisés sur l’optimisation du procédé de fabrication nanodamascène, afin de le rendre compatible avec le BEOL de circuits CMOS. Des procédés de gravure plasma adaptés à la fabrication de nanostructures métalliques et diélectriques sont ainsi développés. Le nouveau procédé nanodamascène inverse a permis de fabriquer des jonctions MIM et des SET métalliques sur une couche de SiO2. Les caractérisations électriques de MIM et de SET formés avec des jonctions TiN/Al2O3 ont permis de démontrer la présence de pièges dans les jonctions et la fonctionnalité d’un SET à basse température (1,5 K). Le transfert de ce procédé sur CMOS et le procédé d’interconnexions verticales sont aussi développés par la suite. Finalement, un circuit 3D composé d’un nanofil de titane connecté verticalement à un transistor MOS est réalisé et caractérisé avec succès. Les résultats obtenus lors de cette thèse permettent de valider la possibilité de co-intégrer verticalement des dispositifs nanoélectroniques avec une technologie CMOS, en utilisant un procédé de fabrication compatible. / Abstract : The single electron transistor (SET) is a nanoelectronic device very attractive due to its ultra-low power consumption and its high integration density, but he is not capable of completely replace CMOS technology. Nevertheless, the hybridization of these two technologies is an interesting approach since it combines the advantages of both technologies, in order to obtain circuits with new and unique functionalities. This thesis deals with the 3D monolithic integration of nanodevices in the back-end-ofline (BEOL) of a CMOS chip. This approach gives the opportunity to build hybrid circuits and to add value to CMOS chips without fundamentally changing the process fabrication of MOS transistors. This study is based on the nanodamascene process developed at UdeS, which is used to fabricate nanoelectronic devices on a SiO2 layer. This document presents the work done on the nanodamascene process optimization, in order to make it compatible with the BEOL of CMOS circuits. The development of plasma etching processes has been required to fabricate metallic and dielectric nanostructures useful to the fabrication of nanodevices. MIM junctions and metallic SET have been fabricated with the new reverse nanodamascene process on a SiO2 substrate. Electrical characterizations of MIM devices and SET formed with TiN/Al2O3 junctions have shown trap sites in the dielectric and a functional SET at low temperature (1.5 K). The transfer process on CMOS substrate and the vertical interconnection process have also been developed. Finally, a 3D circuit consisting of a titanium nanowire connected to a MOS transistor is fabricated and is functional. The results obtained during this thesis prove that the co-integration of nanoelectronic devices in the BEOL of a CMOS chip is possible, using a compatible process.

Dans ce projet de thèse, qui s'appuie sur l'optimisation d'un réacteur de croissance du diamant et la construction d'un prototype, nous avons démontré l'épitaxie par étapes de couches de diamant, orientées (100), lourdement dopées au bore sur des couches de dopage plus faible dans le même processus, sans arrêter le plasma. Plus original, nous avons démontré la situation inverse. Nous présentons aussi des croissances assez lentes pour l'épitaxie de films d'épaisseur nanométriques avec de grands sauts de dopage, appelé delta-dopage. L'accent a été porté sur le gain en raideur des interfaces. Nous démontrons la présence d'interfaces fortement abruptes, issues de gravures in-situ optimisées, par une analyse conjointe en spectrométrie de masse à ionisation secondaire et en microscopie électronique en transmission à balayage en champ sombre annulaire aux grands angles. Des super-réseaux de dopages abrupts montrent des pics satellites de diffraction X typiques de la super-période. / The aim of this PhD thesis was to better understand the boron delta-doping of diamond over building a new Microwave Plasma Chemical Vapour Deposition reactor prototype. We succeed to grow step by step heavy on low, and more original, low on heavy boron-doped layers of (100)-oriented diamond in the same process and without stopping the plasma. We also settled growth parameters for a growth rate slow enough to get nanometre-thick homoepitaxial films with boron doping jumps over several orders of magnitude, called delta-doping. We demonstrated the presence of super-sharp interfaces, after optimized in situ etching, by joint Secondary Ion Mass Spectrometry and Scanning Tunneling Electron Microscopy at High-Angle Annular Dark Field analysis. Finally superlattices with abrupt boron doping levels have been grown; they show satellite peaks of X-ray diffraction representative of a super-period.

O projeto de amplificadores de baixo ruído (LNA) aparenta ser um trabalho simples pelos poucos componentes ativos e passivos que o compõe, porém a alta correlação entre os seus parâmetros de projeto dificulta muito esse trabalho. Esta dissertação apresenta uma proposta para contornar essa dificuldade: o uso de algoritmos metaheurísticos, em particular algoritmos genéticos e simulated annealing. Algoritmos metaheurísticos são técnicas avançadas que emulam princípios físicos ou naturais para resolver problemas com alto grau de complexidade. Esses algoritmos estão emergindo nos últimos anos porque têm mostrado eficiência e eficácia. São feitos neste trabalho os projetos de três LNAs, dois (LNA1 e LNA2) para sistemas com arquitetura homódine (LNA com carga capacitiva) e um (LNA3) para sistemas com arquitetura heteródine (LNA com carga resistiva) utilizando-se algoritmos genéticos e simulated annealing (recozimento simulado). Apresenta-se inicialmente a análise detalhada da configuração escolhida para os projetos (fonte comum cascode com degeneração indutiva FCCDI). A frequência de operação dos LNAs é 1,8 GHz e a fonte de alimentação de 2,0 V. Para o LNA1 e o LNA2 se atingiu uma figura de ruído de 2,8 dB e 3,2 dB, consumo de potência de 6,8 mW e 2,7 mW e ganho de tensão de 22 dB e 24 dB, respectivamente. Para LNA3 se atingiu uma figura de ruído de 3,5 dB, consumo de potência de 7,8 mW e ganho de tensão de 15,5 dB. Os resultados obtidos e comparações feitas com LNAs da literatura demonstram viabilidade e eficácia da aplicação de algoritmos metaheurísticos no projeto de LNA. Neste trabalho utilizaram-se as ferramentas ELDO (simulador de circuitos elétricos), versão 2009.1 patch1 64 bits, ASITIC (para projetar e simular os indutores), versão 03.19.00.0.0.0 e MATLAB (o toolbox fornece os algoritmos metaheurísticos), versão 7.9.0.529 R2009b. Além disso, os projetos foram desenvolvidos na tecnologia CMOS 0,35 m da AMS (Austria Micro Systems). / The design of low noise amplifiers (LNA) seems to be a simple work because the small number of active and passive device that they are composes, nevertheless the high trade off of LNA parameters complicates very much the work. This research presents a proposal to contour act the obstacle: to use metaheuristic algorithms, in special genetic algorithms and simulated annealing. The metaheuristic algorithms are advanced techniques that emulate physics or natural principles to solve problems with high grade of complexity. They have been emerging in the last years because they have shown effectiveness and efficiency. In this dissertation were designed three LNAs using genetic algorithms and simulated annealing: two (LNA1 and LNA2) to homódine architecture (LNA with capacitive load) and one (LNA3) to heteródine architecture (LNA with resistive load). First it is show the detailed analysis of configuration chosen to the designs (common source cascode with inductive degeneration). The operation frequency is 1.8 GHz and power supply is 2.0 V for all LNAs. LNA1 and LNA2 reached a noise figure of 2.8 dB and 3.2 dB, a dissipation power of 6.8 mW and 2.7 mW, and a voltage gain of 22 dB and 24 dB respectively. LNA3 reached 3.5 dB of noise figure, 7.8 mW of dissipation power, and 15.5 dB of voltage gain. The results obtained and the comparisons with LNAs from the literature demonstrate that the metaheuristic algorithms show efficiency and effectiveness in the design of LNA. This study was developed with the help of the tools ELDO (electric circuit simulator) version 2009.1 patch1 64 bits, ASITIC (to design and simulate the inductors) version 03.19.00.0.0.0, and MATLAB (the toolbox provides the metaheuristic algorithms) version 7.9.0.529 R2009b. Furthermore, the designs were developed on CMOS 0.35 AMS (Austria Micro Systems) technology.

A eletrônica digital desempenha papel essencial no desenvolvimento e manutenção dos padrões de vida em prática hoje no mundo. A peça fundamental para a criação desta era tecnológica é sem dúvidas o transistor. Com o advento de novos materiais, a busca por transistores que oferecem novas oportunidades de processamento e aplicação permitiu que uma nova área fosse criada: a eletrônica orgânica. Transistores de efeito de campo baseados em filmes finos de materiais orgânicos têm recebido grande atenção nas últimas décadas. Apresentamos um estudo experimental e teórico de transistores de efeito de campo a base de filmes finos orgânicos. Foram caracterizados transistores usando um derivado do pentaceno (TMTES-pentaceno) como camada ativa em um dispositivo feito sobre Si/SiO2. Mostramos que a inclusão do semicondutor orgânico em uma matriz polimérica isolante ajuda a manter a estabilidade termo mecânica do dispositivo. Foi desenvolvido um modelo que levasse em conta as resistências parasíticas para explicar o comportamento do transistor em função da temperatura. Também foram construídos e caracterizados transistores usando rr-P3HT como semicondutor e PMMA como isolantes. Apresentamos transistores do tipo Top-Gate e Bottom-Gate com mobilidade máxima de 7 x 10-3 cm2/V.s. Valores de razão ON/OFF de ~ 900 foram encontrados nos transistores otimizados. O comportamento dos transistores é analisado em função da temperatura e os modelos de aproximação de canal gradual e de Vissenberg-Matters foram aplicados para extração dos parâmetros de interesse. Por fim, apresentamos um modelo de corrente de canal baseado na resolução 2D numérica da equação de Poisson usando as idéias de Vissenberg-Matters para a concentração de cargas em função do potencial local. O modelo, embora ainda nos primeiros estágios de desenvolvimento, prevê a saturação da corrente nas curvas de saída simuladas sem limitações de regime de validade. / Digital electronics plays an essential role in the development and maintenance of living standards into practice in the world today. The cornerstone for the creation of this technological age is undoubtedly the transistor. With the advent of new materials, the search for transistors that offer new opportunities in processing and application allowed a new area to be created: the organic electronics. Field effect transistors based on organic thin films have received great attention in recent decades. We report an experimental and theoretical study of field effect transistors based on organic thin films. We characterized transistors manufactured using a derivative of pentacene (TMTES-pentacene) as the active layer in a device and using Si/SiO2 as gate and insulator. We show that the inclusion of the organic semiconductor in an insulating polymeric matrix helps to maintain the termo-mechanical stability of the device. A model was developed that take into account the parasitic resistances and to explain the behavior of the transistor as a function of temperature. We also present the manufacturing and characterization process of transistors using rr-P3HT as semiconductor and PMMA as insulator. We report Top-Gate and Bottom-Gate transistors with maximum mobility of 7 x 10-3 cm2/V.s. The maximun ON/OFF ratio of ~ 900 was found for the optimized transistors. The behavior of the transistors was analyzed as a function of temperature and both gradual channel approximation and Vissenberg-Matters models were applied for extracting the parameters. Finally, we present a channel current model based on the resolution of 2D numerical Poisson equation using the ideas of Vissenberg-Matters to the calculate the concentration of charges due to the local potential. The model, although still in the early stages of development, predicts the saturation current at output simulated curves with no limitation of regime validity.

Os efeitos da radiação ionizante em dispositivos eletrônicos é uma preocupação crescente na tecnologia de semicondutores, especialmente devido à contínua redução dos dispositivos e ainda maior, quando são destinados para uso em ambientes agressivos com alta radiação, tais como missões espaciais, aceleradores de partículas ou reatores nucleares. Dentre os vários efeitos causados pela radiação ionizante em dispositivos eletrônicos está aquele devido à Dose Acumulada (Total Ionizing Dose - TID), o qual a acumulação de danos de radiação no dispositivo muda seu funcionamento normal. O TID causado por fótons em transístores já foi estudado no Brasil, mas o efeito de prótons num transistor bipolar, apresentado neste trabalho é um trabalho pioneiro no país. As curvas características de um transistor 2N3733 foram medidas antes, durante e após a irradiação de prótons entre 1,5 e 3,8 MeV, para quantificar as alterações das especificações elétricas do dispositivo. Nestas energias, há uma correlação direta entre a mudança na resposta elétrica e a energia do próton, exceto em algumas energias específicas, onde o pico de Bragg ocorreu perto das junções ou no meio do cristal de silício, demonstrando a importância da correta caracterização da camada de passivação em estudos de TID em dispositivos eletrônicos. A recuperação dos transistores irradiados após o recozimento a 50°C durante 8 horas também foi maior para aqueles irradiados nessas energias. Existe um limite superior de dose para o qual não foi observada alteração significativa do transistor. Este limite, da ordem de Grad, excede a maioria das aplicações em ambientes terrestres, mas está dentro do intervalo esperado para missões espaciais a Júpiter ou em grandes aceleradores de partículas. / The effect of ionizing radiation on electronic devices is a growing concern in semiconductor technology, especially due to the continuous reduction of the devices and even greater when they are intended for use in aggressive environments with high radiation, such as space missions, particle accelerators or nuclear reactors. Among the various effects caused by ionizing radiation on electronic devices are the effects due to Total Ionizing Dose (TID), in which the accumulation of radiation damage in the device changes its normal functioning. The TID caused by photons has already been studied in Brazil, but the effect of protons on a bipolar transistor, presented in this work is a pioneer work in the country. The characteristic curves of a 2N3733 transistor were measured before, during and after proton irradiation between 1.5 and 3.8 MeV, to quantify changes of the electrical specifications of the device. At these proton energies, there is a direct correlation between the change in the electric response to the proton energy, except at some specific energies where the Bragg peak occurred near the junctions or in the middle of the silicon crystal, demonstrating the importance of the correct characterization of the passivation layer in TID studies of electronic devices. The recovery of transistors irradiated after annealing at 50 ° C for 8 hours was also higher for those irradiated at these energies. There is an upper dose limit for which no alteration of the transistor was observed. This limit, of the order of Grad, exceeds most applications in terrestrial environments, but is within the expected range for space missions to Jupiter or large particle accelerators.