Neste trabalho estudamos as estruturas e as mobilidades eletrônicas em um sistema quase-bidimensional de poços quânticos parabólicos de AlxGa1-xAs dopados. Obtemos as auto-energias, as funções de onda e os perfis dos potencias de confinamento efetivo no sistema, através das soluções numéricas das equações de Schrödinger e de Poisson de forma autoconsistente. Em particular, estudamos as mobilidades quânticas e de transporte nestes sistemas. Devido a ocupação de várias subbandas nestes sistemas, as contribuições dos espalhamentos inter-subbandas para as mobilidades têm a mesma importância que os espalhamentos intra-subbandas. Obtemos as mobilidades de cada subbanda devido aos espalhamentos por impurezas doadoras e aceitadoras ionizadas e por potencial de liga. Analisamos os efeitos das distribuições de doadores dopados, de aceitadores de fundo e do potencial de gate externo / In this work we study the electronic structure and electron mobilities in doped wide parabolic quantum wells of AlxGa1-xAs. The subband energies, the wavefunctions, and the effective confining potential profile are obtained by studying selfconsistently the coupled Schrödinger and Poisson equations. Based on the numerical results of the electronic structure, we calculate the quantum and transport mobilities of the system. Usually several subbands are occupied in such systems and they are strongly coupled to each other, the intersubband interaction shows the same importance as the intrasubband one to the electronic transport. We study and analyze the electron mobility of each subband due to the ionized donor scattering and the alloy scattering. We also show the effect of ionized background acceptor impurity scattering

Cars have become necessities of our daily life and are especially important to people with disability because they extend their range of activity and allow participation in a social life. Sometimes driving a normal car is impossible for individuals with severe disability and they require additional driving aide. However, it is dangerous to send these individuals on the road without giving them special training on driving vehicles using an adaptive aide. Nowadays there are a number of driving simulators that train disabled persons but none of them have joystick-enabled training that controls both steering, gas and break pedal. This necessitates the design of a method and a system which helps a person with disabilities learn how to operate a joystick-enabled vehicle, by using a combination of an advanced vehicle interface system, which is a driving aide known as Advanced Electronic Vehicle Interface Technology (AVEIT) and virtual reality driving simulator known as Simulator Systems International (SSI). This thesis focuses on the mechanism that synchronizes both AVEIT and SSI systems. This was achieved by designing a mechanical and electrical system that serves as a means of transferring the action between the AVEIT and SSI system. The mechanical system used for this purpose consists of two coupler units attached to AVEIT and SSI each combined together by the electrical system. As the user operates the joystick, the action of AVEIT is transferred to the SSI system by the help of the electromechanical system. The design provides compatibility between the AVEIT and SSI system which makes them convenient for training persons with disability.

Abstract ¡@¡@Biosensor chip has a lot of advantages, such as label-free, ultra-sensitive, highly selective, fast and real-time detection. Fabricating biosensor chip has great benefits for gene-detection, protein-detection, medical diagnosis and development of new medicine. This research will integrate the biomedical, chemistry, and physics, and also combined with biochemical technology and semiconductor technology to produce biosensor chip. ¡@¡@We use microelectronic semiconductor process technology to fabricate silicon nanowire field effect transistors (SiNW-FET). The source-drain current versus the voltage curve (Isd-Vsd) shows that the contact pad and the silicon nanowire form ohmic contact. And then we use chemical surface modification technologies to modified biotin on SiNW-FET to detect streptavidin. ¡@¡@In addition, we also grow AlGaN/GaN film by MBE, and fabricate nitride¡Vbased high electron mobility transistor (HEMT) by microelectronic semiconductor process technology. In this study, we apply HEMT in biosensor for pancreatic cancer marker CA19-9 antigen. And we modify pancreatic cancer marker CA19-9 antibody on the biosensor chip surface to detect pancreatic cancer marker CA19-9 antigen molecule. ¡@¡@Most of biomolecules are with weak charges, which can form chemical gating effect and change the conductance of p-type SiNW. And according to the streptavidin microfluidic measurement of biotin-modified SiNW-FET, the detection limit of streptavidin was 10-9 M. And the detection limit of pancreatic cancer marker CA19-9 antigen for N-HEMT biosensor was 150 U/mL.

III-nitrides are a promising material system with unique material properties, which allows them to be utilized in a variety of semiconductor devices. III-nitrides grown by NH3-MOMBE are typically grown with high carbon levels (> 1021 cm-3) as a result of the incomplete surface pyrolysis of the metal-organic sources. Recent research has involved the compensating nature of carbon in III-nitrides to produce semi-insulating films, which can provide low-leakage buffer layers in transistor devices. The aim of this work is to investigate the possibility of forming a 2DEG, which utilizes the highly carbon-doped GaN layers grown by NH3-MOMBE to produce low-leakage buffer layers in the fabrication of HEMTs. These low leakage GaN buffers would provide increased HEMT performance, with better pinch-off, higher breakdown voltages and increased power densities. Additionally, methods of controlling and/or reducing the incorporation of carbon will be undertaken in an attempt to broaden the range of possible device applications for NH3-MOMBE. To realize these transistor devices, optimization and improved understanding of the growth conditions for both GaN and AlGaN will be explored with the ultimate goal of determining the feasibility of III-nitride transistors grown by NH3-MOMBE.

Heterostructures of the materials system GaN/AlGaN/GaN were grown by molecular beam epitaxy on 6H-SiC substrates and high electron mobility transistors (HEMTs) were fabricated. For devices with large gate periphery an air bridge technology was developed for the drain contacts of the finger structure. The devices showed DC drain currents of more than 1 A/mm and values of the transconductance between 120 and 140 mS/mm. A power added efficiency of 41 % was measured on devices with a gate length of 1 µm at 2 GHz and 45 V drain bias. Power values of 8 W/mm were obtained. Devices with submicron gates exhibited power values of 6.1 W/mm (7 GHz) and 3.16 W/mm (25 GHz) respectively. The rf dispersion of the drain current is very low, although the devices were not passivated. / Heterostrukturen im Materialsystem GaN/AlGaN/GaN wurden mittels Molekularstrahlepitaxie auf 6H-SiC-Substraten gewachsen und High-Electron-Mobility-Transistoren (HEMTs) daraus hergestellt. Für Bauelemente mit großer Gateperipherie wurde eine Air-Bridge-Technik entwickelt, um die Drainkontakte der Fingerstruktur zu verbinden. Die Bauelemente zeigten Drainströme von mehr als 1 A/mm und Steilheiten zwischen 120 und 140 mS/mm. An Transistoren mit Gatelängen von 1 µm konnten Leistungswirkungsgrade (Power Added Efficiency) von 41 % (bei 2 GHz und 45 V Drain-Source-Spannung) sowie eine Leistung von 8 W/mm erzielt werden. Bauelemente mit Gatelängen im Submikrometerbereich zeigten Leistungswerte von 6,1 W/mm (7 GHz) bzw. 3,16 W/mm (25 GHz). Die Drainstromdispersion ist sehr gering, obwohl die Bauelemente nicht passiviert wurden.

Neste trabalho estudamos as estruturas e as mobilidades eletrônicas em um sistema quase-bidimensional de poços quânticos parabólicos de AlxGa1-xAs dopados. Obtemos as auto-energias, as funções de onda e os perfis dos potencias de confinamento efetivo no sistema, através das soluções numéricas das equações de Schrödinger e de Poisson de forma autoconsistente. Em particular, estudamos as mobilidades quânticas e de transporte nestes sistemas. Devido a ocupação de várias subbandas nestes sistemas, as contribuições dos espalhamentos inter-subbandas para as mobilidades têm a mesma importância que os espalhamentos intra-subbandas. Obtemos as mobilidades de cada subbanda devido aos espalhamentos por impurezas doadoras e aceitadoras ionizadas e por potencial de liga. Analisamos os efeitos das distribuições de doadores dopados, de aceitadores de fundo e do potencial de gate externo / In this work we study the electronic structure and electron mobilities in doped wide parabolic quantum wells of AlxGa1-xAs. The subband energies, the wavefunctions, and the effective confining potential profile are obtained by studying selfconsistently the coupled Schrödinger and Poisson equations. Based on the numerical results of the electronic structure, we calculate the quantum and transport mobilities of the system. Usually several subbands are occupied in such systems and they are strongly coupled to each other, the intersubband interaction shows the same importance as the intrasubband one to the electronic transport. We study and analyze the electron mobility of each subband due to the ionized donor scattering and the alloy scattering. We also show the effect of ionized background acceptor impurity scattering

Les travaux présentés dans ce manuscrit sont axés sur le développement et la caractérisation de modules technologiques sur semiconducteurs à large bande interdite à base de nitrure de gallium (GaN), pour la réalisation de transistors et de cathodes froides. Ils ont été réalisés au sein du laboratoire III-V lab, commun aux entités : Alcatel - Thales - CEA Leti. Notre projet de recherche a bénéficié d'un soutien financier assuré par Thales Electron Devices (TED) et l'Agence Nationale de la Recherche ( ANR ). Concernant les transistors HEMT III-N, nos investigations se sont focalisées sur le développement des parties actives des transistors, incluant principalement la structuration des électrodes de grilles, l'étude de la passivation des grilles métalliques, ainsi que l'étude de diélectriques de grille pour la réalisation de structures MIS-HEMT.Les transistors MOS-HEMT « Normally-off » réalisés présentent des performances comparables à l'état de l'art, avec une densité de courant de drain maximum comprise entre 270 mA et 400 mA / mm, un ratio ION / IOFF > 1100, et des tensions de claquage > 200V. Les tensions de seuil sont comprises entre + 1,8 V et + 4 V. Nos contributions au développement des cathodes froides ont permis de démontrer une première émission dans le vide à partir de cathodes GaN, avec une densité de courant maximale de 300 µA / cm2 pour une tension de polarisation de 40 V / The results presented in this manuscript relate to technological developments and device processing on wide bandgap III-N semiconductor materials. They have been focused on III-N HEMT transistors and GaN cold cathodes. They have been realised within the III-V lab, which is a common entity between: Alcatel - Thales - CEA Leti. They have been financially supported by Thales Electron Devices company (TED) and the French National Research Agency ( ANR ). Regarding III-N HEMTs, our investigations have been focused on the development of device gate processing, which includes : the structuration of gate electrodes, the study of device passivation, and the realization of Metal-Insulator-Semiconductor High Mobility Electron Transistors ( MIS-HEMTs ). The “ Normally-off ” MOS-HEMT structures we have realized exhibit performances comparable to the state of the art, with a maximum drain current density between 270 and 400 mA / mm, a ION / IOFF ratio > 1.100, and a breakdown voltage > 200V. The threshold voltage values range between + 1,8 V and + 4V. We have also been able to demonstrate prototype GaN cold cathodes providing a maximum current density of 300 µA / cm2, emitted in vacuum for a bias voltage around 40 V

The Square Kilometre Array (SKA) is a multibillion and a multinational science project to build the world’s largest and most sensitive radio telescope. For a very large field of view, the combined collecting area would be one square kilometre (or 1, 000, 000 square metre) and spread over more than 3,000 km wide which will require a massive count of antennas (thousands). Each of the antennas contains hundreds of low noise amplifier (LNA) circuits. The antenna arrays are divided into low, medium and high operational frequencies and located at different positions to boost up the telescope’s scanning sensitivity.The objective of this work was to develop and fabricate fully on-chip LNA circuits to meet the stringent requirements for the mid-frequency array from 0.4 GHz to 1.4 GHz of the SKA radio astronomy telescope using Monolithic Microwave Integrated Circuit technology (MMIC). Due to the number of LNA reaching figures of millions, the fabricated circuits were designed with the consideration for low cost fabrication and high reliability in the receiver chain. Therefore, a relaxed optical lithography with Lg = 1 µm was adopted for a high yield fabrication process.Towards the fulfilment of the device’s low noise characteristics, a large number of device designs, fabrication and characterisation of InGaAs/InAlAs/InP pHEMTs were undertaken. These include optimisations at each critical fabrication steps. The device’s high breakdown and very low gate leakage characteristics were further improved by a combination of judicious epitaxial growth and manipulation of materials’ energy gaps. An attempt to increase the device breakdown voltage was also employed by incorporating Field Plate structure at the gate terminal. This yielded the devices with improvements in the breakdown voltage up to 15 V and very low gate leakage of 1 µA/mm, in addition to high transconductance (gm) characteristic. Fully integrated double stage LNA had measured NF varying from 1.2 dB to 1.6 dB from 0.4 GHz to 1.4 GHz, compared with a slightly lower NF obtained from simulation (0.8 dB to 1.1 dB) across the same frequency band.These are amongst the attractive device properties for the implementation of a fully on-chip MMIC LNA circuits demonstrated in this work. The lower circuit’s low noise characteristic has been demonstrated using large gate width geometry pHEMTs, where the system’s noise resistance (Rn) has successfully reduced to a few ohms. The work reported here should facilitate the successful implementation of rugged low noise amplifiers as required by SKA receivers.

Il y a actuellement un intérêt croissant pour la construction des dispositifs électroniques à semiconducteur pour les applications domotiques. La technologie des semiconducteurs de puissance a été essentiellement limitée au silicium. Récemment, de nouveaux matériaux ayant des propriétés supérieures sont étudiés en tant que remplaçants potentiels, en particulier : le nitrure de gallium et le carbure de silicium. L'état actuel de développement de la technologie 4H-SiC est beaucoup plus mature que pour le GaN. Cependant, l'utilisation de 4H-SiC n’est pas une solution économiquement rentable pour la réalisation des redresseurs Schottky 600 V. Les progrès récents dans le développement des couches épitaxiées de GaN de type n sur substrat Si offrent de nouvelles perspectives pour le développement des dispositifs de puissance à faible coût. C’est dans ce cadre que ma thèse s’inscrit pour réaliser avec ce type de substrat, un redresseur Schottky de puissance avec un calibre en tension de l’ordre de 600V. Deux architectures de redresseurs sont exposées. La première est une architecture pseudo-verticale proposée dans le cadre du projet G2ReC et la deuxième est une architecture latérale à base d’hétérojonction AlGaN/GaN obtenue à partir d'une structure de transistor HEMT. L’optimisation de ces deux dispositifs en GaN est issue de simulation par la méthode des éléments finis. Dans ce cadre, une adaptation des modèles de simulation à partir des paramètres physiques du GaN extraits depuis la littérature a été effectuée. Ensuite, une étude d’influence des paramètres géométriques et technologiques sur les propriétés statiques en direct et en inverse des redresseurs a été réalisée. Enfin, des structures de tests ont été fabriquées et caractérisées afin d’évaluer et d’optimiser le caractère prédictif des simulations par éléments finis. Ces études nous ont conduit à identifier l'origine des limites des structures de première génération et de définir de nouvelles structures plus performantes. / There is increasing interest in the fabrication of power semiconductor devices in home automation applications. Power semiconductor technology has been essentially confined to Si. Recently, new materials with superior properties are being investigated as potential replacements, in particular silicon carbide (SiC) and gallium nitride (GaN). The current state of development of SiC technology is much more mature than for GaN. However, the use of 4H-SiC is not a cost effective solution for realizing a medium and high voltage Schottky diode. Recent advances on the development of thick n-type GaN epilayers on Si substrate offer new prospects for the development of a low-cost Schottky rectifiers for at least medium voltage range 600 V. In the context of our thesis, two types of GaN based rectifier architectures have been studied. The first one is a pseudo-vertical architecture proposed during previous G2ReC project. The second one has a lateral structure with AlGaN/GaN heterojunction, derived from a HEMT structure. The optimization of the Schottky rectifiers has been achieved by finite element simulations. As a first step, the models are implemented in the software and adjusted with the parameters described in the literature. The influence of the geometrical and physical parameters on the specific on-resistance and on the breakdown voltage has been analysed. Finally, the test devices have been realized and characterized to optimize and to validate the parameters of these models. These studies lead to identify the limits of the structures and create a new generation of powerful structures.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The main focus of this thesis is to document the formulation, extraction and validation of nonlinear models for the on-wafer gallium nitride (GaN) high-electron mobility (HEMT) devices manufactured at the Interuniversity Microelectronics Centre (IMEC) in Leuven, Belgium. GaN semiconductor technology is fast emerging and it is expected that these devices will play an important role in RF and microwave power amplifier applications. One of the main advantages of the new GaN semiconductor technology is that it combines a very wide band-gap with high electron mobility, which amounts to higher levels of gain at very high frequencies. HEMT devices based on GaN, is a fairly new technology and not many nonlinear models have been proposed in literature. This thesis details the design of hardware and software used in the development of the nonlinear models. An intermodulation distortion (IMD) measurement setup was developed to measure the second and higher-order derivative of the nonlinear drain current. The derivatives are extracted directly from measurements and are required to improve the nonlinear model IMD predictions. Nonlinear model extraction software was developed to automate the modelling process, which was fundamental in the nonlinear model investigation. The models are implemented in Agilent’s Advanced Design System (ADS) and it is shown that the models are capable of accurately predicting the measured S-parameters, large-signal singletone and two-tone behaviour of the GaN devices. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie tesis is om die formulering, ontrekking en validasie van nie-lineêre modelle vir onverpakte gallium nitraat (GaN) hoë-elektronmobilisering transistors (HEMTs) te dokumenteer. Die transistors is vervaaardig by die Interuniversity Microelectronics Centre (IMEC) in Leuven, België. GaN-halfgeleier tegnologie is besig om vinnig veld te wen en daar word voorspel dat hierdie transistors ʼn belangrike rol gaan speel in RF en mikrogolf kragversterker toepassings. Een van die hoof voordele van die nuwe GaN-halfgeleier tegnologie is dat dit 'n baie wyd band-gaping het met hoë-elektronmobilisering, wat lei tot hoë aanwins by mikrogolf frekwensies. GaN HEMTs is 'n redelik nuwe tegnologie en nie baie nie-lineêre modelle is al voorgestel in literatuur nie. Hierdie tesis ondersoek die ontwerp van die hardeware en sagteware soos gebruik in die ontwikkeling van nie-lineêre modelle. 'n Intermodulasie distorsie-opstelling (IMD-opstelling) is ontwikkel vir die meting van die tweede en hoër orde afgeleides van die nie-lineêre stroom. Die afgeleides is direk uit die metings onttrek en moet die nie-lineêre IMD-voorspellings te verbeter. Nie-lineêre onttrekking sagteware is ontwikkel om die modellerings proses te outomatiseer. Die modelle word geïmplementeer in Agilent se Advanced Design System (ADS) en bewys dat die modelle in staat is om akkurate afgemete S-parameters, grootsein enkeltoon en tweetoon gedrag van die GaN-transistors te kan voorspel.