Investigation of epitaxial lift-off GaAs and langmuir-blodgett films for optoelectronic device applications

Epitaxial lift-off (ELO), a technique of removing an epitaxially grown GaAs layer from its growth substrate by selective etching of an AlAs sacrificial layer, is described for field-effect transistor fabrication independent of the GaAs growth substrate. Metal Semiconductor Field-Effect Transistors (MESFETs) and High Electron Mobility Transistors (HEMTs) fabricated on silicon and sapphire substrates using ELO are investigated. A 0.1 μm gate length depletion mode MESFET made on silicon exhibited a unity current gain frequency ft = 34 GHz. Excellent device isolation with subpicoampere leakage currents is obtained. A high input impedance amplifier has been implemented on silicon substrate using ELO GaAs MESFETs. The amplifier had an input RC time constant limited bandwidth of 500 MHz. Results of investigation of a novel source of cadmium and zinc diffusion for shallow p+-n junction fabrication in In0.53Ga0.47As/InP are also presented. Langmuir-Blodgett (LB) deposited monolayers of Cadmium and Zinc arachidate have been used as a source of Cd and Zn dopants in InGaAs/InP. This new source provides precise control of the dopant dose through the number of LB film monolayers deposited and it is also a safer method of handling toxic Cd. The LB film can be patterned by lift-off for a patterned diffusion without a mask. Highly doped (Na= 2 -4 x 1019 cm-3 ), shallow (0.1-0.4 μm) p+-n junctions have been obtained. Junction field-effect transistors(JFETs) and PIN photodetectors have been fabricated as a demonstration of the usefulness of the technique. A PIN photodetector had a 100 pA dark current at -5 V DC bias and a bandwidth of 2 GHz. A new technique for fabricating optoelectronic integrated circuit (OEIC) photoreceivers for 1.3-1.55 μm wavelength optical communication has also been proposed. The proposed OEIC uses ELO GaAs MESFETs and InGaAs/InP PIN photodetectors

Extreme Temperature Switch Mode Power Supply Based on Vee-square Control Using Silicon Carbide, Silicon on Sapphire, Hybrid Technology

Switch mode power supplies, commonly known as SMPS are basic building blocks of the electronic systems. SMPS performs power regulation by accepting a raw input voltage and transforming it to required voltage at output with desired characteristics. Electronic systems used in applications such as deep well oil drilling, geothermal wells and deep space explorations is expected to operate under extremely harsh conditions like elevated temperature, high pressure and radiation prone environments. To support the onboard electronics in these applications, SMPS capable of operating at extreme temperatures are of high interest.This research work deals with the design and development of a switch mode power supply capable of operating over the temperature range of 300 degree centigrade (�C). Silicon carbide field effect transistors are used as power devices in the design to tolerate these extreme high ambient temperatures without compromising power handling capability. The simplest yet robust vee square control architecture is adopted for control mechanism. The control electronics are implemented as an integrated circuit in 0.5 �m silicon on sapphire process. The supporting components like high temperature tolerant inductors and capacitors are identified by evaluating various samples at elevated temperature. This is the first demonstration of SMPS capable of operating at 275�C as a standalone component. Also for the first time, a gate drive mechanism based on planar transformer architecture is studied and presented for high temperature operation. A low cost packaging technique suited for harsh environment operation is proposed based on gold on aluminum nitride thin film technology. The basic analog building blocks of the system, such as comparator, voltage reference and rail-to-rail amplifiers are made available in discrete packages for use at temperatures above 275�C. A SMPS prototype on a 1.8 square inches substrate is developed and tested. Test results indicate that the system is capable of operating continuously at 275�C for extended period of time, providing the desired performance characteristics.School of Electrical & Computer Engineerin

Proceedings of the Cold Electronics Workshop

The benefits and problems of the use of cold semiconductor electronics and the research and development effort required to bring cold electronics into more widespread use were examined

Infrared receivers for low background astronomy: Incoherent detectors and coherent devices from one micrometer to one millimeter

The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices

Materials Development for Gallium Nitride Power Devices

Gallium Nitride has gained prominence in the field of power electronics due to its high bandgap, high critical electric field, high mobility and high saturation-drift velocity. This means that GaN can be used to make devices that have a low on-resistance along with a high breakdown voltage. High frequency GaN HEMTs have been commercially available since 2006 and still being improved. The high power market is just starting to tap into GaN devices. Vertical transistors are especially attractive for high power applications, as they provide the possibility of a high breakdown voltage at a low chip size, thus, a low cost price. In addition to this, GaN devices can also use the two-dimensional electron gas formed at the GaN/AlGaN heterojunction to obtain a higher current.Several GaN based power devices are being investigated - both vertical and lateral. Our group has been focusing on the Oxide GaN-interlayer Field Effect Transistor (OGFET) and the Current Aperture Vertical Electron Transistor (CAVET). On the lateral side, power HEMTs are being developed. This work focuses on materials development for the various types of power devices. A primary motive for this thesis is for it to serve as a reference manual for researchers working on GaN power devices. Vertical power devices are united by a common feature – a thick drift region with a low n-type carrier concentration. Through simulations, it has been shown that the optimal carrier concentration to simultaneously achieve a low Ron and a high breakdown voltage is about 1 x 1016 cm-3. Through our experiments, it was demonstrated that it is also the carrier concentration range where the electron mobility peaks. Achieving such a low doping can be problematic as it is in the range of impurity dopants such as Carbon and Oxygen. A low doping and record mobility was achieved for vertical devices by MOCVD and applied to the OGFET and the CAVET. Devices were grown both, on sapphire and on bulk GaN and high breakdown voltages were achieved.Power devices require an elaborate growth and fabrication process, including regrowth on p-GaN doped by Magnesium and regrowth within trenches. Magnesium is known to diffuse into subsequent layers during regrowth, lowering device performance. A novel approach to circumvent this issue is presented, which can eliminate the need to remove the sample from the MOCVD chamber altogether. A low temperature GaN layer grown via flow modulation epitaxy successfully suppressed the Mg penetration at a rate of 5 nm/dec, the lowest ever by MOCVD, leading to the formation of an abrupt p-GaN:Mg/GaN junction.Regrowth within trenches was optimized for different applications. GaN was grown conformally within narrow trenches by exploring various growth conditions. A complete filling of trench was also achieved for a different set of applications. Finally, conformal regrowth of high composition, low temperature AlGaN was optimized for deep-recessed gate HEMTs to lower gate leakage. All of these were planar regrowths and no masks were used

Circuits Techniques for Wireless Sensing Systems in High-Temperature Environments

RÉSUMÉ Dans ce projet, nous proposons de nouvelles techniques d’intégration basées sur la technologie de nitrure de gallium (GaN). Ces techniques permettent de mettre en œuvre un système de transmission de données sans fil entièrement intégré dédié aux capteurs de surveillance pour des applications d'environnement hostile. Le travail nécessite de trouver une technologie capable de résister à l'environnement sévère, principalement à haute température, et de permettre un niveau d'intégration élevé. Le système réalisé serait le premier dispositif de transmission de données basé sur la technologie GaN. En plus de supporter les conditions de haute température (HT) dépassant 600 oC, le système de transmission sans fil attendu devrait fonctionner à travers une barrière métallique séparant le module émetteur du récepteur. Une revue de la littérature sur les applications en environnements hostiles ainsi que sur l'électronique correspondante a été réalisée pour sélectionner la technologie AlGaN/GaN HEMT (transistor à haute mobilité d'électrons) comme une technologie appropriée. Le kit de conception GaN500, fourni par le Conseil national de recherches du Canada (CNRC), a été adopté pour concevoir et mettre en œuvre le système proposé. Cette technologie a été initialement introduite pour desservir les applications radiofréquences (RF) et micro-ondes. Par conséquent, elle n'avait pas été validée pour concevoir et fabriquer des circuits intégrés analogiques et numériques complexes et son utilisation à des températures extrêmes n’était pas validée. Nous avons donc caractérisé à haute température des dispositifs fabriqués en GaN500 et des éléments passifs intégrés correspondants ont été réalisés. Ces composants ont été testés sur la plage de température comprise entre 25 et 600 oC dans cette thèse. Les résultats de caractérisation ont été utilisés pour extraire les modèles HT des HEMT intégrés et des éléments passifs à utiliser dans les simulations. En outre, plusieurs composants intégrés basés sur la technologie GaN500, notamment des NOT, NOR, NAND, XOR, XNOR, registres, éléments de délais et oscillateurs ont été mis en œuvre et testés en HT. Des circuits analogiques à base de GaN500, comprenant un amplificateur de tension, un comparateur, un redresseur simple alternance, un redresseur double alternance, une pompe de charge et une référence de tension ont également été mis en œuvre et testés en HT. Le système de transmission de données mis en œuvre se compose d'un module de modulation situé dans la partie émettrice et d'un module de démodulation situé dans la partie réceptrice.----------ABSTRACT In this project, we propose new integrated-circuit design techniques based on the Gallium Nitride (GaN) technology to implement a fully-integrated data transmission system dedicated to wireless sensing in harsh environment applications. The goal in this thesis is to find a proper technology able to withstand harsh-environments (HEs), mainly characterized by high temperatures, and to allow a high-integration level. The reported design is the first data transmission system based on GaN technology. In addition to high temperature (HT) environment exceeding 600 oC, the expected wireless transmission systems may need to operate through metallic barriers separating the transmitting from the receiving modules. A wide literature review on the HE applications and corresponding electronics has been done to select the AlGaN/GaN HEMT (high-electron-mobility transistor) technology. The GaN500 design kit, provided by National Research Council of Canada (NRC), was adopted to design and implement the proposed system. This technology was initially provided to serve radio frequency (RF) and microwave circuits and applications. Consequently, it was not validated to implement complex integrated systems and to withstand extreme temperatures. Therefore, the high-temperature characterization of fabricated GaN500 devices and corresponding integrated passive elements was performed over the temperature range 25-600 oC in this thesis. The characterization results were used to extract HT models of the integrated HEMTs and passive elements to be used in simulations. Also, several GaN500-based digital circuits including NOT, NOR, NAND, XOR, XNOR, register, Delay and Ring oscillator were implemented and tested at HT. GaN500-based Analog circuits including front-end amplifier, comparator, half-bridge rectifier, full-bridge rectifier, charge pump and voltage reference were implemented and tested at HT as well. The implemented data transmission system consists of a modulation module located in the transmitting part and a demodulation block located in the receiving part. The proposed modulation system is based on the delta-sigma modulation technique and composed of a front-end amplifier, a comparator, a register, a charge pump and a ring oscillator. The output stage of the transmitter is intended to perform the load-shift-keying (LSK) modulation required to accomplish the data transmission through the dedicated inductive link. At the receiver level, three demodulation topologies were proposed to acquire the delivered LSK-modulated signals

Contributions to the design of power modules for electric and hybrid vehicles: trends, design aspects and simulation techniques

314 p.En la última década, la protección del medio ambiente y el uso alternativo de energías renovables están tomando mayor relevancia tanto en el ámbito social y político, como científico. El sector del transporte es uno de los principales causantes de los gases de efecto invernadero y la polución existente, contribuyendo con hasta el 27 % de las emisiones a nivel global. En este contexto desfavorable, la electrificación de los vehículos de carretera se convierte en un factor crucial. Para ello, la transición de la actual flota de vehículos de carretera debe ser progresiva forzando la investigación y desarrollo de nuevos conceptos a la hora de producir vehículos eléctricos (EV) y vehículos eléctricos híbridos (HEV) más eficientes, fiables, seguros y de menor coste. En consecuencia, para el desarrollo y mejora de los convertidores de potencia de los HEV/EV, este trabajo abarca los siguientes aspectos tecnológicos: - Arquitecturas de la etapa de conversión de potencia. Las principales topologías que pueden ser implementadas en el tren de potencia para HEV/EV son descritas y analizadas, teniendo en cuenta las alternativas que mejor se adaptan a los requisitos técnicos que demandan este tipo de aplicaciones. De dicha exposición se identifican los elementos constituyentes fundamentales de los convertidores de potencia que forman parte del tren de tracción para automoción.- Nuevos dispositivos semiconductores de potencia. Los nuevos objetivos y retos tecnológicos solo pueden lograrse mediante el uso de nuevos materiales. Los semiconductores Wide bandgap (WBG), especialmente los dispositivos electrónicos de potencia basados en nitruro de galio (GaN) y carburo de silicio (SiC), son las alternativas más prometedoras al silicio (Si) debido a las mejores prestaciones que poseen dichos materiales, lo que permite mejorar la conductividad térmica, aumentar las frecuencias de conmutación y reducir las pérdidas.- Análisis de técnicas de rutado, conexionado y ensamblado de módulos de potencia. Los módulos de potencia fabricados con dies en lugar de dispositivos discretos son la opción preferida por los fabricantes para lograr las especificaciones indicadas por la industria de la automoción. Teniendo en cuenta los estrictos requisitos de eficiencia, fiabilidad y coste es necesario revisar y plantear nuevos layouts de las etapas de conversión de potencia, así como esquemas y técnicas de paralelización de los circuitos, centrándose en las tecnologías disponibles.Teniendo en cuenta dichos aspectos, la presente investigación evalúa las alternativas de semiconductores de potencia que pueden ser implementadas en aplicaciones HEV/EV, así como su conexionado para la obtención de las densidades de potencia requeridas, centrándose en la técnica de paralelización de semiconductores. Debido a la falta de información tanto científica como comercial e industrial sobre dicha técnica, una de las principales contribuciones del presente trabajo ha sido la propuesta y verificación de una serie de criterios de diseño para el diseño de módulos de potencia. Finalmente, los resultados que se han extraído de los circuitos de potencia propuestos demuestran la utilidad de dichos criterios de diseño, obteniendo circuitos con bajas impedancias parásitas y equilibrados eléctrica y térmicamente. A nivel industrial, el conocimiento expuesto en la presente tesis permite reducir los tiempos de diseño a la hora de obtener prototipos de ciertas garantías, permitiendo comenzar la fase de prototipado habiéndose realizado comprobaciones eléctricas y térmicas