The objective of this research is to demonstrate the feasibility of the implementation of low-cost, small-size, and high power RF front ends using CMOS technology which has been known not to be suitable for high-power applications due to its material characteristic. One part of this research focuses on developing GaAs switches for multi band and multi mode high power applications. The development of RF front end switches for high power applications using CMOS technology is very challenging in that the characteristics of CMOS technology such as low breakdown voltages, slow electron mobility and existence of substrate junction diodes are limiting power handling capability of CMOS technology. Various topologies of CMOS switches have been employed in implementing high power RF front end CMOS switches in order to overcome material limitations of CMOS technology in high power applications. Based on measurement data such as power handling capability and S-parameters of fabricated CMOS switches, the feasibility of use of CMOS technology in high power RF antenna switch design has been studied, and novel methods of designing CMOS switches to improve the power handling capability without compensating S-parameter performance are proposed. As a part of this research, multi-band and multi-mode power switches using GaAs technology are fabricated and tested for use of the commercial applications such as handsets covering GSM, PCS/DCS, and UMTS bands. Current commercial RF switch products demand small size, low cost and low voltage control as the number of wireless standards integrated in a single application increases. This research provides a solution for commercial products which can meet all the specifications as well as needs required in the wireless market.

The objective of this work was to study the noise in semiconductors and relate the transport mechanisms in the devices with the noise from the devices. The main part of the work was to set up a system for the measurement of noise in semiconductor devices. To establish the sensitivity of the system, it was calibrated at different temperatures. Some of the results from GaAs pn-junction showed some anomaly from that available in the literature. But certain points are yet to be clarified. This requires certain developments in the measurement system. In the case of QWIPS structures, studies on some samples with varying number of wells are required and in order to study the GR noise spectra and other activated processes, we need to study the temperature dependence of the noise and a larger bias variation for studying the low frequency current noise.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 87-94). Also available in electronic format on the Internet.

Since a decade, spintronics and related physics have attracted considerable attention due to the massive research conducted in these areas. The main reason for growing interest in these fields is the expectation to use the electrons spin instead of or in addition to the charge for the applications in spin-based electronics, quantum information, and quantum computation. A prime concern for these spins to be possible candidates for carrying information is the ability to coherently control them on the time scales much faster than the decoherence times. This thesis reports on the spin dynamics in two-dimensional electron gases hosted in artificially grown III-V semiconductor quantum wells. Here we present a series of experiments utilizing the techniques to optically control the spin polarization triggered by either optical or electrical methods i.e. well known pump-probe technique and current-induced spin polarization. We investigated the spin coherence in high mobility dense two-dimensional electron gas confined in GaAs/AlGaAs double and triple quantum wells, and, it\'s dephasing on the experimental parameters like applied magnetic field, optical power, pump-probe delay and excitation wavelength. We have also studied the large spin relaxation anisotropy and the influence of sample temperature on the long-lived spin coherence in triple quantum well structure. The anisotropy was studied as a function sample temperature, pump-probe delay time, and excitation power, where, the coherent spin dynamics was measured in a broad range of temperature from 5 K up to 250 K using time-resolved Kerr rotation and resonant spin amplification. Additionally, the influence of Al concentration on the spin dynamics of AlGaAs/AlAs QWs was studied. Where, the composition engineering in the studied structures allows tuning of the spin dephasing time and electron g-factor. Finally, we studied the macroscopic transverse drift of long current-induced spin coherence using non-local Kerr rotation measurements, based on the optical resonant amplification of the electrically-induced polarization. Significant spatial variation of the electron g-factor and the coherence times in the nanosecond scale transported away half-millimeter distances in a direction transverse to the applied electric field was observed. / Há uma década, a spintrônica e outras áreas relacionadas vêm atraindo considerável atenção, devido a enorme quantidade de pesquisa conduzidas por elas. A principal razão para o crescente interesse neste campo é a expectativa da aplicação do controle do spin do elétron no lugar ou em adição à carga, em dispositivos eletrônicos e informação e computação quânticas. A possibilidade destes spins carregarem informação depende, primeiramente, da habilidade de controlá-los coerentemente, em uma escala de tempo muito mais rápida do que o tempo de decoerência. Esta tese trata da dinâmica de spins em gases de elétrons bidimensionais, em poços quânticos de semicondutores III-V, crescidos artificialmente. Nós apresentamos uma série de experimentos, utilizando técnicas para o controle ótico da polarização de spin, desencadeadas por métodos óticos ou eletrônicos, ou seja, técnicas conhecidas de bombeio e prova e polarização de spin induzida por corrente. Nós investigamos a coerência de spin em gases bidimensionais, confinados em poços quânticos duplos e triplos de GaAs/AlGaAs e a dependência da defasagem com parâmetros experimentais, como campo magnético externo, potência ótica, tempo entre os pulsos de bombeio e prova e comprimento de onda da excitação. Também estudamos a grande anisotropia de relaxação de spin como função da temperatura da amostra, potência de excitação e defasagem entre bombeio e prova, medidos para uma vasta gama de temperatura, entre 5K e 250K, usando Rotação de Kerr com Resolução Temporal (TRKR) e Amplificação Ressonante de Spin (RSA). Além disso estudamos a influência da concentração de Al na dinâmica dos poços de AlGaAs/AlAs, para o qual a engenharia da composição da estrutura permite sintonizar o tempo de defasagem de spin e o fator $ g $ do elétron. Por fim, estudamos a deriva transversal macroscópica da longa coerência de spin induzida por corrente, através de medidas de Rotação de Kerr não-locais, baseadas na amplificação ressonante ótica da polarização eletricamente induzida. Observamos uma variação espacial significante do fator $ g $ e do tempo de vida da coerência, na escala de nanosegundos, deslocada distâncias de meio milímetro na direção transversa ao campo magnético aplicado.

É feito um resumo dos principais modelos criados para se explicar as intrigantes propriedades do centro DX e atualizar o problema. O decaimento da fotocondutividade persistente (PPC) é medido em AlxGa1-x As dopado com Si e se discute a validade dos modelos em função da cinética de captura dos elétrons pelos centros DX. Boa concordância com o modelo de Chadi e Chang é encontrada desde que se postule a existência de um nível doador mais raso. O crescimento por MBE assim como todo o processamento de amostras para os experimentos realizados é descrito sinteticamente. É discutido também o problema dos contatos a baixa temperatura e a possível influência dos centros DX nos desvios do comportamento ôhmico observados. Inclui-se também a descoberta da. fotocondutividade persistente em AlxGa1-xAs dopado com Pb, que também é relacionado à existência dos centros DX. / A short discussion about the main models created to explain the striking properties of the DX center is done in order to bring the problem up-to-date. The decay of persistent photoconductivity is measured and it is analyzed as a function of the kinetics of electron trapping by DX centers in Si-doped AlxGa1-xAs, according to these models. Good agreement with Chadi and Chang\'s model is found as long as we postulate the existence of a shallower donor. The M.B.E. growth as well as the whole sample processing is shortly described. It in siso diacussed the problem of low temperature contacts and the possible influence of DX centers in the deviation from ohmic behavior. Persistent Photoconductivity has been found in Pb-doped AlxGa1-xAs and it is also related to the DX center existence.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / An experimental synovitis model of the radio-carpal joint was induced in 8 male intact ponies with an intra-articular injection of 0.25ml of Freund s complete adjuvant. Four ponies had the affected joint irradiated with a 4J/cm2 of laser in a cranio-caudal direction. The control group received the same technique with the device turned off. The heart rate was lower (p<0.05) in the treated group (37±6.9) than in the control group (41.2±5.7). The carpal angle of maximum flexion was significantly (p <0.05) lower in the treated group (94.4±27.2) than in the control group (125.6±5.3). The results of this study show that treatment with laser of gallium arsenide, in the dose of 4J/cm2, presented analgesic effect and improved joint movement in this model of Freund s adjuvant induced acute synovitis. / Um modelo experimental de sinovite aguda rádio-carpiana foi induzido em oito pôneis machos adultos com uma injeção intra-articular de 0,25 ml de adjuvante completo de Freund para avaliar o efeito da terapia laser nesta lesão. Um grupo (n= 4) teve a articulação afetada tratada com laser de arseneto de gálio na dose diária de 4J/cm2 na incidência crânio-caudal por 15 sessões. O grupo controle (n= 4) não foi tratado. A freqüência cardíaca foi estatisticamente (p<0,05) menor no grupo tratado (37±6,9) do que no grupo controle (41,2±5,7). O ângulo de flexão carpal máximo foi significativamente (p<0,05) menor no grupo tratado (94,4±27,2) do que no grupo controle (125,6±5,3). Os resultados deste estudo mostram que a terapia com laser de arseneto de gálio na dose de 4J/cm2 apresentou efeito analgésico e melhorou a mobilidade do membro afetado pela sinovite aguda induzida por Adjuvante Completo de Freund.

Cette thèse porte sur l'élaboration d'un biocapteur, à bas coût, pour la détection de pathogènes dans les secteurs de l'agroalimentaire et de l'environnement. Le modèle visé est la bactérie Escherichia coli, dont les souches pathogènes sont responsables, chaque année, de plusieurs crises sanitaires. L'utilisation de biocapteurs pour une détection rapide, sensible et sélective de pathogènes répond ainsi aux inquiétudes quant aux risques d'infection pour la population. Le capteur est constitué d'une fine membrane en arsénieure de gallium (GaAs) vibrant sur des modes de cisaillement d'épaisseur générés par champ électrique latéral via ses propriétés piézoélectriques. Nous montrons dans ce travail que la GaAs offre des possibilités de microfabrication, de biofonctionnalisation et de régénération intéressantes pour la conception d'un dispositif à bas coût. Nous avons mis en parallèle deux méthodes d'usinage de membranes minces : par voie chimique et par plasma, avec pour objectif, l'obtention de structures planes et lisse. Nous nous sommes intéressés à la réalisation d'une interface de bioreconnaissance. La caractérisation de celle-ci, par les techniques de spectroscope infrarouge à transformée de Fourier, nous a fait progresser sur a compréhension du phénomène d'auto-assemblage de molécules sur GaAs et nous a permis de développer des interfaces à haute densité. Nous avons étudié sa régénération et la photo-oxydation par UV a démontré un fort potentiel pour des applications de capteurs réutilisables. Enfin à travers des caractérisations électriques du transducteur, nous avons mis en avant l'impact de différents paramètres de l'environnement sur la réponse du dispositif. / This thesis addresses the development of a potentially low cost sensor dedicated for detection of pathogens in food industry processing and environment sectors. Such a sensor could serve detection of Escherichia coli bacteria whose pathogenic strains are the source of foodborne illnesses encountered worldwide every year. Hence, biosensor devices are needed for a rapid, sensitive and selective detection of pathogens to prevent outbreak risks. The design of the sensor consists of a resonant membrane fabricated in gallium arsenide (GaAs) crystal that operates at shear modes of bulk acoustic waves generated by lateral field excitation. In addition to its piezoelectric properties, as shown in this work, fabrication of a GaAs-based biosensor benefits from a well-developed technology of microfabrication and biofunctionalization and the possibility of regeneration that should result in cost savings of used devices. The transducer was fabricated by using typical clean room fabrication techniques. Plasma and wet etching were investigated and compared for achieving thin membranes with high quality surface morphology. Extensive research was carried out by Fourier transform infrared spectroscopy to determine optimum conditions for biofunctionalization of the GaAs surface. This activity allowed to advance the fundamental knowledge of self-assembly formation and, consequently, fabrication of high density biointerfaces. Among different biochip regeneration methods, it has been demonstrated that liquid UV photooxidation has a great potential for re-usable devices. Finally, operation of the transducer device was evaluated in various medium, simulating real conditions for detection.

High quality and accurate computational data was obtained through first principle quantum mechanical calculations originated from density functional theory without the inclusion of empirical data (ab initio). The support of the computing facility NGS allows us to carry out our research involving large scale atomistic simulations. The data we recently obtained clearly shows piezoelectricity in GaAs and InAs are proved to be non linear in relation to a general strain.The high order fitting equation obtained through the parameterization procedure allowed us to directly evaluate higher order piezoelectric coefficients. By comparing with other linear and non linear models and also experimental data, we reached the conclusion that the validity of our model is correct in the limitation of small shear strain, particularly in case of (111) grown semiconductors. Such limitation however is not restricted under pseudomorphic growth in (001) direction where typically shear strain is small.We further validate our model through elasticity theory to demonstrate the sign of the polarization is found to be opposite to bulk values for an InAs semiconductor layer grown in the (001) direction of growth and subject to 6-7% of lattice mismatch. This is additionally supported with experimental evidence (optical absorption spectra).Furthermore our model provides a direct way in evaluating the polarization for any crystal structure described on the atomic level. This is mainly beneficial to researchers who use molecular dynamics and empirical methods for predicting bandstructure.The fundamental performance for semiconductor devices can be improved through the use of the small polarization created from strain and is likely to bring advantages in future photovoltaics devices.

No description available.

La recherche de biomarqueurs pour le dépistage, le diagnostique ou le traitement de maladie requiert le développement de dispositifs hautement sensibles alliant un faible coût d’analyse, un faible encombrement et une réponse rapide. Dans ce cadre, nous développons un biocapteur acoustique utilisant des ondes de volume pour permettre la détection d’analyte particulière dans un milieu biologique complexe. La géométrie retenue est une membrane résonante à excitation et détection piézoélectriques intégrées vibrant sur un mode de cisaillement d’épaisseur généré par un champ latéral. Le transducteur utilise les propriétés particulières de l’arséniure de gallium pour assurer une détection sensible et sélective, aussi bien grâce à ses propriétés piézoélectriques que ses possibilités de microfabrication ou de biofonctionnalisation. Dans un premier temps, nous avons dimensionné le dispositif et modélisé son comportement. Une sensibilité à un ajout de masse a pu être estimée à environ 0.1 ng.Hz-1. Nous avons ensuite envisagé la microfabrication du capteur en utilisant uniquement des techniques de microfabrication à faible coût (gravure humide et photolithogravure). Ceci a permis d’obtenir des membranes épaisses (50 μm) de géométrie et d’état de surface maitrisés. Nous avons ensuite envisagé la réalisation de la biointerface grâce au développement d’une interface chimique spécifique permettant d’immobiliser covalemment une monocouche dense de protéine à la surface du GaAs. Cette monocouche a été caractérisée par une analyse originale couplant la microscopie à force atomique (AFM) et la spectrométrie de masse MALDI-TOF. Enfin, les interfaces fluidiques et électriques ont été mises au point et ont permis de tester le dispositif par une mesure d’impédance. / The biomarkers detection for screening, diagnosis or treatment of disease requires the development of highly sensitive devices combining low cost of analysis, a small size and quick responses. In this context, we develop a biosensor using bulk acoustic wave to allow the detection of specific analyte in a complex biological medium. The geometry used is a piezoelectric resonant membrane using shear mode vibration excited by lateral field. The transducer uses the specific properties of gallium arsenide to provide a highly sensitive and selective detection thanks to its piezoelectric properties and also its microfabrication or biofonctionnalisation facilities. First, we dimensioned the device and modeled it behavior. A sensitivity to adding mass has been estimated at 0.1 ng.Hz-1. Then, we considered the sensor microfabrication using only low cost process (photolithography and wet etching). Through these processes, we obtained well formed thick membranes (50μm) with specific surface properties and microstructuration. Next, we realize the biointerface through the development of a specific chemical interface in order to immobilize a dense protein monolayer covalently attached to the GaAs surface. This monolayer was characterized by an original analysis coupling the atomic force microscopy and the mass spectroscopy MALDI-TOF. Finally, fluid and electrical interfaces have been developed and we tested the device by impedance measurements