Orientador: Luis Vicente de Andrade Scalvi / Banca: José Antonio Malmonge / Banca: José Humberto Dias da Silva / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Neste trabalho foi realizada a deposição através da técnica de evaporação resistiva, de filmes finos de GaAs (arseneto de gálio) e de Al (alumínio) com posterior oxidação deste último, formando 'Al IND. 2''O IND. 3' (óxido de alumínio ou alumina) e a caracterização dos filmes de GaAs e da heteroestrutura formada por 'Al IND. 2''O IND. 3' e GaAs. A confecção do dispositivo combinando estes compostos serviu para a investigação das características relevantes do sistema para potencial aplicação em transistores. O trabalho compreendeu investigação sobre as condições de deposição, e foram avaliadas principalmente as características elétricas dos filmes produzidos individualmente. Os resultados apresentados incluem: resistividade em função da temperatura, corrente-voltagem em função da temperatura, difração de raios-X e transmitância na região do infravermelho. Para caracterização do desempenho do sistema 'Al IND. 2''O IND. 3'/GaAs, um transistor simples foi construído sob um substrato de vidro borossilicato com uma camada de GaAs e outra de 'Al IND. 2''O IND. 3'. Os contatos de fonte, dreno e gate foram feitos de In. Essa estrutura permite a medida da corrente de fuga e a avaliação de outras características do sistema. Neste dispositivo foram avaliadas as características corrente-voltagem em função da temperatura, e também a interação com luz, já que GaAs, por apresentar gap direto, torna-se atraente para aplicações opto-eletrônicas. Assim medidas de elétricas foto-induzidas foram realizadas com excitação com fontes de luz branca. Com o intuito de se avaliar a qualidade dos filmes de GaAs obtidos pela evaporação resistiva, tanto a caracterização estrutural quando elétrica também foram feitas em filmes finos de GaAs depositados por sputtering, de modo a se ter um padrão de comparação. / Abstract: In this work, the deposition of GaAs (gallium arsenide) and Al (aluminum) thin films is carried out by the resistive evaporation technique. In the latter case, an oxidation of the film is accomplished, leading to 'Al IND. 2''O IND. 3' (alumina) formation. The characterization of GaAs thin films and the heterostructure formed by 'Al IND. 2''O IND. 3' and GaAs is also carried out. The elaboration of the device combining these compounds allows investigating the relevant characteristics of this system to potential application in transistors. The work evolved investigation on the deposition conditions, and the electrical characteristics of the films were also evaluated separately. Results includes: resistivity as function of temperature, X-ray diffraction and near infrared transmittance. For characterization of the performance of the 'Al IND. 2''O IND. 3'/GaAs system, a simple transistor was built on a borosilicate glass substrate, with a 'Al IND. 2''O IND. 3' layer on top of a GaAs layer. The contacts of source, drain and gate were done using In. This structure allows evaluating the leak current and other characteristics of this system. In this device, it was evaluated the current - voltage characteristics and the interaction with light, because GaAs, due to its direct bandgap, become very attractive for opto-electronic applications. The, the photo-induced electrical measurements were done under excitation with white light. Aiming the evaluation of the quality of films deposited by the resistive evaporation technique, electrical as well as structural characterization were also carried out for GaAs thin films deposited by sputtering, in order to have a comparing parameter. / Mestre

Orientador: Luiz Vicente de Andrade Scalvi / Banca: Valmor Roberto Mastelaro / Banca: Elisabete Aparecida Andrello Rubo / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Neste trabalho é feita a deposição de filmes finos pela técnica de Evaporação Resistiva a partir de pós de Arseneto de Gálio (GaAs) e compostos de GaAs com Óxidos e Cloretos de Érbio (Er) ou Itérbio (Yb). Trata-se de um método relativamente simples de deposição, no qual os compostos são evaporados conjuntamente. O objetivo é observar a eficiência desse método para a produção desses filmes finos, a partir de compostos que possuam diferentes características, tais como consideráveis diferenças de temperaturas de evaporação. Depositamos filmes em diferentes condições e estequiometrias e analisamos as propriedades estruturais pela técnica de difração de raios-X. A composição qualitativa das amostras foi obtida por energia dispersiva de raios-X. As propriedades ópticas foram analisadas através de medidas de transmitância óptica dentro da faixa do visível ao infravermelho médio. Realizamos também a caracterização elétrica através de medidas de resistência em função da temperatura em filmes de GaAs e composto de GaAs com 'ErCl IND 3'. Apresentamos no apêndice uma proposta de investigação das propriedades de transporte elétrico de uma dessas amostras, envolvendo um modelo para cálculo da condutividade. De imediato, a contribuição deste trabalho é para a compreensão dos fenômenos físicos que acontecem durante o processo de crescimento, e a investigação parâmetros de deposição que viabilizem o emprego da técnica para os diferentes materiais evaporados. / Abstract: In this work, thin film deposition is carried out, using the resistive evaporation technique, from powders of gallium arsenide (GaAs) and erbium (Er) or ytterbium (Yb) oxides and chlorides. It is a relatively simple deposition technique, where the compounds are simultaneously evaporated. The goal is to observe the efficiency of this growth method for the production of thin films, from compounds with distinct characteristics, such as high difference between evaporation temperatures. Films have been deposited under different conditions and stoichiometry, and their structural properties were analyzed by X-ray diffraction technique. Sample composition was obtained by X-ray dispersive energy. Optical properties were analyzed through optical transmittance from visible to medium infrared. Electrical characterization was also carried out, using measurements of resistance as function of temperature for GaAs and GaAs with 'ErCl IND 3' compounds. An appendix is also presented, containing a proposal of electrical transport investigation, involving conductivity calculation. The contribution of this work is towards the understanding of physical phenomena that takes place during the growth process, and the investigation of deposition parameters with make reliable the utilization of this technique for the different evaporated materials. / Mestre

Orientador: Jacobus Willibrordus Swart / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T07:19:34Z (GMT). No. of bitstreams: 1 Goes_MarcosAugustode_M.pdf: 31444750 bytes, checksum: e7c5cce48b9c9ec73f1804fee26b6062 (MD5) Previous issue date: 2005 / Resumo: Esta dissertação de mestrado descreve o estudo, projeto e implementação de um receptor optoeletrônico integrado (OEIC) utilizando a tecnologia de transistores bipolares de heterojunção (HBT), fabricados a partir do material semicondutor arseneto de gálio. A grande vantagem deste transistor é o seu alto ganho e baixa resistência de base, o qual possibilita operações na faixa de gigahertz. A integração do estágio de fotodetecção, feita por um fotodiodo do tipo PIN, com o circuito de amplificação em um mesmo circuito integrado é possível, pois o fotodetector é construído com as camadas de base, coletor e subcoletor do transistor HBT. Com isso, as resistências, capacitâncias e indutâncias parasitas presentes na conexão entre estes dois estágios são minimizadas. Isto permite aos receptores monolíticos trabalharem em freqüências mais altas em relação aos receptores híbridos. O circuito fabricado opera com fontes de luz no comprimento de onda de 850 nm e pode ser utilizado em redes locais de curta distância (LAN) / Abstract: This master degree dissertation describes the study, project and implementation of an optoelectronic integrated circuit (OEIC) using the heterojunction bipolar transistors (HBT) technology over a gallium arsenide substrate. The major advantage of this transistor is its high gain and low base resistance, allowing operation at frequencies in the range of gigahertz. The integration of the photodetection stage, performed by a PIN photodetector, with the amplifier circuit in a single chip is possible because the photodetector is built from the base, collector and subcollector layers of the HBT transistor. Thus, the parasitic resistances, capacitances and inductances between the connection of these two stages are minimized. In this way, monolithic receivers can operate at higher frequencies than hybrid receivers. The fabricated circuit is intended to work with 850 nm light sources and can be used in local area networks (LAN) / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

This study focuses on the development of InAs/GaInSb strained-layer superlattice structures by metal organic chemical vapour deposition (MOCVD), and deals with two aspects of the development of InAs/GaInSb SLS’s by MOCVD viz. the deposition of nano-scale (~100 Å) GaInSb layers, and the electrical characterization of unstrained InAs. The first part of this work aims to study the MOCVD growth of GaInSb layers in terms of deposition rate and indium incorporation on the nano-scale. This task is approached by first optimizing the growth of relatively thick (~2 μm) epitaxial films, and then assuming similar growth parameters during nano-scale deposition. The GaInSb layers were grown as part of GaInSb/GaSb quantum well (QW) structures. By using this approach, the GaInSb QW’s (~100 Å) could be characterized with the use of photoluminescence spectroscopy, which, when used in conjunction with transmission electron microscopy and/or X-ray diffractomery, proves useful in the analysis of such small scale deposition. It is shown that the growth rate of GaInSb on the nano-scale approaches the nominal growth rates determined from thick (~2 μm) GaInSb calibration layers. The In incorporation efficiency in nano-layers, however, was markedly lower than what was predicted by the GaInSb calibration layers. This reduction in indium incorporation could be the result of the effects of strain on In incorporation. The choice of substrate orientation for QW deposition was also studied. QW structures were grown simultaneously on both (100) and 2°off (100) GaSb(Te) substrates, and it is shown that growth on non-vicinal substrates is more conducive to the deposition of high quality QW structures. The second part of this study focuses on the electrical characterization of unstrained InAs. It is long known that conventional Hall measurements cannot be used to accurately characterize InAs epitaxial layers, as a result of parallel conduction resulting from surface and/or interface effects. This study looks at extracting the surface and bulk electrical properties of n-type InAs thin films directly from variable magnetic field Hall measurements. For p-type InAs, the situation is complicated by the relatively large electron to hole mobility ratio of InAs which tends to conceal the p-type nature of InAs thin films from Hall measurements. Here, this effect is illustrated by way of theoretical simulation of Hall data.

The importance of infrared (IR) technology (for detection in the 3-5 μm and 8-14 μm atmospheric windows) has spread from military applications to civilian applications since World War II. The commercial IR detector market in these wavelength ranges is dominated by mercury cadmium telluride (MCT) alloys. The use of these alloys has, however, been faced with technological difficulties. One of the materials that have been tipped to be suitable to replace MCT is InAs/InxGa1-xSb strained layer superlattices (SLS’s). Atmospheric pressure metal-organic vapour phase epitaxy (MOVPE) has been used to grow InAs/GaSb strained layer superlattices (SLS’s) at 510 °C in this study. This is a starting point towards the development of MOVPE InAs/InxGa1-xSb SLS’s using the same system. Before the SLS’s could be attempted, the growth parameters for GaSb were optimised. Growth parameters for InAs were taken from reports on previous studies conducted using the same reactor. Initially, trimethylgallium, a source that has been used extensively in the same growth system for the growth of GaSb and InxGa1-xSb was intended to be used for gallium species. The high growth rates yielded by this source were too large for the growth of SLS structures, however. Thus, triethylgallium (rarely used for atmospheric pressure MOVPE) was utilized. GaSb layers (between 1 and 2 μm thick) were grown at two different temperatures (550 °C and 510 °C) with a varying V/III ratio. A V/III ratio of 1.5 was found to be optimal at 550 °C. However, the low incorporation efficiency of indium into GaSb at this temperature was inadequate to obtain InxGa1-xSb with an indium mole fraction (x) of around 0.3, which had previously been reported to be optimal for the performance of InAs/InxGa1-xSb SLS’s, due to the maximum splitting of the valence mini bands for this composition. The growth temperature was thus lowered to 510 °C. This resulted in an increase in the optimum V/III ratio to 1.75 for GaSb and yielded much higher incorporation efficiencies of indium in InxGa1-xSb. However, this lower growth temperature also produced poorer surface morphologies for both the binary and ternary layers, due to the reduced surface diffusion of the adsorbed species. An interface control study during the growth of InAs/GaSb SLS’s was subsequently conducted, by investigating the influence of different gas switching sequences on the interface type and quality. It was noted that the growth of SLS’s without any growth interruptions at the interfaces leads to tensile strained SLS’s (GaAs-like interfaces) with a rather large lattice mismatch. A 5 second flow of TMSb over the InAs surface and a flow of H2 over GaSb surface yielded compressively strained SLS’s. Flowing TMIn for 1 second and following by a flow of TMSb for 4 seconds over the GaSb surface, while flowing H2 for 5 seconds over the InAs surface, resulted in SLS’s with GaAs-like interfacial layers and a reduced lattice mismatch. Temperature gradients across the surface of the susceptor led to SLS’s with different structural quality. High resolution x-ray diffraction (HRXRD) was used to determine the thicknesses as well as the type of interfacial layers. The physical parameters of the SLS’s obtained from simulating the HRXRD spectra were comparable to the parameters obtained from cross sectional transmission electron microscopy (XTEM) images. The thicknesses of the layers and the interface type played a major role in determining the cut-off wavelength of the SLS’s.

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Two-dimensional electron systems in GaAs/AlGaAs heterostructures have provided a platform for investigating numerous phenomena in condensed matter physics. The quantum Hall effect is a particularly remarkable phenomenon due to its topological properties, including chiral edge states with quantized conductance. This report describes progress made in interference measurements of these edge states in electronic Fabry-Perot interferometers. Previous interference experiments in the quantum Hall regime have been stymied by Coulomb charging effects and poor quantum coherence. These Coulomb charging effects have been dramatically suppressed by the implementation of a novel GaAs/AlGaAs heterostructure which utilizes auxiliary screening wells in addition to the primary GaAs quantum well. Using this heterostructure, Aharonov-Bohm interference is measured in very small devices which have greatly improved coherence. Robust Aharonov-Bohm interference is reported at fractional quantum Hall states nu = 1/3 and nu = 2/3. Discrete jumps in phase at nu = 1/3 consistent with anyonic braiding statistics are observed. The report concludes with proposed future experiments, including extending these results to possible non-Abelian quantum Hall states.

abstract: Several key, open questions in astrophysics can be tackled by searching for and mining large datasets for transient phenomena. The evolution of massive stars and compact objects can be studied over cosmic time by identifying supernovae (SNe) and gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling GRBs and their afterglows to probe the jets of GRBs can shed light on the emission mechanism, rate, and energetics of these events. In Chapter 1, I discuss the current state of astronomical transient study, including sources of interest, instrumentation, and data reduction techniques, with a focus on work in the infrared. In Chapter 2, I present original work published in the Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of this work include observing the exoplanet transit of HD189773B, and detecting the nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al. 2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence for a bright-edged jet. In Chapter 4, I present a look back at previous years of RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on the efficiency of following up GRBs detected by the Fermi Space Telescope, before some final remarks and brief discussion of future work in Chapter 5. / Dissertation/Thesis / Doctoral Dissertation Physics 2019

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