abstract: High-performance III-V semiconductors based on ternary alloys and superlattice systems are fabricated, studied, and compared for infrared optoelectronic applications. InAsBi is a ternary alloy near the GaSb lattice constant that is not as thoroughly investigated as other III-V alloys and that is challenging to produce as Bi has a tendency to surface segregate and form droplets during growth rather than incorporate. A growth window is identified within which high-quality droplet-free bulk InAsBi is produced and Bi mole fractions up to 6.4% are obtained. Photoluminescence with high internal quantum efficiency is observed from InAs/InAsBi quantum wells. The high structural and optical quality of the InAsBi materials examined demonstrates that bulk, quantum well, and superlattice structures utilizing InAsBi are an important design option for efficient infrared coverage. Another important infrared material system is InAsSb and the strain-balanced InAs/InAsSb superlattice on GaSb. Detailed examination of X-ray diffraction, photoluminescence, and spectroscopic ellipsometry data provides the temperature and composition dependent bandgap of bulk InAsSb. The unintentional incorporation of approximately 1% Sb into the InAs layers of the superlattice is measured and found to significantly impact the analysis of the InAs/InAsSb band alignment. In the analysis of the absorption spectra, the ground state absorption coefficient and transition strength of the superlattice are proportional to the square of the electron-hole wavefunction overlap; wavefunction overlap is therefore a major design parameter in terms of optimizing absorption in these materials. Furthermore in addition to improvements through design optimization, the optical quality of the materials studied is found to be positively enhanced with the use of Bi as a surfactant during molecular beam epitaxy growth. A software tool is developed that calculates and optimizes the miniband structure of semiconductor superlattices, including bismide-based designs. The software has the capability to limit results to designs that can be produced with high structural and optical quality, and optimized designs in terms of maximizing absorption are identified for several infrared superlattice systems at the GaSb lattice constant. The accuracy of the software predictions are tested with the design and growth of an optimized mid-wave infrared InAs/InAsSb superlattice which exhibits superior optical and absorption properties. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

abstract: InAsBi is a narrow direct gap III-V semiconductor that has recently attracted considerable attention because its bandgap is tunable over a wide range of mid- and long-wave infrared wavelengths for optoelectronic applications. Furthermore, InAsBi can be integrated with other III-V materials and is potentially an alternative to commercial II-VI photodetector materials such as HgCdTe. Several 1 μm thick, nearly lattice-matched InAsBi layers grown on GaSb are examined using Rutherford backscattering spectrometry and X-ray diffraction. Random Rutherford backscattering measurements indicate that the average Bi mole fraction ranges from 0.0503 to 0.0645 for the sample set, and ion channeling measurements indicate that the Bi atoms are substitutional. The X-ray diffraction measurements show a diffraction sideband near the main (004) diffraction peak, indicating that the Bi mole fraction is not laterally uniform in the layer. The average out of plane tetragonal distortion is determined by modeling the main and sideband diffraction peaks, from which the average unstrained lattice constant of each sample is determined. By comparing the Bi mole fraction measured by random Rutherford backscattering with the InAsBi lattice constant for the sample set, the lattice constant of zinc blende InBi is determined to be 6.6107 Å. Several InAsBi quantum wells tensilely strained to the GaSb lattice constant with dilute quantities of Bi are characterized using photoluminescence spectroscopy. Investigation of the integrated intensity as a function of carrier excitation density spanning 5×1025 to 5×1026 cm-3 s-1 indicates radiative dominated recombination and high quantum efficiency over the 12 to 250 K temperature range. The bandgap of InAsBi is ascertained from the photoluminescence spectra and parameterized as a function of temperature using the Einstein single oscillator model. The dilute Bi mole fraction of the InAsBi quantum wells is determined by comparing the measured bandgap energy to that predicted by the valence band anticrossing model. The Bi mole fraction determined by photoluminescence agrees reasonably well with that estimated using secondary ion mass spectrometry. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2016

abstract: In this work, transport in nanowire materials and nanowire field effect transistors is studied using a full band Monte Carlo simulator within the tight binding basis. Chapter 1 is dedicated to the importance of nanowires and nanoscale devices in present day electronics and the necessity to use a computationally efficient tool to simulate transport in these devices. Chapter 2 discusses the calculation of the full band structure of nanowires based on an atomistic tight binding approach, particularly noting the use of the exact same tight binding parameters for bulk band structures as well as the nanowire band structures. Chapter 3 contains the scattering rate formula for deformation potential, polar optical phonon, ionized impurity and impact ionization scattering in nanowires using Fermi’s golden rule and the tight binding basis to describe the wave functions. A method to calculate the dielectric screening in 1D systems within the tight binding basis is also described. Importantly, the scattering rates of nanowires tends to the bulk scattering rates at high energies, enabling the use of the same parameter set that were fitted to bulk experimental data to be used in the simulation of nanowire transport. A robust and efficient method to model interband tunneling is discussed in chapter 4 and its importance in nanowire transport is highlighted. In chapter 5, energy relaxation of excited electrons is studied for free standing nanowires and cladded nanowires. Finally, in chapter 6, a full band Monte Carlo particle based solver is created which treats confinement in a full quantum way and the current voltage characteristics as well as the subthreshold swing and percentage of ballistic transport is analyzed for an In0.7Ga0.3As junctionless nanowire field effect transistor. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

abstract: Conductance fluctuations associated with quantum transport through quantumdot systems are currently understood to depend on the nature of the corresponding classical dynamics, i.e., integrable or chaotic. There are a couple of interesting phenomena about conductance fluctuation and quantum tunneling related to geometrical shapes of graphene systems. Firstly, in graphene quantum-dot systems, when a magnetic field is present, as the Fermi energy or the magnetic flux is varied, both regular oscillations and random fluctuations in the conductance can occur, with alternating transitions between the two. Secondly, a scheme based on geometrical rotation of rectangular devices to effectively modulate the conductance fluctuations is presented. Thirdly, when graphene is placed on a substrate of heavy metal, Rashba spin-orbit interaction of substantial strength can occur. In an open system such as a quantum dot, the interaction can induce spin polarization. Finally, a problem using graphene systems with electron-electron interactions described by the Hubbard Hamiltonian in the setting of resonant tunneling is investigated. Another interesting problem in quantum transport is the effect of disorder or random impurities since it is inevitable in real experiments. At first, for a twodimensional Dirac ring, as the disorder density is systematically increased, the persistent current decreases slowly initially and then plateaus at a finite nonzero value, indicating remarkable robustness of the persistent currents, which cannot be discovered in normal metal and semiconductor rings. In addition, in a Floquet system with a ribbon structure, the conductance can be remarkably enhanced by onsite disorder. Recent years have witnessed significant interest in nanoscale physical systems, such as semiconductor supperlattices and optomechanical systems, which can exhibit distinct collective dynamical behaviors. Firstly, a system of two optically coupled optomechanical cavities is considered and the phenomenon of synchronization transition associated with quantum entanglement transition is discovered. Another useful issue is nonlinear dynamics in semiconductor superlattices caused by its key potential application lies in generating radiation sources, amplifiers and detectors in the spectral range of terahertz. In such a system, transition to multistability, i.e., the emergence of multistability with chaos as a system parameter passes through a critical point, is found and argued to be abrupt. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

abstract: Amorphous materials can be uniformly deposited over a large area at lower cost compared to crystalline semiconductors (Silicon or Germanium). This property along with its high resistivity and wide band-gap found many applications in devices like rectifiers, xerography, xero-radiography, ultrahigh sensitivity optical cameras, digital radiography, and mammography (2D and 3D tomosynthesis). Amorphous selenium is the only amorphous material that undergoes impact ionization where only holes avalanche at high electric fields. This leads to a small excess noise factor which is a very important performance comparison matrix for avalanche photodetectors. Thus, there is a need to model high field avalanche process in amorphous selenium. At high fields, the transport in amorphous selenium changes from low values of activated trap-limited drift mobility to higher values of band transport mobility, via extended states. When the transport shifts from activated mobility with a high degree of localization to extended state band transport, the wavefunction of the amorphous material resembles that of its crystalline counterpart. To that effect, crystalline monoclinic selenium which has the closest resemblance to vapor deposited amorphous selenium has been studied. Modelling a crystalline semiconductor makes calculations simpler. The transport phenomena in crystalline monoclinic selenium is studied by using a bulk Monte Carlo technique to solve the semi-classical Boltzman Transport equation and thus calculate vital electrical parameters like mobility, critical field and mobility variations against temperatures. The band structure and the density of states function for monoclinic selenium was obtained by using an atomistic simulation tool, the Atomistic Toolkit in the Virtual Nano Lab, Quantum Wise, Copenhagen, Denmark. Moreover, the velocity and energy against time characteristics have been simulated for a wide range of electric fields (1-1000 $\frac{kV}{cm}$), which is further used to find the hole drift mobility. The low field mobility is obtained from the slope of the velocity vs. electric field plot. The low field hole mobility was calculated to be 5.51 $\frac{cm^{2}}{Vs}$ at room temperature. The experimental value for low field hole mobility is 7.29 $\frac{cm^{2}}{Vs}$. The energy versus electric field simulation at high fields is used to match the experimental onset of avalanche (754 $\frac{kV}{cm}$) for an ionization threshold energy of 2.1 eV. The Arrhenius plot for mobility against temperature is simulated and compared with published experimental data. The experimental and simulation results show a close match, thus validating the study. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

Inserir conteúdos de Física Quântica no Ensino Médio torna-se um desafio para os professores, tanto por uma possível falta de preparo como pela falta de incentivo. Apesar da existência de materiais didáticos disponíveis, raramente os professores sentem-se preparados para abordar tais conteúdos em sala de aula. Além disso, o atual currículo do Ensino Médio bem como o programa ENEM, não estimulam ao ensino do assunto aqui referido. No entanto, em função da importância da abordagem da Física Quântica, e também frente à propagação de versões místicas e de representações sociais, é preciso continuar tentando contribuir para que essa inserção venha a ocorrer futuramente. Nesse sentido, foi elaborada uma unidade de ensino sobre tópicos de Física Quântica com a intenção de estimular o interesse e a curiosidade do aluno. Como referencial teórico foi utilizada a teoria de aprendizagem de David Ausubel, buscando desenvolver uma aprendizagem significativa dos conteúdos selecionados da Física Quântica a partir de conhecimentos prévios existentes na estrutura cognitiva dos alunos. A proposta foi elaborada seguindo os passos das Unidades de Ensino Potencialmente Significativas – UEPS (MOREIRA, 2011) onde, num primeiro momento foi feito o levantamento dos conhecimentos prévios dos alunos, em seguida foi apresentado o conteúdo de uma forma mais geral e, a partir daí, cada assunto foi abordado de forma mais específica, visando à diferenciação progressiva e à reconciliação integradora. Os conceitos abordados foram quantização, incerteza, estado e superposição de estados, apresentados de acordo com os passos da UEPS. A implementação do trabalho foi realizada em quatro turmas de 3ª série do Ensino Médio da E. E. E. M. Carlos Antonio Kluwe, em Bagé, RS, durante os meses de outubro, novembro e dezembro de 2011. As quatro turmas, denominadas A, B, C e D, foram divididas em dois grupos. O primeiro grupo, formado pelas turmas A e B iniciou as atividades em 10 de outubro de 2011 e o segundo grupo, formado pelas turmas C e D iniciou as atividades em 31 de outubro. Dentre as atividades desenvolvidas são analisados de forma qualitativa os mapas mentais e mapas conceituais elaborados em duplas, bem como a comparação entre eles, e são mostrados os trabalhos livres confeccionados pelos alunos e o jornal de cada turma Ainda são apresentados alguns comentários de estudantes sobre seu desenvolvimento na compreensão dos conceitos abordados na proposta. A análise feita a partir dos resultados obtidos forneceu indícios de aprendizagem significativa, que é o objetivo de uma UEPS. São apresentados também alguns comentários que indicam a boa receptividade da proposta, que encoraja novas aplicações. / It has become a challenge to high school teachers to include contents of quantum physics in the school curriculum not only for the lack of due preparation but for the scarcity of incentive. In spite of available educational resources, teachers seldom feel ready to approach such contents in the classroom. Furthermore, the present high school curriculum as well as the National High School Exam (ENEM) do not seem to encourage the teaching of quantum physics. Nevertheless, because of the relevance of quantum physics and the dissemination of its mystical versions with their social representations, it is necessary to continue attempting at contributing to make this insertion possible in the near future. In this sense, a teaching unit on topics of quantum physics was developed with the purpose of motivating the students ’ interest and curiosity. David Ausubel’s theory of meaningful learning was used a its theoretical framework, so as to facilitate the occurrence of meaningful learning of the chosen contents of quantum physics based on the students’ prior knowledge about the subject. The proposal was developed in agreement with the steps of the Potentially Meaningful Teaching Units – PMTU (Moreira, 2011), according to which the first step was to make a survey of the students’ prior knowledge followed by a general presentation of the contents. From there on, each topic received a more specific/extensive treatment aiming at progressive differentiation and integrative reconciliation. The concepts involved in this study were quantization, uncertainty, state, and superposition of states and they were presented according to the PMTU’s steps. Implementation of this proposal occurred in four different classes of the 3rd year of high school at the State School E.M. Carlos Antonio Kluwe, Bagé, RS, Brazil, from October to December of 2011. These four classes, named A, B, C, and D, were divided into two groups. The first one, formed by classes A and B, started their activities on the October 10, 2011, while the second group, classes C and D, started them on October 31, 2011. The activities performed by the students, such as mind maps and concept maps drawn in pairs, as well as their comparison were qualitatively analysed. There are also shown free-choice works the students produced, as well as the newspaper that each of the classes put together. In addition, some of the students’ comments on their own development regarding the concepts approached in this proposal are presented. The analysis based on obtained results suggested evidence of the occurrence of meaningful learning, which is the aim of a PMTU. Furthermore, some comments that might indicate a fair receptivity to the proposal are also set forth since they seem to encourage new implementations of this proposal.

A simulação de cores corresponde à essência do processo de síntese de imagens realistas. Em se tratando de minerais, a presença de uma dada impureza, ou uma variação de sua concentração, pode fazer com que alguns materiais sofram alterações dramáticas em suas cores. Por exemplo, enquanto o quartzo puro é transparente, a ametista é um tipo violeta de quartzo, cuja cor é determinada pela presença de traços de ferro. A quantidade de ferro define o matiz percebido. A cor apresentada por um mineral pode ser determinada com base no seu espectro de absorção. No entanto, a definição de todas as variações possíveis é impraticável e, portanto, tal informação está disponível apenas para um subconjunto dos minerais existentes. Esta dissertação apresenta uma proposta para estimar a cor de ágatas, bem como para simular as cores de ágatas sintéticas (inexistentes). A abordagem utilizada baseia-se nos fundamentos da teoria quântica, e parte de uma descrição da molécula de sílica que se deseja simular. À esta, pode-se adicionar quantidades diferentes de impurezas e alterar o número de átomos incluídos na simulação. O resultado obtido é o espectro de absorção do mineral, que pode então ser utilizado para determinar a cor da ágata com a composição desejada. Embora uma simulação detalhada de todo o processo seja uma tarefa computacionalmente extremamente cara, esta dissertação apresenta alguns resultados que corroboram com a correção da solução proposta. Também é apresentada uma técnica independente que pode ser utilizada para definir um volume de ágata com base em uma imagem 2D. / Color simulation is the essence of realistic image synthesis. In the case of minerals, the presence of a given impurity, or a variation of its concentration, can cause some materials to experience dramatic changes in color. For instance, while pure quartz is transparent, amethyst is a violet type of quartz, whose color is determined by the presence of traces of iron. The amount of iron defines the perceived hue. The color presented by a mineral can be determined based on its absorption spectrum. However, defining all possible variations is impractical and, therefore, such information is available only for a subset of the existing minerals. This thesis presents an approach for simulating the colors of existent agates, as well as for predicting the colors for (non-existent) synthetic ones. The approach is based on the fundamentals of quantum theory, and starts with the description of the silica molecule one wants to simulate. One can add different amounts of impurities, and alter the number of atoms included in the simulation. The obtained result is the absorption spectra of the mineral, which can then be used for determining the color of the agate with the desired composition. Although a detailed simulation of the entire process is extremely computationally-expensive, the thesis presents some results that corroborate the correctness of the proposed solution. It also introduces a standalone technique for defining agate volumes based on 2D images of agates.

Apresentamos, nesta tese, uma investigação sobre a estabilização ontológica do fóton, um actante inicialmente articulado no contexto da primeira revolução da Física Quântica. Partindo dos Estudos da Ciência de Bruno Latour, entendemos a ciência como uma rede que se estende por diferentes setores da sociedade e que, portanto, lida com diferentes gêneros do discurso. Além de identificar a importância do gênero científico (artigos seminais) no processo de autonomização dos fatos científicos, também reconhecemos que, na comunidade da Física, os livros didáticos, ou manuais de instrução, tem papel crucial no estabelecimento dos problemas exemplares bem como das teorias hegemônicas, tanto que, hoje, é possível um físico se formar sem estudar os artigos originais sobre Física Quântica. Ademais, os livros didáticos de ciências da Educação Básica são, atualmente, responsáveis pela extensão da rede científica para além dos laboratórios, autonomizando actantes como o fóton em esferas mais amplas da sociedade, papel que Latour poderia chamar de representação pública. O objetivo desta pesquisa é investigar a interação entres esses três gêneros do discurso (artigos seminais, livros didáticos de ensino superior e livros didáticos de ensino médio) e interpretar como que a estabilização ontológica do fóton é mediada por cada um deles. Ao fazer isso, estamos estendendo o programa de pesquisa de Latour em, pelo menos, três sentidos. Primeiramente, incluímos o papel do contexto didático na rede da ciência. Segundo, nossos objetos de investigação estão separados por um intervalo temporal maior do que o usual (aproximadamente cem anos). E, por fim, enquanto Latour dedica-se, principalmente, ao estudo de ciências empíricas, nosso trabalho volta-se para assim chamada Física Teórica, levantando questões ontológicas não discutidas originalmente por Latour. Para dar conta dessa extensão, o presente trabalho está dividido em duas partes. A parte I (Referencial Teórico) traz três artigos sobre as ideias de Bruno Latour e as possibilidades de sua aplicação na pesquisa em Educação em Ciências, o que temos chamado de Sociologia Simétrica da Educação em Ciências ou Estudos da Educação em Ciência. A parte II (Estudos Empíricos) traz quatro artigos (dois sobre as relações entre artigos seminais e livros de ensino superior e dois sobre as relações entre artigos seminais, livros de ensino superior e livros de ensino médio). O primeiro estudo empírico traz uma análise metalinguística do artigo original de Einstein de 1905 em que o quantum é articulado pela primeira vez sem que se precisasse recorrer a nenhum laboratório. No segundo artigo, apresentamos uma análise conceitual e matemática dos artigos de de Broglie e usamos as ideias de Latour para discutir o papel dos livros didáticos na autonomização de sua teoria. No terceiro artigo, analisamos visões epistemológicas em livros didáticos de Física aprovados no Plano Nacional do Livro Didático do Ensino Médio de 2015. E, no quarto artigo, discutimos a narrativa sobre o fóton nesses livros a partir de uma articulação teórica entre ideias de Latour e Bakhtin. Nossos principais resultados apontam o papel articulador da matemática na estabilização de actantes físicos e o papel ativo dos autores de livros didáticos na estabilização do fóton a partir da hibridização de diferentes visões e do uso de mecanismos de causação reversa. / We present an investigation about the ontological stabilization of photon, an actant articulated initially in the context of the first Quantum Revolution. Departing from Bruno Latour’s Science Studies, we take Science as a network spread through different sectors of society and which deals with different speech genders. Besides of identifying the importance of the scientific gender (scientific papers) in the process of autonomation of scientific facts, we also recognize that, in the Physics community, textbooks play a crucial role in the establishment of traditional problems as well as hegemonic theories. Nowadays, someone can conclude an undergraduate course on Physics without having read any of the original papers about Quantum Physics. Furthermore, textbooks in Basic Education are responsible by the extension of the scientific network beyond laboratories, autotomizing actants like the photon in wider spheres of society, what Latour would call public representation. The goal of this research is to investigate the interaction among these three speech genders (original papers, undergraduate textbooks and high school textbooks) and to interpret how the ontological stabilization of photon is mediated by each of them. By doing so, we are extending Latour’s research program in at least three ways. First, we include the didactic context in the science network. Second, our objects of investigation are separated in time by a greater gap (about a hundred years). And third, while Latour studied chiefly the empirical sciences, our work is directed towards the Theoretical Physics, raising ontological questions that were not discussed by Latour. To allow this extension, the work is divided in two parts. Part I (Theoretical Framework) presents three papers about Bruno Latour’s ideas and the possibilities of their application in the research on Science Education, what we have called The Symmetric Sociology of Science Education. Part II (Empirical Studies) presents four papers (two about the relation between original papers and undergraduate textbooks and two about the relation between original papers and high school textbooks). The first empirical study presents a metalinguistic analysis of 1905 Einstein’s paper in which the quantum is articulated by the first time without requiring any laboratory trial. In the second paper, we present a conceptual and mathematical analysis of de Broglie’s papers and we use Latour’s ideas to discuss the role of textbooks in the atomization of his theory. In the third paper, we analyze the epistemological visions present in the Physics textbooks approved by the 2015 National Plan of Textbook. In the fourth paper, we discuss the narrative about the photon present in these books departing from a theoretical articulation between Latour’s and Bakhtin’s ideas. Our chief results point to the articulating role of mathematics in the stabilization of physical actants and the active role of textbooks authors in the stabilization of photon through the hybridization of different visions and the use of the mechanisms of reverse causation.

abstract: Solution methods for certain linear and nonlinear evolution equations are presented in this dissertation. Emphasis is placed mainly on the analytical treatment of nonautonomous differential equations, which are challenging to solve despite the existent numerical and symbolic computational software programs available. Ideas from the transformation theory are adopted allowing one to solve the problems under consideration from a non-traditional perspective. First, the Cauchy initial value problem is considered for a class of nonautonomous and inhomogeneous linear diffusion-type equation on the entire real line. Explicit transformations are used to reduce the equations under study to their corresponding standard forms emphasizing on natural relations with certain Riccati(and/or Ermakov)-type systems. These relations give solvability results for the Cauchy problem of the parabolic equation considered. The superposition principle allows to solve formally this problem from an unconventional point of view. An eigenfunction expansion approach is also considered for this general evolution equation. Examples considered to corroborate the efficacy of the proposed solution methods include the Fokker-Planck equation, the Black-Scholes model and the one-factor Gaussian Hull-White model. The results obtained in the first part are used to solve the Cauchy initial value problem for certain inhomogeneous Burgers-type equation. The connection between linear (the Diffusion-type) and nonlinear (Burgers-type) parabolic equations is stress in order to establish a strong commutative relation. Traveling wave solutions of a nonautonomous Burgers equation are also investigated. Finally, it is constructed explicitly the minimum-uncertainty squeezed states for quantum harmonic oscillators. They are derived by the action of corresponding maximal kinematical invariance group on the standard ground state solution. It is shown that the product of the variances attains the required minimum value only at the instances that one variance is a minimum and the other is a maximum, when the squeezing of one of the variances occurs. Such explicit construction is possible due to the relation between the diffusion-type equation studied in the first part and the time-dependent Schrodinger equation. A modication of the radiation field operators for squeezed photons in a perfect cavity is also suggested with the help of a nonstandard solution of Heisenberg's equation of motion. / Dissertation/Thesis / Ph.D. Applied Mathematics for the Life and Social Sciences 2013

abstract: Photodetectors in the 1.7 to 4.0 μm range are being commercially developed on InP substrates to meet the needs of longer wavelength applications such as thermal and medical sensing. Currently, these devices utilize high indium content metamorphic Ga1-xInxAs (x > 0.53) layers to extend the wavelength range beyond the 1.7 μm achievable using lattice matched GaInAs. The large lattice mismatch required to reach the extended wavelengths results in photodetector materials that contain a large number of misfit dislocations. The low quality of these materials results in a large nonradiative Shockley Read Hall generation/recombination rate that is manifested as an undesirable large thermal noise level in these photodetectors. This work focuses on utilizing the different band structure engineering methods to design more efficient devices on InP substrates. One prospective way to improve photodetector performance at the extended wavelengths is to utilize lattice matched GaInAs/GaAsSb structures that have a type-II band alignment, where the ground state transition energy of the superlattice is smaller than the bandgap of either constituent material. Over the extended wavelength range of 2 to 3 μm this superlattice structure has an optimal period thickness of 3.4 to 5.2 nm and a wavefunction overlap of 0.8 to 0.4, respectively. In using a type-II superlattice to extend the cutoff wavelength there is a tradeoff between the wavelength reached and the electron-hole wavefunction overlap realized, and hence absorption coefficient achieved. This tradeoff and the subsequent reduction in performance can be overcome by two methods: adding bismuth to this type-II material system; applying strain on both layers in the system to attain strain-balanced condition. These allow the valance band alignment and hence the wavefunction overlap to be tuned independently of the wavelength cutoff. Adding 3% bismuth to the GaInAs constituent material, the resulting lattice matched Ga0.516In0.484As0.970Bi0.030/GaAs0.511Sb0.489superlattice realizes a 50% larger absorption coefficient. While as, similar results can be achieved with strain-balanced condition with strain limited to 1.9% on either layer. The optimal design rules derived from the different possibilities make it feasible to extract superlattice period thickness with the best absorption coefficient for any cutoff wavelength in the range.   / Dissertation/Thesis / M.S. Electrical Engineering 2013