Neste trabalho, estudamos o crescimento epitaxial por feixe molecular assim como as propriedades ópticas e estruturais de camadas de InGaAs depositadas sobre substratos de GaAs(001) com diferentes ângulos e direções de corte. Um ênfase foi dada à investigação da segregação dos átomos de Índio que modifica consideravelmente o perfil de potencial das heteroestruturas e influencia as características dos dispositivos contendo este tipo de camadas. Um novo método experimental baseado em medidas de difração de elétrons de alta energia (RHEED) possibilitou a determinação in situ e em tempo real do coeficiente de segregação dos átomos de Índio e, conseqüentemente, do perfil de composição das camadas de InGaAs. Medidas de raios X e de fotoluminescência em baixa temperatura foram realizadas em amostras de poços quânticos de InGaAs e confirmaram, a posteriori, os resultados obtidos pela técnica RHEED. Foi também demonstrado que o uso de substratos desorientados podia reduzir levemente o efeito de segregação e melhorar as propriedades ópticas das camadas em baixa temperatura. / In this work, we investigated the molecular-beam-epitaxy growth as well as the optical and structural properties of InGaAs layers deposited on top of GaAs (001) substrates with different miscut angles and directions. We emphasized the investigation of the segregation of In atoms that considerably modifies the potential profile of the heterostructures and influences the characteristics of the devices based on this type of layers. A new experimental method involving the diffraction of high-energy electrons (RHEED) allowed the in-situ and real-time determination of the segregation coefficient of the In atoms and, consequently, of the compositional profile of the InGaAs layers. X-rays and low-temperature photoluminescence measurements were carried out InGaAs quantum wells and confirmed, a posterior, the results obtained by the RHEED method. It was also demonstrated that the use of vicinal substrates slight reduces the segregation effect and improves the optical properties of the layers at low temperature.

Este trabalho teve por objetivo o desenvolvimento de uma metodologia de análise estrutural de heteroestruturas, ou seja, estruturas formadas pela combinação de materiais diferentes depositados em camadas alternadas. O trabalho focalizou aspectos não apenas referentes às técnicas de difração de raios X, comumente utilizadas na caracterização estrutural destes novos materiais, mas também se concentrou no desenvolvimento de cálculos teóricos da intensidade difratada pelos raios X, os quais, comparados com os dados experimentais, dão informação precisa acerca do que poderíamos denominar qualidade estrutural. Uma comparação entre resultados obtidos com a teoria Cinemática Dinâmica foram também explorados e o alcance das duas teorias foi discutido. Este procedimento, embora tenha sido aplicado para a análise de heteroestruturas a base de semicondutores cristalinos, pode também ser aplicado, por exemplo, ao estudo de heteroestruturas magnéticas. É sempre fundamental no processo de desenvolvimento de novos materiais caracterizar as amostras após o crescimento, a fim de comparar os resultados experimentais com os valores nominais obtidos do procedimento de deposição. Em particular, neste trabalho, a caracterização estrutural de super-redes deformadas de Si 1-xGex/Ge e Si/Ge, crescidas sobre substratos de Ge e Si, respectivamente, realizou-se através do uso de técnicas não destrutivas de difração de raios X, envolvendo a medição dos parâmetros próprios das super-redes como: período, número de camadas atômicas, parâmetros de rede e deformação. / The aim of this work was the development of a methodology for the structural analysis of heterostructures, i. e., structures formed by the combination of different materials, deposited as alternate layers. The work focused on aspects not only related to x-ray diffraction techniques, usually utilized for the structural characterization of these new materials, but also it concentrated on the development of theorical calculations of the x-ray diffracted intensity, which were compared with experimental data in order to determine the so-called structural quality. The results obtained with the Kinematical and Dinamical X-ray Diffraction theories were explored and the scope of both theories was discussed. Even though this procedure was applied to the analysis of heterostrutures based on crystalline semiconductors, it also can be used, for example, to the study of magnetic multilayers. It is always fundamental in the development process of new materials to characterize the samples after growth, in order to compare the experimental results with the nominal values obtained by the deposition procedure. ln particular, in this work, the structural characterization of Si1-xGex /Ge and Si/Ge strained superlattices, deposited on Ge and Si substrate, respectively, was performed by means of non-destructive x-ray diffraction techniques, measuring superlattices parameters as: periodicity, number of atomic layers, lattice parameters and strain.

Wan Shan Mei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract / Acknowledgements / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- History of Semiconductor Optical Amplifier In Optical Networks --- p.1 / Chapter 1.2 --- Comparisons of SOAs With Other Amplifiers --- p.3 / Chapter 1.2.1 --- Erbium Doped Fiber Amplifier (EDFA) --- p.3 / Chapter 1.2.2 --- Raman Amplifiers --- p.5 / Chapter 1.2.3 --- Parametric Amplifiers --- p.7 / Chapter 1.3 --- The Need of SO A for Wavelength Conversion in Optical Networks --- p.8 / Chapter 1.3.1 --- General Applications of SOAs --- p.8 / Chapter 1.3.2 --- Wavelength Conversion of SOAs --- p.9 / Chapter 1.4 --- Cross Gain Modulation (XGM) --- p.11 / Chapter 1.5 --- Cross Phase Modulation (XPM) --- p.13 / Chapter 1.6 --- Four Wave Mixing (FWM) --- p.16 / Chapter 1.7 --- Bi-refringence Switching --- p.19 / Chapter 1.8 --- Conclusion --- p.22 / Chapter 1.9 --- References --- p.22 / Chapter Chapter 2 --- Physics of Semiconductor Optical Amplifier and Background of Quantum Well Semiconductor Optical Amplifier / Chapter 2.1 --- Physics of Semiconductor Optical Amplifier --- p.26 / Chapter 2.1.1 --- General Structure of SOAs --- p.26 / Chapter 2.1.2 --- Principles of Optical Amplification --- p.27 / Chapter 2.1.3 --- Material Gain Coefficient --- p.29 / Chapter 2.1.4 --- Bulk Material Properties of SOAs --- p.32 / Chapter 2.1.5 --- Spontaneous Emission Noise --- p.34 / Chapter 2.1.6 --- Polarization Sensitivity --- p.37 / Chapter 2.1.7 --- Dynamics Effects --- p.38 / Chapter 2.2 --- Background of Quantum Wells Semiconductor Optical Amplifier --- p.38 / Chapter 2.2.1 --- Definition of Quantum Well SOAs --- p.38 / Chapter 2.2.2 --- Different Types of Quantum Well SOAs --- p.39 / Chapter 2.2.3 --- Quantization of the Conduction Band and Valence Band --- p.40 / Chapter 2.3 --- Comparison Between Bulk and Quantum Well SOAs --- p.44 / Chapter 2.3.1 --- Gain Bandwidth --- p.44 / Chapter 2.3.2 --- Polarization Dependence --- p.44 / Chapter 2.3.3 --- Saturation Output Power --- p.45 / Chapter 2.4 --- Conclusion --- p.46 / Chapter 2.5 --- References --- p.46 / Chapter Chapter 3 --- Wideband Wavelength Conversion by XGM in Asymmetrical Multiple Quantum Well Semiconductor Optical Amplifier (AMQW-SOA) / Chapter 3.1 --- Background of Wideband Asymmetrical Multiple Quantum Well Semiconductor Optical Amplifier --- p.47 / Chapter 3.1.1 --- Sequence Influence of Non-identical InGaAsP Quantum Wells on SO A Broadband Characteristics --- p.47 / Chapter 3.1.2 --- Influence of Separate Confinement Heterostructure on Emission Bandwidth InGaAsP SOAs --- p.54 / Chapter 3.2 --- Wideband Wavelength Conversion --- p.58 / Chapter 3.2.1 --- First Experiment of Wideband Wavelength Conversion from 1.5 μm to 14 μm by XGM in AMQW-SOA --- p.62 / Chapter 3.2.2 --- Second Experiment of Wideband Wavelength Conversion from 1.5 μm to 1.4μm by XGM with 2.5 Gbit/s in AMQW-SOA --- p.64 / Chapter 3.2.3 --- Third Experiment of Investigation of Wavelength Conversion from 15 μm to 1.5 μm/1.3 μm by XGM in AMQW-SOA --- p.67 / Chapter 3.3 --- Conclusion --- p.69 / Chapter 3.4 --- References --- p.71 / Chapter Chapter 4 --- Wavelength Conversion by Birefringence Switchingin Asymmetrical Multiple Quantum Well Semiconductor Optical Amplifier (AMQW-SOA) / Chapter 4.1 --- First Experiment of Wideband Wavelength Conversion from 1.5 μm to 1.4 μm by Birefringence Switching in AMQW-SOA --- p.74 / Chapter 4.2 --- Second Experiment of Investigation of Wavelength Conversion from 1.5 μm to 1.5μm by Birefringence Switching in AMQW-SOA --- p.76 / Chapter 4.3 --- Conclusion --- p.78 / Chapter 4.4 --- References --- p.79 / Chapter Chapter 5 --- Asymmetrical Multiple Quantum Well Semiconductor Optical Amplifier (AMQW-SOA) for Pattern-Effect Free Gain / Chapter 5.1 --- Examples Methods of Pattern Effect Compensation --- p.81 / Chapter 5.1.1 --- Suppression of Pattern Dependent Effects from a Semiconductor Optical Amplifier using an Optical Delay Interferometer (ODI) / Chapter 5.1.2 --- Acceleration of Gain Recovery in QD-SOA --- p.84 / Chapter 5.2 --- Background Theory of Quantum Well Reservoirs and Carrier Transit Time --- p.87 / Chapter 5.3 --- First Experiment of Pattern Effect Free Amplification in AMQW-SOA --- p.92 / Chapter 5.4 --- Second Experiment of Pattern Effect Free Amplification in AMQW-SOA --- p.97 / Chapter 5.5 --- Conclusion --- p.102 / Chapter 5.6 --- References --- p.103 / Chapter Chapter 6 --- Conclusion and Future Work / Chapter 6.1 --- Conclusion --- p.105 / Chapter 6.2 --- Future Work --- p.108 / Appendix Butterfly Photonic Packaging --- p.109

Iu Kwan Sai = 以光致發光譜和高解析度X射線衍射譜研究砷銻化鎵外延層和量子井 / 姚昀樨. / On t.p. "̳x" is subscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 93-95). / Text in English; abstracts in English and Chinese. / Iu Kwan Sai = Yi guang zhi fa guang pu he gao jie xi du X she xian yan she pu yan jiu shen ti hua jia wai yan ceng he liang zi jing / Yao Yunxi. / ACKNOWLEDGMENTS --- p.i / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.v / LIST OF TABLES --- p.vii / LIST OF FIGURES --- p.viii / Chapter 1. --- INTRODUTION --- p.1 / Chapter 1.1 --- Motivations --- p.1 / Chapter 1.2 --- Historical Works --- p.1 / Chapter 1.3 --- This Study --- p.3 / Chapter 1.4 --- Growth Conditions of GaAs1-xSbx Alloy --- p.4 / Chapter 2. --- EXPERIMENTAL PROCEDURES --- p.5 / Chapter 2.1 --- High Resolution X-Ray Diffraction (HRXRD) --- p.5 / Chapter 2.1.1 --- The Use of HRXRD --- p.5 / Chapter 2.1.2 --- Setup of the High Resolution X-Ray Diffractometer --- p.7 / Chapter 2.1.3 --- Types of Measurements --- p.8 / Chapter 2.2 --- Photoluminescence (PL) Spectrometer --- p.10 / Chapter 2.2.1 --- The Use of PL --- p.10 / Chapter 2.2.2 --- Setup of PL spectrometer --- p.10 / Chapter 2.2.3 --- types of Measurements --- p.13 / Chapter 3. --- CHARACTERIZATION --- p.14 / Chapter 3.1 --- High Resolution X-Ray Diffraction (HRXRD) --- p.14 / Chapter 3.1.1 --- Principal Scattering Geometries --- p.14 / Chapter 3.1.2 --- Strains in the Epitaxial Layer --- p.16 / Chapter 3.1.3 --- Lattice Parameter --- p.21 / Chapter 3.1.4 --- Sb Composition --- p.24 / Chapter 3.1.5 --- Determination of Thickness --- p.24 / Chapter 3.2 --- Photoluminescence (PL) --- p.25 / Chapter 3.2.1 --- Basic Theory of PL --- p.25 / Chapter 3.2.2 --- Strain and Temperature Effect --- p.26 / Chapter 3.2.3 --- Type I and Type II PL --- p.27 / Chapter 3.2.4 --- The Energy Gap of GaAs1-xSbx --- p.28 / Chapter 4. --- RESULTS AND DISCUSSION --- p.31 / Chapter 4.1 --- Direct Analysis of HRXRD Rocking Curves --- p.31 / Chapter 4.1.1 --- GaAs1-xSbx / GaAs Quantum Wells (QWs) --- p.31 / Chapter 4.1.2 --- GaAs1-xSbx /InP Epitaxial Layers --- p.42 / Chapter 4.2 --- Computer Simulation of HRXRD --- p.51 / Chapter 4.2.1 --- Simulation Theory --- p.51 / Chapter 4.2.2 --- Simulation of Rocking Curves --- p.51 / Chapter 4.3 --- Room Temperature PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.66 / Chapter 4.4 --- Low Temperature (LT) PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.75 / Chapter 4.5 --- Excitation Power Dependent (PD) PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.78 / Chapter 4.6 --- Temperature Dependent (TD) PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.85 / Chapter 5. --- CONCLUSIONS --- p.90 / REFERENCES --- p.93

No description available.

Este trabalho teve por objetivo o desenvolvimento de uma metodologia de análise estrutural de heteroestruturas, ou seja, estruturas formadas pela combinação de materiais diferentes depositados em camadas alternadas. O trabalho focalizou aspectos não apenas referentes às técnicas de difração de raios X, comumente utilizadas na caracterização estrutural destes novos materiais, mas também se concentrou no desenvolvimento de cálculos teóricos da intensidade difratada pelos raios X, os quais, comparados com os dados experimentais, dão informação precisa acerca do que poderíamos denominar qualidade estrutural. Uma comparação entre resultados obtidos com a teoria Cinemática Dinâmica foram também explorados e o alcance das duas teorias foi discutido. Este procedimento, embora tenha sido aplicado para a análise de heteroestruturas a base de semicondutores cristalinos, pode também ser aplicado, por exemplo, ao estudo de heteroestruturas magnéticas. É sempre fundamental no processo de desenvolvimento de novos materiais caracterizar as amostras após o crescimento, a fim de comparar os resultados experimentais com os valores nominais obtidos do procedimento de deposição. Em particular, neste trabalho, a caracterização estrutural de super-redes deformadas de Si 1-xGex/Ge e Si/Ge, crescidas sobre substratos de Ge e Si, respectivamente, realizou-se através do uso de técnicas não destrutivas de difração de raios X, envolvendo a medição dos parâmetros próprios das super-redes como: período, número de camadas atômicas, parâmetros de rede e deformação. / The aim of this work was the development of a methodology for the structural analysis of heterostructures, i. e., structures formed by the combination of different materials, deposited as alternate layers. The work focused on aspects not only related to x-ray diffraction techniques, usually utilized for the structural characterization of these new materials, but also it concentrated on the development of theorical calculations of the x-ray diffracted intensity, which were compared with experimental data in order to determine the so-called structural quality. The results obtained with the Kinematical and Dinamical X-ray Diffraction theories were explored and the scope of both theories was discussed. Even though this procedure was applied to the analysis of heterostrutures based on crystalline semiconductors, it also can be used, for example, to the study of magnetic multilayers. It is always fundamental in the development process of new materials to characterize the samples after growth, in order to compare the experimental results with the nominal values obtained by the deposition procedure. ln particular, in this work, the structural characterization of Si1-xGex /Ge and Si/Ge strained superlattices, deposited on Ge and Si substrate, respectively, was performed by means of non-destructive x-ray diffraction techniques, measuring superlattices parameters as: periodicity, number of atomic layers, lattice parameters and strain.

Neste trabalho são calculados os sub-níveis 1s, 2s, 2p±, 3s, 3p± e 3d±2 de elétrons ligados a impurezas doadoras em um poço quântico de GaAs/GaAlAs submetido a um campo magnético uniforme, via método variacional. São calculadas, então, as densidades de estados supondo-se uma distribuição uniforme de doadores, obtendo-se resultados que se assemelham aos do estado fundamental, com um pico principal e outro secundário. De posse do espectro desses sub-níveis rasos são calculados os coeficientes de absorção, na região do infra-vermelho distante, para as transições permitidas fazendo-se o uso da Regra de Ouro de Fermi. As densidades de doadores estão dentro dos limites do modelo de banda de impureza semi-clássica, portanto baixas densidades. Inicialmente é considerada uma compensação nula e uma distribuição uniforme de impurezas. Neste caso os cálculos são realizados analiticamente. Finalmente é considerada a compensação, sendo utilizada a simulação Monte Carlo. Neste segundo processo calcula-se o coeficiente de absorção, primeiramente considerando-se apenas o termo constante da expansão do potencial eletrostático das impurezas ionizadas. Em segunda etapa leva-se em conta os outros termos da expansão e faz-se um tratamento perturbativo. A forma da curva de absorção em infra-vermelho distante levando-se em conta este efeito da compensação é obtido pela primeira vez. São verificados alargamentos não homogêneos nas curvas de absorção e é estudado o efeito da variação da compensação e do campo magnético sobre o coeficiente de absorção. Este estudo constitui um elemento importante para o diagnóstico destas hetero-estruturas semicondutoras. / In this work we obtain the sub-levels 1s, 2s, 2p±, 3s, 3p±, and 3d±2 of donor bound electrons in a GaAs/GaAIAs quantum well by a variational calculation. The densities of states are calculated assuming an uniform distribution of donors, obtaining results similar to that of the ground state, with two peaks, a fundamental and a secundary. We calculate, then, the absorption coefficient, in the far infrared region, by means the Fermi\'s Golden Rule. The densities of donors are within the lirnits of the Semiclassical Impurity Band, i. e., low densities. The calculations are made analiticaly. Finally we consider a non-zero compensation and utilize the Monte Carlo simulation. In this second process the absorption coefficient is calculated firstly considering only the constant term of the expansion of the electroslatic potential due to ionized impurities. Then a perturbative treatement is made with the other terms in the expansion. The shape of the absorption coefficient in the far infrared, with the effect of compensation, was obtained by the first time. Inhomogeneous broadenings appear in the absorptions curves and the effect of variation of compensation and magnetic field is studied. This study is an important element for hetero-structures diagnosis.

In this article, we report an attempt of extending the InGaAsN materials towards 1.3µm and 1.55µm wavelength. All these InGaAsN samples are grown in a plasma-assisted solid-source molecular-beam epitaxy (SS-MBE) system. Our experiments revealed that the nitrides could be grown with both direct nitrogen beam and dispersive nitrogen. The nitrogen incorporation rate could be reduced by the presence of indium flux. The interaction between nitrogen and indium might lead to 3D growth mode and growth dynamics. It is proved that the increasing growth rate reduces the nitrogen incorporation efficiency. The data for nitrogen sticking coefficient are somewhat contradictive. The growth with dispersive nitrogen source causes the improvement of material quality. Fixed indium flux is a better way for the wavelength control. Also, we report some growth optimization work for better PL property and the annealing effect on the samples. Literature is sometimes reviewed for comparison. / Singapore-MIT Alliance (SMA)

Electron transport and relaxation may be substantially different in low-dimensional systems compared to that observed in bulk material. In the present work, Monte Carlo models are used for the solution to the Boltzmann transport equation, with scattering rates calculated quantum mechanically for superlattice and quantum wells. Carrier relaxation following optical excitation is examined in multiple quantum well systems. Simulated results of the carrier relaxation process in coupled asymmetric wells and modulation doped wells are in good agreement with published experimental results on similar structures. Scattering rates in superlattices due to polar optical phonons, intervalley phonons, ionized impurities and carrier-carrier scattering are derived. Carrier transport through high energy superlattice minibands is examined in superlattice base hot electron transistors. Additionally, transport in the ballistic limit in periodic quantum wire structures, including geometric superlattices, is examined utilizing a mode matching method. / Graduation date: 1992

We haved studied the magneto-transport properties of two dimensional electron gas (2DEG) in Si £_-doped In0.22Ga0.78As/AlGaAs single quantum wells ( QWs ) by using Shubnikov-de Haas ( SdH ) measurements . From the SdH measurement , we can clearly observe the SdH oscillations and obtain the SdH frequencies. It indicates the 2DEG in these QWs was confirmed . We also obtain the deep level binding energies¡G 104.4 meV and 9.6 meV for sample 1 and 50.2meV for sample2 by T-dependent Van der Pauw Hall effect measure- ment at magnetic field 0.3T. The difference of these two samples was the In0.1Ga0.9As layer of sample 2 was inserted between In0.22Ga0.78As well and the GaAs spacers . So in this paper , we tried to propose a model to interpret the deep-level traps in the QWs and studied the effect of In0.1Ga0.9As inserted-layer on the In0.22Ga0.78As/GaAs Single Quantum Wells.