Applications Of Inas Gaas Quantum Dot Structure On Optical And Electrical Devices
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Self Assembled Ingaas Gaas Quantum Dots
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Author :
language : en
Publisher: Academic Press
Release Date : 1999-03-29
Self Assembled Ingaas Gaas Quantum Dots written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999-03-29 with Technology & Engineering categories.
This volume is concerned with the crystal growth, optical properties, and optical device application of the self-formed quantum dot, which is one of the major current subjects in the semiconductor research field.The atom-like density of states in quantum dots is expected to drastically improve semiconductor laser performance, and to develop new optical devices. However, since the first theoretical prediction for its great possibilities was presented in 1982, due to the difficulty of their fabrication process. Recently, the advent of self-organized quantum dots has made it possible to apply the results in important optical devices, and further progress is expected in the near future.The authors, working for Fujitsu Laboratories, are leading this quantum-dot research field. In this volume, they describe the state of the art in the entire field, with particular emphasis on practical applications.
Optical Spectroscopy Of Laterally Spaced Inas Gaas Quantum Dot Molecules
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Author : Shilpa Sanwlani
language : en
Publisher:
Release Date : 2010
Optical Spectroscopy Of Laterally Spaced Inas Gaas Quantum Dot Molecules written by Shilpa Sanwlani and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Optical spectroscopy categories.
Over the past decade, potential device applications have fueled an extensive effort to fabricate lateral arrays of quantum dots (QDs) with specific dot densities, spacings and size distributions. An essential element for the further development of QD devices with new functionalities is the introduction of controllable quantum coupling between two or more QDs in such an array. Tunable quantum coupling between vertically stacked InAs QDs has been demonstrated, with the coupling mediated by coherent tunneling and tunable with a static electric field. While these studies have revealed that the spatial arrangement of QDs can lead to remarkable effects, it will be impossible to scale vertical coupling to a large number of QDs. Investigations of lateral quantum coupling have been slower to develop, however, because special growth protocols are required and the ability to independently tune the luminescence energy of separate QDs is lost. Spectroscopy of single pairs of laterally separated QDs is required to resolve the signatures of quantum coupling from inhomogeneously broadened ensemble spectra. Laterally-coupled quantum dots require modified sample preparation methods to isolate single pairs of QDs and apply electric fields that tune the relative energies of the two dots. The electric field must be applied along the surface of the sample, perpendicular to the growth direction. To apply this lateral field, we use interdigitated electrodes patterned onto the sample surface with photolithography and metal deposition. Electrical connections are made to each of the interdigitated top contacts as well as to an ohmic back contact. This three-terminal arrangement makes it possible to independently control both the relative energies of the dots and the charging of the QDs. We present photoluminescence spectra of laterally coupled QDs whose coupling and charge states are tuned with this three-terminal arrangement. We further discuss the implications and opportunities for control of quantum coupling in laterally-scalable architectures.
Indium Gallium Arsenide Quantum Dot Materials For Solar Cell Applications
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Author : Anup Pancholi
language : en
Publisher: ProQuest
Release Date : 2009
Indium Gallium Arsenide Quantum Dot Materials For Solar Cell Applications written by Anup Pancholi and has been published by ProQuest this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Gallium arsenide categories.
The last few years have seen rapid advances in nanoscience and nanotechnology, allowing unprecedented manipulation of nanostructures controlling solar energy capture, conversion, and storage. Quantum confined nanostructures, such as quantum wells (QWs) and quantum dots (QDs) have been projected as potential candidates for the implementation of some high efficiency photovoltaic device concepts, including the intermediate band solar cell (IBSC). In this dissertation research, we investigated multiple inter-related themes, with the main objective of providing a deeper understanding of the physical and optical properties of QD structures relevant to the IBSC concept. These themes are: (i) Quantum engineering and control of energy levels in QDs, via a detailed study of the electronic coupling in multilayer QD structures; (ii) Controlled synthesis of well-organized, good quality, high volume density, and uniform-size QD arrays, in order to maximize the absorption efficiency and to ensure the coupling between the dots and the formation of the minibands; and (iii) Characterization of carrier dynamics and development of techniques to enhance the charge transport and efficient light harvesting. A major issue in a QD-based IBSC is the occurrence of charge trapping, followed by recombination in the dots, which results in fewer carriers being collected and hence low quantum efficiency. In order to collect most of the light-generated carriers, long radiative lifetimes, higher mobilities, and a lower probability of non-radiative recombination events in the solar cell would be desirable. QD size-dependent radiative lifetime and electronic coupling in multilayer QD structures were studied using photoluminescence (PL) and time-resolved photoluminescence (TRPL). For the uncoupled QD structures with thick barriers between the adjacent QD layers, the radiative lifetime was found to increase with the QD size, which was attributed to increased oscillator strength in smaller size dots. On the other hand, in the sample with thin barrier and electronically coupled QDs, the radiative lifetime increases and later decreases with the dot size. This is due to the enhancement of the oscillator strength in the larger size, coherently coupled QDs. In order to improve the quality of multi-layer QD structures, strain compensated barriers were introduced between the QD layers grown on off-oriented GaAs (311)B substrate. The QD shape anisotropy resulted from the growth on off-oriented substrate was studied using polarization-dependent PL measurements both on the surface and the edge of the samples. The transverse electric mode of the edge-emitted PL showed about 5° deviation from the sample surface for the dots grown on (311)B GaAs, which was attributed to the tilted vertical alignment and the shape asymmetry of dots resulted from the substrate orientation. Significant structural quality improvements were attained by introducing strain compensated barriers, i.e., reduction of misfit dislocations and uniform dot size formation. Longer lifetime (~1 ns) and enhanced PL intensity at room temperature were obtained, compared to those in conventional multilayer (In, Ga)As/GaAs QD structures. A significant increase in the open circuit voltage (V oc) was observed for the solar cell devices fabricated with the strain compensated structures. A major issue in a QD IBSC is the occurrence of charge trapping, followed by recombination in the dots, which results in fewer carriers being collected, and hence low quantum efficiency. We proposed and studied a novel structure, in which InAs QDs were sandwiched between GaAsSb (12% Sb) strain-reducing layers (SRLs) with various thicknesses. Both short (~1 ns) and long (~4-6 ns) radiative lifetimes were measured in the dots and were attributed to type-I and type-II transitions, respectively, which were induced by the band alignment modifications at the QD/barrier interface in the structures analyzed, due to the quantum confinement effect resulting from different GaAsSb barrier thicknesses. Based on our findings, a structure with type-II QD/barrier interface with relatively long radiative recombination lifetime may be a viable candidate in designing IBSC.
Quantum Dot Devices
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Author : Zhiming M. Wang
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-05-24
Quantum Dot Devices written by Zhiming M. Wang and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-05-24 with Science categories.
Quantum dots as nanomaterials have been extensively investigated in the past several decades from growth to characterization to applications. As the basis of future developments in the field, this book collects a series of state-of-the-art chapters on the current status of quantum dot devices and how these devices take advantage of quantum features. Written by 56 leading experts from 14 countries, the chapters cover numerous quantum dot applications, including lasers, LEDs, detectors, amplifiers, switches, transistors, and solar cells. Quantum Dot Devices is appropriate for researchers of all levels of experience with an interest in epitaxial and/or colloidal quantum dots. It provides the beginner with the necessary overview of this exciting field and those more experienced with a comprehensive reference source.
Self Assembled Quantum Dots
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Author : Zhiming M Wang
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-11-29
Self Assembled Quantum Dots written by Zhiming M Wang and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-11-29 with Technology & Engineering categories.
This multidisciplinary book provides up-to-date coverage of carrier and spin dynamics and energy transfer and structural interaction among nanostructures. Coverage also includes current device applications such as quantum dot lasers and detectors, as well as future applications to quantum information processing. The book will serve as a reference for anyone working with or planning to work with quantum dots.
Gaas Based Quantum Dot Emitters For Telecomms And Broadband Applications
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Author :
language : en
Publisher:
Release Date : 2011
Gaas Based Quantum Dot Emitters For Telecomms And Broadband Applications written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Quantum Dot Optoelectronic Devices
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Author : Peng Yu
language : en
Publisher: Springer Nature
Release Date : 2020-04-16
Quantum Dot Optoelectronic Devices written by Peng Yu and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-04-16 with Technology & Engineering categories.
This book captures cutting-edge research in semiconductor quantum dot devices, discussing preparation methods and properties, and providing a comprehensive overview of their optoelectronic applications. Quantum dots (QDs), with particle sizes in the nanometer range, have unique electronic and optical properties. They have the potential to open an avenue for next-generation optoelectronic methods and devices, such as lasers, biomarker assays, field effect transistors, LEDs, photodetectors, and solar concentrators. By bringing together leaders in the various application areas, this book is both a comprehensive introduction to different kinds of QDs with unique physical properties as well as their preparation routes, and a platform for knowledge sharing and dissemination of the latest advances in a novel area of nanotechnology.
Optical And Mechanical Investigation Of Inas Gaas Quantum Dots Solar Cells And Inas Nanowires For The Application Of Photovoltaic Device
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Author : Yushuai Dai
language : en
Publisher:
Release Date : 2013
Optical And Mechanical Investigation Of Inas Gaas Quantum Dots Solar Cells And Inas Nanowires For The Application Of Photovoltaic Device written by Yushuai Dai and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Nanowires categories.
"Self-assembled quantum dots (QDs) and nanowires (NWs) are currently the subjects of extensive study due to their promising applications in optoelectronic devices. In order to enhance understanding of the short circuit current improvement in InAs/GaAs quantum dots solar cell (QDSC), the mechanisms of carrier escape by thermal activation and tunneling from InAs quantum dots (QDs) confinements in InAs/GaAs QDSCs are investigated. The fitted activation energy of electrons from temperature dependent photoluminescence (TDPL) is 114 meV. Using this fitted activation energy, calculated thermal escape time and tunneling time of electrons from the ground state of the QDs are 10-12 seconds and 10-6 seconds at 300K, respectively. These results indicate that at room temperature thermal escape is dominant for electrons escape from ground state. At low temperature (8K), tunneling mainly affects the electrons escape from ground state, since thermal energy cannot support electrons to overcome the fitted activation energy (barrier, 114 meV). In addition, in order to describe the new physics and achieve the final success in nanowire device for photovoltaic applications, the first step is to develop high-quality semiconductor nanowires on the selected substrate. Morphological and crystal structure characterizations were performed via SEM and TEM for InAs nanowire samples grown with and without Au seed on GaAs substrate using metal organic vapor phase expitaxy (MOVPE). Several major factors affect the NW growth in terms of shape, density, etc. For nanowire growth with Au seed, its growth direction mainly depends on the substrate, while its uniformity is initially related to the Au seed coverage. III/V ratio affects the NW aspect ratio (length/bottom width), ranged from 12.00 to 38.93. Increasing temperature accelerates the growth rate in both axial and radial directions. NWs grown without Au seed using a pattern mask show no tapering along the growth direction with an average diameter of 26 nm. All defects stop in the buffer layer when InAs nanowires grown with an Au seed, but a mix of ZB and WZ crystal phases were observed along the growth direction of nanowire. InAs NWs grown without Au seeds also show a mixture of different crystal phases along the growth direction. The diameter of InAs nanowire should be further reduced to 3-6 nm as to achieve PL response between 1000~1300 nm."--Abstract.
Single Quantum Dots
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Author : Peter Michler
language : en
Publisher: Springer Science & Business Media
Release Date : 2003-12-09
Single Quantum Dots written by Peter Michler and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-12-09 with Science categories.
Special focus is given to the optical and electronic properties of single quantum dots due to their potential applications in devices operating with single electrons and/or single photons. This includes quantum dots in electric and magnetic fields, cavity-quantum electrodynamics, nonclassical light generation, and coherent optical control of excitons.
Semiconductor Quantum Dots
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Author : Yasuaki Masumoto
language : en
Publisher: Springer Science & Business Media
Release Date : 2002-05-28
Semiconductor Quantum Dots written by Yasuaki Masumoto and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002-05-28 with Science categories.
Growth of Self Organized Quantum Dots / J.-S. Lee / - Excitonic Structures and Optical Properties of Quantum Dots / Toshihide Takagahara / - Electron-Phonon Interactions in Semiconductor Quantum Dots / Toshihide Takagahara / - Micro-Imaging and Single Dot Spectroscopy of Self Assembled Quantum Dots / Mitsuru Sugisaki / - Persistent Spectral Hole Burning in Semiconductor Quantum Dots / Yasuaki Masumoto / - Dynamics of Carrier Relaxation in Self Assembled Quantum Dots / Ivan V. Ignatiev, Igor E. Kozin / - Resonant Two-Photon Spectroscopy of Quantum Dots / Alexander Baranov / - Homogeneous Width of Confined Excitons in Quantum Dots - Experimental / Yasuaki Masumoto / - Theory of Exciton Dephasing in Semiconductor Quantum Dots / Toshihide Takagahara / - Excitonic Optical Nonlinearity and Weakly Correlated Exciton-Pair States / Selvakumar V. Nair, Toshihide Takagahara / - Coulomb Effects in the Optical Spectra of Highly Excited Semiconductor Quantum Dots / Selvakumar V. Nair / - Device ...