Download or read book Optical and electronic properties of single laterally coupled In Ga As GaAs quantum dot molecules written by Matthias Michael Heldmaier and published by . This book was released on 2013 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical Properties of Single Charge tunable and Laterally Coupled In Ga As GaAs Quantum Dots written by Claus Hermannstädter and published by . This book was released on 2010 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical and Electrical Properties of Single Self Assembled Quantum Dots in Lateral Electric Fields written by Malte Huck and published by diplom.de. This book was released on 2010-03-25 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inhaltsangabe:Abstract: Chapter 1: In this thesis we investigate the optical properties of self-assembled quantum dots exposed to a lateral electric field. As a result of the electric field the wave functions of electrons and holes inside the quantum dot are manipulated, which makes it possible to tune their energy levels and control the optical properties of the system. The possibility of tuning the emission energy of different few particle states using this method makes this system very promising for the use of a source of polarization entangled photons as discussed in the following sections. In Section 1.1 the concept of entangled states is introduced together with a brief historical overview. The possibility of using the exciton biexciton cascade of a self-assembled quantum dot for the generation of entangled photon pairs is presented in Section 1.2. Chapter 2: In this chapter we introduce the concept of quantum dots and demonstrate their optical emission properties. In Section 2.1 the quantum dot is introduced as a three-dimensional charge carrier trap. Several types of quantum dots are presented in an overview. In Section 2.2 we discuss the physical effects that occur on the way from bulk semiconductor material to the three-dimensional charge carrier confinement in the case of quantum dots. The growth of self-assembled quantum dot samples is the topic of Section 2.3, where the technique of molecular beam epitaxy is introduced (Section 2.3.1). This technique is used to grow the semiconductor quantum dots via heteroepitaxy in the Stranski-Krastanov growth mode (Section 2.3.2). Quantum dots are commonly referred to as artificial atoms due to their atomlike emission features. The origin for this expression is explained in Section 2.4 on the basis of the energetic structure of self-assembled quantum dots. The optical properties of quantum dots are discussed in Section 2.5, beginning with an introduction to the experimental setup that has been used to investigate the quantum dots during this thesis (Section 2.5.1). Different optical excitation modes are presented in Section 2.5.2 and in Section 2.5.3 we discuss, how to achieve a low enough quantum dot density on the analyzed samples. Section 2.5.4 deals with the photoluminescence of different exciton states and in Section 2.5.5 we present how these lines can be identified via power dependent measurements. Finally, the concept of initial charges in self-assembled quantum dots is presented in [...]
Download or read book Influence of Barrier Layer on Optical and Electronic Properties of Quantum Dot Molecules written by Prasoon Pancholi and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, it was suggested that the performance of nanostructure-based optoelectronic devices, in particular quantum dot-based devices, may be enhanced when the active region of the device consists of dots that are coupled laterally and/or vertically. The electronic coupling between the dots provides a new degree of freedom in engineering the electronic bandstructure of the nanostructures. For example, strong electronic coupling between two dots defines a new entity, known as a quantum dot molecule (QDM). We provide in this thesis a comparative theoretical and experimental study of structures consisting of two layers of vertically coupled InAs/GaAs QDs, grown by molecular beam epitaxy on (001) GaAs substrates, in which the GaAs barrier layer thickness was varied between 4 and 10 nm, thus insuring very strong coupling between the dot layers and the existence of "molecule-like" behavior. Theoretically, to understand the nature of the electronic and optical properties of the self-assembled dots and molecules, we determined the strain distribution in the dots. The strain effects were included via the deformation potential theory in an eight-band k p model to calculate the respective electronic band structures. Our experimental investigations of the optical and structural properties of QDM structures confirm the formation of QDMs with energy splittings that agree well with the results of our calculations.
Download or read book Single Quantum Dots written by Peter Michler and published by Springer Science & Business Media. This book was released on 2003-12-09 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book On the Interactions Between Charges Phonons and Photons in Electric Field Tunable Quantum Dot Molecules written by and published by . This book was released on 2001 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the optical properties of single InAs/GaAs quantum dot molecules. A quantum dot molecule consists of a pair of quantum dots coupled by a nanometer scale tunneling barrier. Compared to single quantum dots, quantum dot molecules provide greatly enhanced versatility - with the ease of an electric field control, one gains broad flexibility to tune electronic energy levels and manipulate particle tunneling within a QDM. As a consequence, individual QDMs are being intensely studied as controllable interfaces of charge, spin and photonic quantum states at the single particle level. On the other hand, phonons - the quantized vibrations of the underlying crystal lattice - have mostly been left outside the realm of coherent control. In the domain of solid-state quantum technologies, the ubiquitous phonons are mainly considered for the limitations they impose. Omnipresent electron-phonon interactions and the predominantly dissipative nature of phonons are typically a major source of decoherence of the atom-like quantum states hosted by low-dimensional solid-state structures, such as QDMs. Here, we report experimental and theoretical results on the interactions between charges, photons and phonons in electric field tunable quantum dot molecules. Using an effective mass perturbation model, we compute the low energy biexciton states of a quantum dot molecule and apply them to provide a theoretical description of the dipole-dipole interaction between two excitons occupying separate dots in a quantum dot molecule. The expected properties of these so called dipolar states are presented, and we highlight their potential application as a switch for manipulating the transition energy and tunneling properties of the ground state neutral exciton. We then present results from a comprehensive investigation of the quantum confined Stark effect in quantum dot molecules, in which we studied the electric-field dependent energy shifts of exciton states as a function of the tunneling barrier width. Our experimental and computational results reveal that molecular wavefunction formation in quantum dot molecules strongly affects the quantum confined Stark effect, even as the dots are tuned far from resonance for particle tunneling. This dissertation culminates with our report of a novel mechanism by which phonons are made non-dissipative and coherent via electric field control and the optically driven formation of a molecular polaron in a quantum dot molecule. The coherent interaction of a single optical phonon with individual electronic states is revealed via a Fano-type quantum interference that produces a phonon-induced transparency in the optical absorption of individual quantum dot molecules. Experimentally, we find that the transparency is widely tunable by electronic and optical means, and provides a mechanism for amplifying weak coupling channels. This work is significant in that it demonstrates a specific mechanism by which typically incoherent and dissipative phonons are made to behave in a coherent and non-dissipative manner. As such, we demonstrate that phonons may enter the realm of mutual control of quantum states on the single particle level, which so far has been dominated by photons, electrons and spins.
Download or read book Self Assembled InGaAs GaAs Quantum Dots written by and published by Academic Press. This book was released on 1999-03-29 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Exploring Single Hole States in InAs GaAs Quantum Dots and Quantum Dot Molecules Under 2 D Electric Fields written by Xiangyu Ma and published by . This book was released on 2019 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: InAs/GaAs quantum dots (QDs) and quantum dot molecules (QDMs) are self-assembled semiconductor nanostructures that can trap a single electron or hole in a 3-D potential-well. Grown by molecular beam epitaxy (MBE), they have excellent optical qualities that can be used in applications for quantum information processing and quantum computing. Specifically, hole spins in a single QD/QDM have longer decoherence time than electron spins due to the lack of hyperfine interaction, making hole spins a great qubit candidate. However, many challenges such as QD growth, device integration, and spin manipulation inhibit the scalability of a hole-spin-based quantum information platform. A deeper understanding of the hole spin physics and the QD/QDM material system is needed to advance device engineering opportunities.
Download or read book Semiconductor Macroatoms written by Fausto Rossi and published by World Scientific. This book was released on 2005 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the basic physics of semiconductor macroatoms at the nanoscale as well as their potential application as building blocks for the realization of new-generation quantum devices.It provides a review on state-of-the art fabrication and characterization of semiconductor quantum dots aimed at implementing single-electron/exciton devices for quantum information processing and communication. After an introductory chapter on the fundamentals of quantum dots, a number of more specialized review articles presents a comprehensive picture of this rapidly developing field, specifically including strongly multidisciplinary topics such as state-of-the-art nanofabrication and optical characterization, fully microscopic theoretical modeling of nontrivial many-body processes, as well as design and optimization of novel quantum-device architectures.Sample Chapter(s)
Download or read book Molecular Beam Epitaxy written by Mohamed Henini and published by Newnes. This book was released on 2012-12-31 with total page 745 pages. Available in PDF, EPUB and Kindle. Book excerpt: This multi-contributor handbook discusses Molecular Beam Epitaxy (MBE), an epitaxial deposition technique which involves laying down layers of materials with atomic thicknesses on to substrates. It summarizes MBE research and application in epitaxial growth with close discussion and a 'how to' on processing molecular or atomic beams that occur on a surface of a heated crystalline substrate in a vacuum.MBE has expanded in importance over the past thirty years (in terms of unique authors, papers and conferences) from a pure research domain into commercial applications (prototype device structures and more at the advanced research stage). MBE is important because it enables new device phenomena and facilitates the production of multiple layered structures with extremely fine dimensional and compositional control. The techniques can be deployed wherever precise thin-film devices with enhanced and unique properties for computing, optics or photonics are required. This book covers the advances made by MBE both in research and mass production of electronic and optoelectronic devices. It includes new semiconductor materials, new device structures which are commercially available, and many more which are at the advanced research stage. - Condenses fundamental science of MBE into a modern reference, speeding up literature review - Discusses new materials, novel applications and new device structures, grounding current commercial applications with modern understanding in industry and research - Coverage of MBE as mass production epitaxial technology enhances processing efficiency and throughput for semiconductor industry and nanostructured semiconductor materials research community
Download or read book Compound Semiconductors 1996 Proceedings of the Twenty Third INT Symposium on Compound Semiconductors held in St Petersburg Russia 23 27 September 1996 written by M.S. Shur and published by CRC Press. This book was released on 2020-10-28 with total page 1087 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing a comprehensive overview of developments to both the academic and industrial communities, Compound Semiconductors 1996 covers all types of compound semiconducting materials and devices. The book includes results on blue and green lasers, heterostructure devices, nanoelectronics, and novel wide band gap semiconductors. With invited review papers and research results in current topics of interest, this volume is part of a well-known series of conferences for the dissemination of research results in the field.
Download or read book Physics of Quantum Rings written by Vladimir M. Fomin and published by Springer Science & Business Media. This book was released on 2013-08-29 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with a new class of materials, quantum rings. Innovative recent advances in experimental and theoretical physics of quantum rings are based on the most advanced state-of-the-art fabrication and characterization techniques as well as theoretical methods. The experimental efforts allow to obtain a new class of semiconductor quantum rings formed by capping self-organized quantum dots grown by molecular beam epitaxy. Novel optical and magnetic properties of quantum rings are associated with non-trivial topologies at the nanoscale. An adequate characterization of quantum rings is possible on the basis of modern characterization methods of nanostructures, such as Scanning Tunneling Microscopy. A high level of complexity is demonstrated to be needed for a dedicated theoretical model to adequately represent the specific features of quantum rings. The findings presented in this book contribute to develop low-cost high-performance electronic, spintronic, optoelectronic and information processing devices based on quantum rings.
Download or read book Comprehensive Semiconductor Science and Technology written by and published by Newnes. This book was released on 2011-01-28 with total page 3572 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductors are at the heart of modern living. Almost everything we do, be it work, travel, communication, or entertainment, all depend on some feature of semiconductor technology. Comprehensive Semiconductor Science and Technology, Six Volume Set captures the breadth of this important field, and presents it in a single source to the large audience who study, make, and exploit semiconductors. Previous attempts at this achievement have been abbreviated, and have omitted important topics. Written and Edited by a truly international team of experts, this work delivers an objective yet cohesive global review of the semiconductor world. The work is divided into three sections. The first section is concerned with the fundamental physics of semiconductors, showing how the electronic features and the lattice dynamics change drastically when systems vary from bulk to a low-dimensional structure and further to a nanometer size. Throughout this section there is an emphasis on the full understanding of the underlying physics. The second section deals largely with the transformation of the conceptual framework of solid state physics into devices and systems which require the growth of extremely high purity, nearly defect-free bulk and epitaxial materials. The last section is devoted to exploitation of the knowledge described in the previous sections to highlight the spectrum of devices we see all around us. Provides a comprehensive global picture of the semiconductor world Each of the work's three sections presents a complete description of one aspect of the whole Written and Edited by a truly international team of experts
Download or read book Quantum Dot Molecules written by Jiang Wu and published by Springer Science & Business Media. This book was released on 2013-10-28 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: A quantum dot molecule (QDM) is composed of two or more closely spaced quantum dots or “artificial atoms.” In recent years, QDMs have received much attention as an emerging new artificial quantum system. The interesting and unique coupling and energy transfer processes between the “artificial atoms” could substantially extend the range of possible applications of quantum nanostructures. This book reviews recent advances in the exciting and rapidly growing field of QDMs via contributions from some of the most prominent researchers in this scientific community. The book explores many interesting topics such as the epitaxial growth of QDMs, spectroscopic characterization, and QDM transistors, and bridges between the fundamental physics of novel materials and device applications for future information technology. Both theoretical and experimental approaches are considered. Quantum Dot Molecules can be recommended for electrical engineering and materials science department courses on the science and design of advanced and future electronic and optoelectronic devices.
Download or read book Electrical Electronics Abstracts written by and published by . This book was released on 1997 with total page 1904 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Functionalization of Resonant Interactions in Coupled Quantum Dots written by and published by . This book was released on 2017 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this dissertation is discovering and finding functional uses of resonant interactions that occur in coupled quantum dots (i.e. quantum dot molecules, QDMs). Coupled quantum dots compared to individual quantum dots offer a more versatile platform to study interactions between photons, charges, and phonons. Applying an electric field in a QDM system allows tuning of the electronic energy states and controls particle tunneling between quantum dots, thus coupling the quantum dots. For the past two decades, extensive research into coupled quantum dot systems has led to a deeper understanding and control of the charge, spin and photonic properties of single quantum states. This dissertation continues the pursuit to further understand these QDM systems with a particular emphasis on exploring the physics of resonant interactions between electronic states, phononic states, and optical transitions. This work consists of three components, the first is a novel experimental method that is capable of achieving high resolution spectra. The second addresses the resonant interaction between discrete neutral exciton and optical phonons that generates a molecular polaron, which can be tuned to render QDM emissions transparent or amplify weak transitions. The final component addresses ultrafast optical charging into specific charge states of a QDM. In the first research chapter we report on an optical spectroscopy method which is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots using a standard, easy to use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser linewidth limited resolution with multi-channel photoluminescence detection. Using this method allows the ability of greatly improving the resolution beyond that of a common single stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonons allow us to separate and filter out the elastically scattered excitation laser light. An advantageous feature of this method is that it is easily incorporated into standard spectroscopy set-ups, being accessible to a number of researchers. In the second research chapter we report on the coherent interaction between photons and phonons mediated by quantum dot molecular excitons. Fano resonances occur between an indirect discrete state and the optical phonon band's continuum of states. This quantum interference is highly tunable with excitation energy and laser power and allows for the phonons to behave in a coherent and non-dissipative manner. This feature has led to rendering QDM optical transitions transparent and can alternately be used to amplify weak coupling channels. This finding, using phonons in a coherent manner, can lead to new technologies in the emerging field of phononics. In the third research chapter we report on optical charging of quantum dot molecules. The excited state spectra of the neutral and singly charged excitons in QDMs are being studied via photoluminescence excitation spectroscopy (PLE). We find an anti-correlated behavior of the resonances in the PLE spectra of different charge states, allowing for selective optical charging of the QDMs. The PLE spectra are analyzed across the regions of resonances between the indirect exciton and excited direct transitions of the low energy dot of the dot pair. The charging process seen in the excited state spectra of the trion and neutral exciton is explained by the competition between various transition rates at the resonance between the two charge states. These distinct resonances are examples of optical charging and de-charging process within the QDM. We present the experimental results and mathematical model describing this charging process.
Download or read book Optical and Electronic Properties of In Ga As Self assembled Quantum Dots written by 張峻瑋 and published by . This book was released on 2003 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
