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Optical and Electrical Properties of Single Self-Assembled Quantum Dots in Lateral Electric Fields

Optical and Electrical Properties of Single Self-Assembled Quantum Dots in Lateral Electric Fields PDF Author: Malte Huck
Publisher: diplom.de
ISBN: 3836644398
Category : Science
Languages : en
Pages : 137

Book Description
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 [...]

Optical and Electrical Properties of Single Self-Assembled Quantum Dots in Lateral Electric Fields

Optical and Electrical Properties of Single Self-Assembled Quantum Dots in Lateral Electric Fields PDF Author: Malte Huck
Publisher: diplom.de
ISBN: 3836644398
Category : Science
Languages : en
Pages : 137

Book Description
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 [...]

Single Quantum Dots

Single Quantum Dots PDF Author: Peter Michler
Publisher: Springer Science & Business Media
ISBN: 9783540140221
Category : Science
Languages : en
Pages : 370

Book Description
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.

Quantum Dot Heterostructures

Quantum Dot Heterostructures PDF Author: Dieter Bimberg
Publisher: John Wiley & Sons
ISBN: 9780471973881
Category : Science
Languages : en
Pages : 350

Book Description
Da die Nachfrage nach immer schnelleren und kleineren Halbleiterbauelementen stetig wächst, sind Quanten-Dots und -Pyramiden rasant in den Mittelpunkt der Halbleiterforschung gerückt. Dieses Buch vermittelt einen umfassenden Überblick über den aktuellen Forschungsstand auf diesem Gebiet. Behandelt werden u.a. Fragen, wie Strukturen aufgebaut, wie sie charakterisiert werden und wie sie die Leistungsfähigkeit der Bauelemente bestimmen. (11/98)

Single Quantum Dots

Single Quantum Dots PDF Author: Peter Michler
Publisher: Springer
ISBN: 9783662307861
Category : Technology & Engineering
Languages : en
Pages : 352

Book Description
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

Semiconductor Quantum Dots PDF Author: Yasuaki Masumoto
Publisher: Springer Science & Business Media
ISBN: 9783540428053
Category : Science
Languages : en
Pages : 520

Book Description
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 ...

Self-Assembled InGaAs/GaAs Quantum Dots

Self-Assembled InGaAs/GaAs Quantum Dots PDF Author:
Publisher: Academic Press
ISBN: 0080864589
Category : Technology & Engineering
Languages : en
Pages : 385

Book Description
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.

Electronic, Optical and Magnetic Properties of Self-assembled Quantum Dots Containing Magnetic Ions

Electronic, Optical and Magnetic Properties of Self-assembled Quantum Dots Containing Magnetic Ions PDF Author: Anna Trojnar
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Book Description
There is currently interest in developing control over the spin of a single Manganese (Mn) ion, the atomic limit of magnetic memory, in semiconductor quantum dots (QDs). In this work we present theoretical results showing how one can manipulate the spin of Mn ion with light in a QD by engineering Mn-multi-exciton interactions through quantum interference, design of exciton and bi-exciton states and application of the magnetic field. We develop a fully microscopic model of correlated exciton and bi-exciton interacting with the Mn ion. The electrons and heavy holes, confined in the QD, approximated as a two-dimensional harmonic oscillator (HO), interact via direct and short- and long-range exchange Coulomb interactions. The matrix elements of the exchange interaction are computed for the first time in the harmonic oscillator basis and for arbitrary magnetic fields. The exciton and bi-exciton energies and states are computed using the configuration interaction method. The interaction between carriers and the Mn spin is accounted for by the Heisenberg electron-Mn and Ising hole-Mn exchange interactions. For a single exciton confined in a magnetic dot, a novel quantum interference (QI) effect between the electron-hole Coulomb scattering and the scattering by Mn ion is obtained. The QI significantly affects the exciton-Mn coupling, modifying the splitting of the emission/absorption lines from the exciton-Mn complex depending on the degree of electronic correlations in the exciton state. The second signature of the QI are the nonuniform energy gaps between the consecutive emission peaks due to the scattering of carriers by Mn among single-particle orbitals. Magneto-photoluminescence experiments show that the coupling between the exciton and Mn ion does not change in the magnetic field. We report that electron-hole correlations counteract the magnetic squeezing of the single-particle wave functions strengthening the carrier-Mn interactions. As a result, the rate of change of the magneto-photoluminescence spectra with magnetic field is reduced as observed in the experiment. We develop here for the first time a microscopic theory of bi-exciton-Mn complex, and report the presence of the fine structure of bi-exciton-Mn complex, even though as a spin-singlet it is expected to decouple from the localized spin. Theoretical results are compared with experiments in Grenoble and Warsaw.

Photodetectors

Photodetectors PDF Author: Bahram Nabet
Publisher: Woodhead Publishing
ISBN: 0081028768
Category : Science
Languages : en
Pages : 516

Book Description
Every bit of information that circulates the internet across the globe is a pulse of light, that at some point will need to be converted to an electric signal in order to be processed by the electronic circuitry in our data centers, computers, and cell phones. Photodetectors (PD’s) perform this conversion with ultra high speed and efficiency, in addition to being ubiquitously present in many other devices ranging from the mundane TV remote controls, to ultra high resolution instrumentation used in Laser Interferometer Gravitational Wave Observatory (LIGO) that reach the edge of the universe and measure gravitational waves. The second edition of "Photodetectors" fully updates the popular first edition with updated information covering the state-of-the-art in modern photodetectors. The 2nd edition starts with basic metrology of photodetectors and common figures-of-merit to compare various devices. It follows with chapters that discuss single-photon detection with Avalanche Photodiodes; organic photodetectors that can be inkjet printed; and silicon-germanium PDs popular in burgeoning field of Silicon Photonics. Internationally recognized experts contribute chapters on one-dimensional, nanowire, PDs as well as high speed zero-dimensional, quantum dot, versions that increase the spectral span as well as speed and sensitivity of PDs and can be produced on various substrates. Solar-blind PDs that operate in harsh environments such as deep space, or rocket engines, are reviewed and new devices in GaN technology . Novel Plasmonic PDs, as well as devices which employ micro-plasma of confined charge in order to make devices that overcome speed limitation of transfer of electronic charge, are covered in other chapters. Using different, novel technologies, CMOS compatible devices are described in two chapters, and ultra high speed PDs that use low-temperature-grown GaAs (LT-GaAs) to detect fast THz signals are reviewed in another chapter. Photodetectors used in application areas of Silicon-Photonics and Microwave-Photonics are reviewed in final chapters of this book. All chapters are of a review nature, providing a perspective of the field before concentrating on particular advancements. As such, the book should appeal to a wide audience that ranges from those with general interest in the topic, to practitioners, graduate students and experts who are interested in the state-of-the-art in photodetection. Addresses various photodetector devices from ultra high speed to ultra high sensitivity, capable of operation in harsh environments Considers a range of applications for this important technology, including silicon photonics and photonic integrated circuits Includes discussions of detectors based on reduced dimensional systems such as quantum wells, nanowires, and quantum dots, as well as travelling wave, and plasmonic detectors

Quantum Dots

Quantum Dots PDF Author: Lucjan Jacak
Publisher: Springer Science & Business Media
ISBN: 3642720021
Category : Technology & Engineering
Languages : en
Pages : 176

Book Description
We present an overview of the theoretical background and experimental re sults in the rapidly developing field of semiconductor quantum dots - systems 8 6 of dimensions as small as 10- -10- m (quasi-zero-dimensional) that contain a small and controllable number (1-1000) of electrons. The electronic structure of quantum dots, including the energy quan tization of the single-particle states (due to spatial confinement) and the evolution of these (Fock-Darwin) states in an increasing external magnetic field, is described. The properties of many-electron systems confined in a dot are also studied. This includes the separation of the center-of-mass mo tion for the parabolic confining potential (and hence the insensitivity of the transitions under far infrared radiation to the Coulomb interactions and the number of particles - the generalized Kohn theorem) and the effects due to Coulomb interactions (formation of the incompressible magic states at high magnetic fields and their relation to composite jermions), and finally the spin-orbit interactions. In addition, the excitonic properties of quantum dots are discussed, including the energy levels and the spectral function of a single exciton, the relaxation of confined carriers, the metastable states and their effect on the photoluminescence spectrum, the interaction of an exciton with carriers, and exciton condensation. The theoretical part of this work, which is based largely on original re sults obtained by the authors, has been supplemented with descriptions of various methods of creating quantum-dot structures.

Semiconductor Quantum Dots

Semiconductor Quantum Dots PDF Author: Ladislaus Alexander Banyai
Publisher: World Scientific
ISBN: 9814504238
Category : Science
Languages : en
Pages : 264

Book Description
Semiconductor Quantum Dots presents an overview of the background and recent developments in the rapidly growing field of ultrasmall semiconductor microcrystallites, in which the carrier confinement is sufficiently strong to allow only quantized states of the electrons and holes. The main emphasis of this book is the theoretical analysis of the confinement induced modifications of the optical and electronic properties of quantum dots in comparison with extended materials. The book develops the theoretical background material for the analysis of carrier quantum-confinement effects, introduces the different confinement regimes for relative or center-of-mass motion quantization of the electron-hole-pairs, and gives an overview of the best approximation schemes for each regime. A detailed discussion of the carrier states in quantum dots is presented and surface polarization instabilities are analyzed, leading to the self-trapping of carriers near the surface of the dots. The influence of spin-orbit coupling on the quantum-confined carrier states is discussed. The linear and nonlinear optical properties of small and large quantum dots are studied in detail and the influence of the quantum-dot size distribution in many realistic samples is outlined. Phonons in quantum dots as well as the influence of external electric or magnetic fields are also discussed. Last but not least the recent developments dealing with regular systems of quantum dots are also reviewed. All things included, this is an important piece of work on semiconductor quantum dots not to be dismissed by serious researchers and physicists.