FINGERPRINTS IN THE OPTICAL AND TRANSPORT PROPERTIES OF QUANTUM DOTS Edited by Ameenah Al-Ahmadi Fingerprints in the Optical and Transport Properties of Quantum Dots Edited by Ameenah Al-Ahmadi Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2012 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Molly Kaliman Technical Editor Teodora Smiljanic Cover Designer InTech Design Team First published June, 2012 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechopen.com Fingerprints in the Optical and Transport Properties of Quantum Dots, Edited by Ameenah Al-Ahmadi p. cm. ISBN 978-953-51-0648-7 Contents Preface IX Section 1 Optical Properties of Quantum Dot Systems 1 Chapter 1 InAs Quantum Dots of Engineered Height for Fabrication of Broadband Superluminescent Diodes 3 S. Haffouz and P.J. Barrios Chapter 2 Influence of Optical Phonons on Optical Transitions in Semiconductor Quantum Dots 29 Cheche Tiberius and Emil Barna Chapter 3 Temperature-Dependent Optical Properties of Colloidal IV-VI Quantum Dots, Composed of Core/Shell Heterostructures with Alloy Components 63 Efrat Lifshitz, Georgy I. Maikov, Roman Vaxenburg, Diana Yanover, Anna Brusilovski, Jenya Tilchin and Aldona Sashchiuk Chapter 4 Optical Properties of Spherical Colloidal Nanocrystals 91 Giovanni Morello Chapter 5 Molecular States of Electrons: Emission of Single Molecules in Self-Organized InP/GaInP Quantum Dots 125 Alexander M. Mintairov, James L. Merz and Steven A. Blundell Chapter 6 InAs Quantum Dots in Symmetric InGaAs/GaAs Quantum Wells 153 Tetyana V. Torchynska Chapter 7 Photoionization Cross Sections of Atomic Impurities in Spherical Quantum Dots 181 C.Y. Lin and Y.K. Ho Chapter 8 Exciton States in Free-Standing and Embedded Semiconductor Nanocrystals 199 Yuriel Núñez Fernández, Mikhail I. Vasilevskiy, Erick M. Larramendi and Carlos Trallero-Giner Chapter 9 In-Gap State of Lead Chalcogenides Quantum Dots 219 Xiaomei Jiang Chapter 10 Exciton Dynamics in High Density Quantum Dot Ensembles 231 Osamu Kojima Section 2 Transport and Eletronics Properties of Quantum Dot Systems 245 Chapter 11 Electron Transport Properties of Gate-Defined GaAs/Al x Ga 1-x As Quantum Dot 247 Dong Ho Wu and Bernard R. Matis Chapter 12 Tunneling Atomic Force Microscopy of Self-Assembled In(Ga)As/GaAs Quantum Dots and Rings and of GeSi/Si(001) Nanoislands 273 Dmitry Filatov, Vladimir Shengurov, Niyaz Nurgazizov, Pavel Borodin and Anastas Bukharaev Chapter 13 Quantum Injection Dots 299 Eliade Stefanescu Chapter 14 Quantum Mechanics of Semiconductor Quantum Dots and Rings 333 I. Filikhin, S.G. Matinyan and B. Vlahovic Chapter 15 Non-Equilibrium Green Functions of Electrons in Single-Level Quantum Dots at Finite Temperature 371 Nguyen Bich Ha Chapter 16 Electron Scattering Through a Quantum Dot 401 Leonardo Kleber Castelano, Guo-Qiang Hai and Mu-Tao Lee Chapter 17 Coherent Spin Dependent Transport in QD-DTJ Systems 425 Minjie Ma, Mansoor Bin Abdul Jalil and Seng Ghee Tan Chapter 18 The Thermopower of a Quantum Dot Coupled to Luttinger Liquid System 447 Kai-Hua Yang, Yang Chen, Huai-YuWang and Yan-JuWu Preface Quantum dots are one of the most promising types of nanoparticles, which are exceptionally useful for variety of new applications because of their unique properties. This is a collaborative book sharing and providing the academic community with a base text that could serve as a reference in research by presenting up-to-date research work on the field of quantum dot systems. We are most grateful to all authors of the chapters for highlighting the important issue of the potential applications of quantum dot system with a high quality work of their research. We are especially thankful for the cooperation and support from InTech team who helped in publishing this book, in particular the publishing process manager of this book, Ms. Molly Kaliman for her hard effort and patience during the process of publishing the book. “To my son Azuz” Ameenah N. Al-Ahmadi, PhD Associate Professor of Physics Faculty of Apllied Science, Umm Al-Qura University, KSA [...]... used in these studies were 2Å/s and 0.23Å/s, respectively The epitaxial growth procedure of the InAs QDs on GaAs buffer was performed as following: after growing the 200nm GaAs buffer layer at 600ºC, the substrate (a) (b) (c) (d) Fig 3 Schematic drawing of the evolution of the dots during the overgrowth of the InAs with GaAs capping layer 12 Fingerprints in the Optical and Transport Properties of Quantum. .. and its corresponding peak wavelength as a function of the injection current The enhancement of the 3dBbandwith and the continuous blue-shift of the corresponding peak wavelength with increasing injection current from 2mA to 700mA are attributed to the progressive increase of contribution of all dots to the emission mechanism At a low injection current, the carriers 20 Fingerprints in the Optical and. .. and Transport Properties of Quantum Dots excited in small dots, which have smaller exciton localization energies, may escape out of the dots and transfer to the large ones, and then radiate When increasing the injection current, GS in larger dots become occupied, thus reducing the transfer of carriers between isolated dots The energy states of small dots then begin to be filled and the shape of the. .. region of the SLDs where the dot height was varied by controlling the thickness of the GaAs cap layers deposited at low temperature The arrows indicate the position where the indium-flush was executed (dx) l4 is the height of the dots in layer 4 (b) Schematic diagram of the photoluminescence (PL) spectrum of such a stack of quantum dots InAs Quantum Dots of Engineered Height for Fabrication of Broadband... engineering the gain spectrum of the quantum dots- based superluminescent diodes will be summarized in the third section of this chapter Our approach for engineering the bandwidth of multiple stacks of InAs/GaAs QDs will be presented in the fourth section and demonstration of an ultra wide broadband InAs/GaAs quantum- dot superluminescent diodes (QD-SLDs) will be then reported in the last section of. .. factor of 100) and the central peak was blueshifted by 31meV The spectra broadening in the case of S3 and S4 can be explained by the lateral coupling between the dots, the GS emission from the small dots overlapping with the emission from larger dots However, the noticeable reduction in the PL intensity in S4 was related to the formation of defective dots when their density was increased For broadband... to 53nm at injection current of 1600mA As it can be seen from Fig 16(b), the bandwidth narrowing above an injection current of 700mA corresponds well to the injection 24 Fingerprints in the Optical and Transport Properties of Quantum Dots current range where the superlinear behavior was observed in L-I curves in Fig 15 This bandwidth narrowing is caused by the disproportionate increase in gain for different... of different areal densities, capped with 100nm GaAs layers 14 Fingerprints in the Optical and Transport Properties of Quantum Dots 4.3 Height engineering of self-assembled InAs/GaAs QDs for wideband emission The indium-flush process is a very reproducible and predictable process to engineer the QD height and is therefore a reliable tool for tuning the QD emission energy By varying the thickness of. .. Increasing further the bandwidth of the emission spectrum of the SLDs is a complicated process and requires more than just optimization of the growth conditions of the active region of the device The precise control of the average size distribution of the dots within one layer is a very challenging process and is very difficult to reproduce Very practical and successful ideas based on engineering the. .. half maximum of the SLDs output spectrum of the In0 .7Ga0.3As/GaAs quantum dot system, with a standard deviation in the average size of the QD ensemble of 10%, can be as high as 140nm Increasing further the size variation of the dots to 30% should result in bandwidth as high as 160nm The confinement potential between the dots and the barriers is another important factor for modifying the spectral width . FINGERPRINTS IN THE OPTICAL AND TRANSPORT PROPERTIES OF QUANTUM DOTS Edited by Ameenah Al-Ahmadi Fingerprints in the Optical and Transport Properties of Quantum Dots. is the full-width-at-half-maximum (FWHM) of the autocorrelation function, , and   is the FWHM of the power spectrum. Fingerprints in the Optical and Transport Properties of Quantum Dots. separation of the peak Fingerprints in the Optical and Transport Properties of Quantum Dots 10 wavelengths resulting from a dot -in- well (DWELL) of different compositions is equal to the linewidth