Handbook of LUMINESCENT SEMICONDUCTOR MATERIALS Edited by Leah Bergman Jeanne L. McHale K11562 ISBN: 978-1-4398-3467-1 9 781439 834671 9 0 00 0 Handbook of Luminescent Semiconductor Materials Bergman McHale Materials Science Photoluminescence spectroscopy is an important approach for examining the optical interactions in semiconductors and optical devices with the goal of gaining insight into material properties. With contributions from researchers at the forefront of this field, Handbook of Luminescent Semiconductor Materials explores the use of this technique to study semiconductor materials in a vari- ety of applications, including solid-state lighting, solar energy conversion, optical devices, and biological imaging. After introducing basic semiconductor theory and photoluminescence principles, the book focuses on the optical properties of wide-bandgap semiconductors, such as AlN, GaN, and ZnO. It then presents research on narrow-bandgap semiconductors and solid-state lighting. The book also covers the optical properties of semiconductors in the nanoscale regime, including quantum dots and nanocrystals. Features • Provides a detailed examination of the photoluminescence properties of semiconductors, along with applications to semiconductor-based devices • Offers a condensed introduction to semiconductor photoluminescence that is ideal for nonexperts • Covers the photoluminescence and applications of nanoparticles • Presents a clear treatment of the role of impurities and defects in specific systems • Explores the application of narrow-bandgap and wide-bandgap semiconductors in devices, such as light-emitting diodes, lasers, and infrared detectors This handbook explains how photoluminescence spectroscopy is a powerful and practical analytical tool for revealing the fundamentals of light interaction and, thus, the optical properties of semiconductors. The book shows how luminescent semiconductors are used in lasers, photodiodes, infrared detectors, light-emitting diodes, solid-state lamps, solar energy, and biological imaging. Handbook of LUMINESCENT SEMICONDUCTOR MATERIALS Handbook of LUMINESCENT SEMICONDUCTOR MATERIALS Edited by Leah Bergman Jeanne L. McHale CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2012 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20110719 International Standard Book Number-13: 978-1-4398-3480-0 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the valid- ity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or uti- lized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopy- ing, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http:// www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com vii Contents Preface vii Editors ix Contributors xi 1 Principles of Photoluminescence 1 Baldassare Di Bartolo and John Collins 2 AlN: Properties and Applications 21 Ashok Sedhain, Jingyu Lin, and Hongxing Jiang 3 GaN-Based Optical Devices 69 Hiroaki Ohta, Steven P. DenBaars, and Shuji Nakamura 4 Photoluminescence of ZnO: Basics and Applications 87 Klaus onke and Martin Feneberg 5 Novel Applications of ZnO: Random Lasing and UV Photonic Light Sources 125 Hui Cao and Robert P.H. Chang 6 Luminescent ZnO and MgZnO 145 Leah Bergman, Jesse Huso, John L. Morrison, and M. Grant Norton 7 Luminescence Studies of Impurities and Defects in III-Nitride Semiconductors 169 Bo Monemar and Plamen P. Paskov 8 Narrow-Gap Semiconductors for Infrared Detectors 191 Antoni Rogalski 9 Solid-State Lighting 255 Lekhnath Bhusal and Angelo Mascarenhas 10 Fundamentals of the Quantum Confinement Effect 279 Patanjali Kambhampati 11 Selenide and Sulfide Quantum Dots and Nanocrystals: Optical Properties 307 Andrea M. Munro viii Contents 12 Radiative Cascades in Semiconductor Quantum Dots 321 Eilon Poem and David Gershoni 13 Photoluminescence and Carrier Transport in Nanocrystalline TiO 2 365 Jeanne L. McHale and Fritz J. Knorr 14 Photoluminescence Spectroscopy of Single Semiconductor Nanoparticles 391 Takashi Tachikawa and Tetsuro Majima 15 Biological Applications of Photoluminescent Semiconductor Quantum Dots 411 Oleg Kovtun and Sandra J. Rosenthal ix Preface In broad terms, photoluminescence is the science of light. e term luminescence means light emission, and photoluminescence is luminescence that is excited by a photon source. Photoluminescence spec- troscopy is a versatile technique enabling the study of light dynamics in matter, and it is an important approach for exploring the optical interactions in semiconductors and optical devices with the goal of gaining insight into material properties. is book is intended as a detailed examination of photolumi- nescence properties of semiconductors with applications to semiconductor-based devices. Chapter 1 provides the reader with an overview of basic semiconductor theory. e chapter presents the formalisms of semiconductor aspects such as bandgap, doping, and p–n junctions; these concepts are the fundamentals that underlie light emission and photoluminescence. In addition, it gives an out- line of the radiative transition mechanisms in semiconductors. e following six chapters focus on the optical properties of wide-bandgap semiconductors that include AlN, GaN, and ZnO. e bandgaps of this family of materials are in the range of ∼ 3 eV–6.2 eV, which is well into the UV spectral range. In particular, Chapter 2 addresses the electronic band structure and radiative recombination of AlN, as well as doping issues and application to devices. e topic of GaN and GaN-based optical devices is pre- sented in Chapter 3. at chapter describes the fundamentals of GaN-based blue light-emitting diodes and lasers. Chapter 4 provides a comprehensive overview of near-UV and visible photoluminescence of ZnO. Chapter 5 considers the applications of ZnO photoluminescence, including random lasing. e topic of optical alloys is presented in Chapter 6, where the issue of bandgap-engineered Mg x Zn 1−x O is addressed. Chapter 7 covers luminescence studies of impurities and defects in GaN, AlN, and InN. In particular, that chapter focuses on donors, acceptors, intrinsic point defects, and structural defects of the III-Nitride group. Chapters 8 and 9 present research on the topics of narrow-bandgap semiconductors and solid-state lighting, respectively. Chapter 8 gives a comprehensive description of the optical and electronic prop- erties of narrow-bandgap semiconductors and their application to infrared (IR) detectors. Among the narrow-bandgap materials discussed are the HgCdTe ternary alloys, InAsSb, PbS, PbSe, and InGaAs. It covers the properties of various optical devices such as photodiodes and IR detectors, as well as their manyfold applications to defense technologies as well as IR astronomy. Solid-state lighting involves materials in the visible spectrum, and is the topic of Chapter 9. e chapter covers the material and optical characteristics of low- and high-brightness light-emitting diodes and solid-state lamps. e fun- damentals of photometry, which is the science of luminosity, and colorimetry, which is the science of measurement of color, are discussed in detail. e next six chapters (Chapters 10 through 15) focus on the optical properties of semiconductors in the nanoscale regime. Chapter 10 covers the fundamental aspects of quantum eects unique to nanoparticles. Chapter 11 discusses the consequences of quantum connement in selenide and sulde quantum dots and nanocrystals. Chapter 12 presents the formalism and experiments of radiative cas- cade in semiconductor quantum dots. Chapter 13 considers the photoluminescence of nanocrystalline TiO 2 and its relation to the carrier transport properties that are important in solar energy applications. x Preface Chapter 14 continues the discussion of TiO 2 and other semiconductor nanoparticles, as revealed by the spectroscopy of individual nanoparticles. Finally, Chapter 15 reveals how the photoluminescence of semiconductor nanoparticles is proving useful in biological imaging applications. is handbook demonstrates that photoluminescence is a powerful and practical analytical tool for the study of the optical properties of semiconductors. e knowledge gained through photolumines- cence spectroscopy encompasses both the fundamentals of light interaction as well as valuable techno- logical applications. Leah Bergman Jeanne L. McHale xi Editors Leah Bergman is an associate professor of physics at the University of Idaho, Moscow, Idaho. She received her PhD in materials science and engineering in 1995 from North Carolina State University, Raleigh, North Carolina. She is a recipient of a CAREER award from the National Science Foundation division of DMR and was a postdoctoral fellow for the National Research Council. Dr. Bergman’s research is in the eld of optical materials with a focus on wide-bandgap luminescent semiconductors. Jeanne L. McHale is a professor of chemistry and materials science at Washington State University, Pullman, Washington. She received her PhD in physical chemistry in 1979 from the University of Utah, Salt Lake City, Utah. She is the author of Molecular Spectroscopy and a fellow in the American Association for the Advancement of Science. Dr. McHale’s research focuses on spectroscopic studies of semiconductor nanoparticles and chromophore aggregates relevant to solar energy conversion. [...]... Department University of California Santa Barbara, California Baldassare Di Bartolo Department of Physics Boston College Chestnut Hill, Massachusetts Martin Feneberg Institute for Experimental Physics University of Magdeburg Magdeburg, Germany David Gershoni Department of Physics The Technion—Israel Institute of Technology Haifa, Israel Jesse Huso Department of Physics University of Idaho Moscow, Idaho... atom devoid of any external influence will emit a photon and return to its ground state The spontaneity of the emission presents a conceptual problem A tenet of physical science, expressed by the so-called fluctuation-dissipation theorem sets forth the fact that any dissipation of energy from a system is the effect of its interaction with some external entity that provides 1 2 Handbook of Luminescent... the energy of the most energetic quantum state occupied at T = 0 At T ≠ 0, EF is the energy of a quantum state that has the probability 0.5 of being occupied The number of available states in (E, E + dE) for a system of electrons is given by Equation 1.4 The Fermi energy at T = 0 is determined by EF N= ∫ 0 = 8 2 πm3/2 2 g (E)dE = V h3 16 2 πm3/2 VEF 3/2 3h3 EF ∫E 1/ 2 dE 0 (1.6) 6 Handbook of Luminescent... correspondence to a value of the linear momentum equal → to zero or at the same k ≠ 0 Such semiconductors are called direct gap semiconductors In other materials, the maximum of the valence band and the minimum of the conduction band → occur at different values of k Such materials are called indirect gap semiconductors 12 Handbook of Luminescent Semiconductor Materials TABLE 1.3 List of Typical Semiconductors... made of group IV atoms, such as Si or Ge, is doped with group III atoms, such as Ga or Al, a hole for each of these atoms forms and remains loosely bound to the parent atom The amount of energy necessary to move an electron from the top of the valence band to one of these holes is labeled EA and is typically around 0.03 eV EA may also be called the ionization energy of the acceptor Both types of impurities... range of energy Process D The radiative decay of the exciton can be observed at a low temperature in very pure crystals There are two types of decay: 1 The decay of the free exciton 2 The decay of an exciton bound to an impurity Transitions of the first type are observed at low temperatures Since the exciton levels are well defined, a sharply structured emission can be expected As for the transitions of. .. of the transition is then ω(r ) = E g − E A − ED + e2 4πεokr (1.28) An example of such a transition is given by GaP containing sulfur donors and silicon acceptors, both set in phosphorous sites 1.13 Nonradiative Processes In the great majority of cases, a recombination of electrons and holes takes place by the emission of phonons Since the probability of such processes decreases with the number of. .. has been formed mechanically by pushing toward each other a bar of n-type semiconductor and a bar of p-type semiconductor, a junction plane divides the two regions (see Figure 1.6) Let us now examine the motion of the electrons (majority carriers of the n-type bar) and of holes (majority carriers of the p-type bar) Electrons on the n-side of the junction plane tend to diffuse (from right to left in the... The energy of the band gap of a semiconductor determines the spectral region in which the electronic transitions, both in absorption and emissions, take place For visible or near-infrared transitions, we need materials with gaps of ~1–1.7 eV A list of such materials is provided in Table 1.3 Direct gap transitions take place when the maximum energy of the valence band and the minimum energy of the conduction... the quantum states of the entire solid 3 Principles of Photoluminescence The most important classes of localized luminescent centers are Transition Metal Ions and Rare Earth Ions that are generally intentionally doped into ionic insulating host materials The luminescence properties of these systems depend on both the dopant ion and the host Another class of localized centers is that of defects in solids . with the goal of gaining insight into material properties. With contributions from researchers at the forefront of this field, Handbook of Luminescent. applications of nanoparticles • Presents a clear treatment of the role of impurities and defects in specific systems • Explores the application of narrow-bandgap