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Author : Weidong Yang
Publisher :
ISBN 13 :
Total Pages : 312 pages
Book Rating : 4.:/5 (449 download)
Download or read book Electronic Structure and Optical Properties of Self-assembled InAs Quantum Dots written by Weidong Yang and published by . This book was released on 1999 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Gik Hong Yeap
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (757 download)
Download or read book Electronic Structure and Optical Properties of Sb-based Self-assembled Quantum Dots for the Mid-infrared Range written by Gik Hong Yeap and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum dots (QDs) are zero-dimensional nanostructures that confined carriers in three dimensions comparable to their de Broglie wavelengths. Therefore, carriers exhibit?-shaped energy levels and densities of states. Due to their band structure, QD systems show significant advantages as active regions in laser cavities, both in term of lower threshold current densities and better thermal behaviour. The most studied system being InAs/GaAs system but the antimonide-based (Sb-based) material system has been paid much attention due to their potential for optical devices in the 3-5?m (0.25-0.40 eV) spectral regions and motivated by feasibility of active medium in high speed electronic and long wavelength photonic devices. In most cases, QDs structures had been obtained with an intrinsic elastic strain field arising from the lattice mismatch between the matrix and QD materials. The strain field plays a very significant role in the fabrication of the self-assembled QDs (SAQDs). Strain fields inside SAQD structures strongly affect the electronic band structure, which in turn, strongly affects the performance of optoelectronic devices. Therefore, knowledge and determination of the strain field in the dots and surrounding matrix is crucial in order to obtain a well ordered SAQDs structure. While knowledge and determination of the electronic structure calculation are necessary for further device modelling to improve the performance of the devices. Numerical work based on continuum-elasticity based on Finite Element Method (FEM) and standard-deformation-potential theory has been carried out to investigate the effect of strain on the band structure for InSb-based SAQD systems with type-I and type-II band alignment. The effect of elastic anisotropy on both strain distribution and band edges profile is also performed. Next, multi-band k?p method is used to model the electronic structure of InSb-based SAQD systems. The results from the modelling show that the strain-modified band profile of the zinc-blende III-V compound semiconductor SAQDs is not very sensitive to the details of the dot shape and the major governing parameter of the geometry is the aspect ratio of the dot. The modelling results also reveal that there are no appropriate material combinations for zinc-blende III-V compound semiconductors that would applicable for the MIR 3-5?m (0.25-0.40 eV) emission range when type-I band alignment is possible. This leads to the investigation of type-II broken gap InAsxSb(1-x)/InAs SAQDs. Finally, the optical properties of the InSb-based SAQDs are investigated by means of the photoluminescence (PL) measurement using Fourier transform infrared (FT-IR) spectroscopy. The PL results are analysed and compared to the modelling results.
Author : Tuan Anh Nguyen
Publisher :
ISBN 13 :
Total Pages : 218 pages
Book Rating : 4.:/5 (78 download)
Download or read book Investigations of Electronic Structure and Optical Properties of Ii-Vi Self-assembled Quantum Dots written by Tuan Anh Nguyen and published by . This book was released on 2006 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we use different optical and imaging spectroscopy techniques to study electronic structure and optical properties of CdTe/ZnTe and CdSe/ZnSe self-assembled quantum dots (SAQDs). We perform single dot photoluminescence excitation experiments to identify carrier excitation mechanisms in CdTe/ZnTe QDs. The first mechanism is direct excitation into the QD excited states followed by relaxation to the ground state and the second mechanism is direct excitation into the QD ground states through LO phonon-assisted absorption. We then execute resonant PL measurements for both CdTe and CdSe QD ensembles to study the dependence of exciton-LO phonon coupling on QD size in these II-VI SAQDs. We shown that the strength of exciton-LO phonon coupling increases significantly for QDs with lateral sizes smaller than the exciton Bohr radius (e.g. as-grown CdTe QDs) while for larger QDs (e.g. CdSe or CdTe annealed) it is almost independent of the QD emission energy, and therefore presumably of the QD size. In order to study electronic coupling between SAQDs, we setup imaging experiments with the use of a hemisphere solid immersion lens. While the PLE imaging measurements show the existence two-dimensional platelets with a typical size of about 500 nm which provide spatially extended but strong localized states through which different QDs could be populated simultaneously, the spatially resolved imaging data demonstrates a complete 2D map of those platelets. These results are further supported by computational calculations based on finite element analysis. Low temperature exciton spin relaxation in symmetric CdTe SAQDs has been thoroughly studied by means of cw polarized magneto-PL and polarized time-resolved PL spectroscopies. We find that the degeneracy of exciton energy levels has a strong influence on the spin transition. When the exciton spin states in QDs are degenerate, the spin relaxation time is much shorter than the exciton recombination time. In contrast, if this degeneracy is removed, either by asymmetry or an external magnetic field, the spin relaxation time becomes much longer than the exciton recombination time. Using simple rate equation models, we estimate exciton spin relaxation times equal to 4.8 ns and 50 ps for non-degenerate and degenerate QD states, respectively.
Author : Hao Lee
Publisher :
ISBN 13 :
Total Pages : 208 pages
Book Rating : 4.:/5 (422 download)
Download or read book Self-assembled InAs Quantum Dots written by Hao Lee and published by . This book was released on 1998 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Dieter Bimberg
Publisher : John Wiley & Sons
ISBN 13 : 9780471973881
Total Pages : 350 pages
Book Rating : 4.9/5 (738 download)
Download or read book Quantum Dot Heterostructures written by Dieter Bimberg and published by John Wiley & Sons. This book was released on 1999-03-17 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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)
Author : Zhiming M Wang
Publisher : Springer Science & Business Media
ISBN 13 : 0387741917
Total Pages : 470 pages
Book Rating : 4.3/5 (877 download)
Download or read book Self-Assembled Quantum Dots written by Zhiming M Wang and published by Springer Science & Business Media. This book was released on 2007-11-29 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Author : Michael Shur
Publisher : World Scientific
ISBN 13 : 9810249187
Total Pages : 214 pages
Book Rating : 4.8/5 (12 download)
Download or read book Quantum Dots written by Michael Shur and published by World Scientific. This book was released on 2002 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, leading experts on quantum dot theory and technology provide comprehensive reviews of all aspects of quantum dot systems. The following topics are covered: (1) energy states in quantum dots, including the effects of strain and many-body effects; (2) self-assembly and self-ordering of quantum dots in semiconductor systems; (3) growth, structures, and optical properties of III-nitride quantum dots; (4) quantum dot lasers.
Author : Saumya Sengupta
Publisher : Springer
ISBN 13 : 9811057028
Total Pages : 77 pages
Book Rating : 4.8/5 (11 download)
Download or read book Structural, Optical and Spectral Behaviour of InAs-based Quantum Dot Heterostructures written by Saumya Sengupta and published by Springer. This book was released on 2017-08-04 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores the effects of growth pause or ripening time on the properties of quantum dots(QDs). It covers the effects of post-growth rapid thermal annealing (RTA) treatment on properties of single layer QDs. The effects of post-growth rapid thermal annealing (RTA) treatment on properties of single layer QDs are discussed. The book offers insight into InAs/GaAs bilayer QD heterostructures with very thin spacer layers and discusses minimum spacer thickness required to grow electronically coupled bilayer QD heterostructures. These techniques make bilayer QD heterostructures a better choice over the single layer and uncoupled multilayer QD heterostructure. Finally, the book discusses sub-monolayer (SML) growth technique to grow QDs. This recent technique has been proven to improve the device performance significantly. The contents of this monograph will prove useful to researchers and professionals alike.
Author : Zhifeng Wei
Publisher : Open Dissertation Press
ISBN 13 : 9781374667532
Total Pages : pages
Book Rating : 4.6/5 (675 download)
Download or read book The Optical Response of Semiconductor Self-Assembled Quantum Dots written by Zhifeng Wei and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "The Optical Response of Semiconductor Self-assembled Quantum Dots" by Zhifeng, Wei, 魏志鋒, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled THE OPTICAL RESPONSE OF SEMICONDUCTOR SELF-ASSEMBLED QUANTUM DOTS Submitted by Wei Zhifeng for the degree of Doctor of Philosophy at The University of Hong Kong in May 2006 Self-assembled quantum dots (QDs) are one type of tiny coherent islands which spontaneously form via the Stranski-Krastanow (S-K) growth mode during the heteroepitaxial growth of lattice-mismatched thin films. They have attracted considerable interest in recent years because of their atom-like properties and many potential applications in novel electronic and photonic devices. A detailed investigation on the optical properties of semiconductor QDs was presented in this thesis project. The variable-temperature photoluminescence (PL) spectra of two kinds of InGaAs QDs with and without a GaAs cap layer were comparatively investigated. It was found that the optical properties of the buried QDs with the cap layer differ significantly from those of the surface QDs. The growth of cap layer can improve the dots uniformity indicated by the narrow PL peak, greatly enhance the luminescence efficiency, and result in a large blueshift of the emission peak due to the strain environment change of the QDs. The cap layer also improves the thermal stability of the QD emission. The spontaneous emission mechanisms of two quaternary self-assembled GaInAsN QDs with different compositions and growth thicknesses have been studied. Adopting a newly developed localized-states luminescence model, the temperature behavior of the emissions from the two GaInAsN QDs has been quantitatively interpreted. The physical pictures of the spontaneous emissions of GaInAsN QDs were established. For the self-assembled QDs, a strained thin layer underneath the QDs always exists and this two-dimensional thin layer is called the wetting layer (WL). A quantitative study on the role of WL in the luminescence process of InAs/GaAs self- assembled QDs has been conducted. It has been shown that the WL acts as an efficient bridge not only in the relaxation of carriers from the barrier layer to the QDs but also in the thermal escaping of the carriers already captured by the QDs. Since the knowledge of electronic structure and optical transitions of self- assembled QDs is essentially important for the infrared detection applications of the QDs, a precise PL spectroscopic probe of the electronic structures of InAs/GaAs QDs with various silicon doping concentrations has been carried out. The theoretical predicted blueshift of the fundamental transitions of the QDs has been observed as the Si doping concentration and thus the number of electrons loaded into the dot is increased. It was also found that the Si δ-doping at the central regions of barrier layers during the growth of multi-layered QDs can significantly improve the luminescence efficiency of the samples at higher temperatures. Growth and optical characterizations of the electrically coupled InAs and InP QD stacking structures have been done. The study provides a possible way to produce a new type of broad-band QD light emitting diodes via the so-called band-engineering method. DOI: 10.5353/th_b3709820 Subjects: Quantum dots Semiconductors - Optical properties
Author :
Publisher : Academic Press
ISBN 13 : 0080864589
Total Pages : 385 pages
Book Rating : 4.0/5 (88 download)
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.
Author : Bruce A. Joyce
Publisher : Springer Science & Business Media
ISBN 13 : 140203315X
Total Pages : 401 pages
Book Rating : 4.4/5 (2 download)
Download or read book Quantum Dots: Fundamentals, Applications, and Frontiers written by Bruce A. Joyce and published by Springer Science & Business Media. This book was released on 2006-03-30 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains papers delivered at a NATO Advanced Research Workshop and provides a broad introduction to all major aspects of quantum dot structures. Such structures have been produced for studies of basic physical phenomena, for device fabrication and, on a more speculative level, have been suggested as components of a solid-state realization of a quantum computer. The book is structured so that the reader is introduced to the methods used to produce and control quantum dots, followed by discussions of their structural, electronic, and optical properties. It concludes with examples of how their optical properties can be used in practical devices, including lasers and light-emitting diodes operating at the commercially important wavelengths of 1.3 Am and 1.55 Am."
Author : Elena Borovitskaya
Publisher : World Scientific
ISBN 13 : 9814488798
Total Pages : 214 pages
Book Rating : 4.8/5 (144 download)
Download or read book Quantum Dots written by Elena Borovitskaya and published by World Scientific. This book was released on 2002-07-08 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, leading experts on quantum dot theory and technology provide comprehensive reviews of all aspects of quantum dot systems. The following topics are covered: (1) energy states in quantum dots, including the effects of strain and many-body effects; (2) self-assembly and self-ordering of quantum dots in semiconductor systems; (3) growth, structures, and optical properties of III-nitride quantum dots; (4) quantum dot lasers.
Author : Mohamed Henini
Publisher : Elsevier
ISBN 13 : 0080560474
Total Pages : 862 pages
Book Rating : 4.0/5 (85 download)
Download or read book Handbook of Self Assembled Semiconductor Nanostructures for Novel Devices in Photonics and Electronics written by Mohamed Henini and published by Elsevier. This book was released on 2011-07-28 with total page 862 pages. Available in PDF, EPUB and Kindle. Book excerpt: The self-assembled nanostructured materials described in this book offer a number of advantages over conventional material technologies in a wide range of sectors. World leaders in the field of self-organisation of nanostructures review the current status of research and development in the field, and give an account of the formation, properties, and self-organisation of semiconductor nanostructures. Chapters on structural, electronic and optical properties, and devices based on self-organised nanostructures are also included. Future research work on self-assembled nanostructures will connect diverse areas of material science, physics, chemistry, electronics and optoelectronics. This book will provide an excellent starting point for workers entering the field and a useful reference to the nanostructured materials research community. It will be useful to any scientist who is involved in nanotechnology and those wishing to gain a view of what is possible with modern fabrication technology. Mohamed Henini is a Professor of Applied Physics at the University of Nottingham. He has authored and co-authored over 750 papers in international journals and conference proceedings and is the founder of two international conferences. He is the Editor-in-Chief of Microelectronics Journal and has edited three previous Elsevier books. Contributors are world leaders in the field Brings together all the factors which are essential in self-organisation of quantum nanostructures Reviews the current status of research and development in self-organised nanostructured materials Provides a ready source of information on a wide range of topics Useful to any scientist who is involved in nanotechnology Excellent starting point for workers entering the field Serves as an excellent reference manual
Author : Yasuaki Masumoto
Publisher : Springer Science & Business Media
ISBN 13 : 9783540428053
Total Pages : 520 pages
Book Rating : 4.4/5 (28 download)
Download or read book Semiconductor Quantum Dots written by Yasuaki Masumoto and published by Springer Science & Business Media. This book was released on 2002-05-28 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 ...
Author : Ameenah Al-Ahmadi
Publisher : BoD – Books on Demand
ISBN 13 : 9535106481
Total Pages : 482 pages
Book Rating : 4.5/5 (351 download)
Download or read book Fingerprints in the Optical and Transport Properties of Quantum Dots written by Ameenah Al-Ahmadi and published by BoD – Books on Demand. This book was released on 2012-06-13 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book "Fingerprints in the optical and transport properties of quantum dots" provides novel and efficient methods for the calculation and investigating of the optical and transport properties of quantum dot systems. This book is divided into two sections. In section 1 includes ten chapters where novel optical properties are discussed. In section 2 involve eight chapters that investigate and model the most important effects of transport and electronics properties of quantum dot systems This is a collaborative book sharing and providing fundamental research such as the one conducted in Physics, Chemistry, Material Science, 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.
Download or read book Optical properties of self-assembled In(Ga)As quantum dots written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Optical Study of the Electronic Structure of CdSe/ZnSe and CdTe/ZnTe Self Assembled Quantum Dots written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the excitonic structure and optical properties of single quantum dots in three different II-VI semiconductor structure systems: as-grown CdSe/ZnSe, as-grown CdTe/ZnTe, and annealed CdTe/ZnTe self-assembled quantum dots(QD) using photoluminescence(PL), micro-PL, micro-PL obtained using a sub-wavelength aperture, and PL images obtained using a Solid Immersion Lens (SIL). These experiments are performed both at zero field and magnetic field up to 3 Tesla. While in zero field, linear polarized PL are used to find exchange splitting and QD asymmetry direction of the three QD samples, in a 3 Tesla magnetic field, circular polarized PL is used to determine the g-factor and diamagnetic shift. With a solid immersion lens (SIL), we are able to directly image a large number of single QD at 6K with 400 nm spatial resolution. Using zero field measurements, we find that while the some of the QDs are symmetric, and emit completely unpolarized light, over half of the QDs are antisymmetric which are typically aligned along one of the in-plane crystallographic directions, and so emit linear polarized PL. Since polarization properties as well as spin properties such as exchange splitting, g-factor and diamagnetic coefficient are different from dot to dot due to their size and asymmetry variations, we have carried out a statistical study of these properties in order to understand what changes occur in the QDs between these three samples. The major result from this work shows that thermal annealing of CdTe dots significantly reduces the statistical variation of exchange splittings for asymmetric dots as well as the g-factors for symmetric dots. We infer that these changes result from enlargement of the CdTe dots due to interdiffusion of Zn between the barriers and the dots. This enlargement is reflected in the increase of the median distributions of the diamagnetic shifts. Moreover, in CdSe dots, where the dot size is comparable or slightly larger than the exciton Bohr diameter, we find that the variation of these parameters is reduced as well.
