Optical and Transport Properties of Excitons in Single and Coupled Quantum Wells PDF Download

Author: Smadar Ben-Tabou de-Leon
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 244

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Author: Jason Leonard
Publisher: Springer
ISBN: 9783319888347
Category : Technology & Engineering
Languages : en
Pages : 59

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This thesis presents results crucial to the emerging field of indirect excitons. These specially designed quasiparticles give the unique opportunity to study fundamental properties of quantum degenerate Bose gases in semiconductors. Furthermore, indirect excitons allow for the creation of novel optoelectronic devices where excitons are used in place of electrons. Excitonic devices are explored for the development of advanced signal processing seamlessly coupled with optical communication. The thesis presents and describes the author's imaging experiments that led to the discovery of spin transport of excitons. The many firsts presented herein include the first studies of an excitonic conveyer, leading to the discovery of the dynamical localization-delocalization transition for excitons, and the first excitonic ramp and excitonic diode with no energy-dissipating voltage gradient.

Author: Yuliya Yevgenyevna Kuznetsova
Publisher:
ISBN: 9781321451900
Category :
Languages : en
Pages : 67

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This dissertation explores studies of transport of indirect excitons (bosonic quasiparticles composed of bound pairs of an electron and a hole confined to spatially separated layers) in GaAs coupled quantum wells. The small mass and long lifetime of indirect excitons result in a relatively high quantum degeneracy temperature and efficient cooling, making indirect excitons a model system for studies of physics of cold bosons. In addition, indirect excitons are optically active, electronically controllable and have long enough lifetimes that their transport distances can be accommodated by lithography. These properties make indirect excitons a promising system for creating excitonic devices. The direction of the research presented in this dissertation is thus twofold: studying fundamental physics of excitons, including transport, thermalization, coherence, spin currents, and properties in high magnetic fields, and realization of optical excitonic devices, such as traps and transistors.

Author: Jason Leonard
Publisher: Springer
ISBN: 3319697331
Category : Technology & Engineering
Languages : en
Pages : 67

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Book Description
This thesis presents results crucial to the emerging field of indirect excitons. These specially designed quasiparticles give the unique opportunity to study fundamental properties of quantum degenerate Bose gases in semiconductors. Furthermore, indirect excitons allow for the creation of novel optoelectronic devices where excitons are used in place of electrons. Excitonic devices are explored for the development of advanced signal processing seamlessly coupled with optical communication. The thesis presents and describes the author's imaging experiments that led to the discovery of spin transport of excitons. The many firsts presented herein include the first studies of an excitonic conveyer, leading to the discovery of the dynamical localization-delocalization transition for excitons, and the first excitonic ramp and excitonic diode with no energy-dissipating voltage gradient.

Author: Ameenah Al-Ahmadi
Publisher: BoD – Books on Demand
ISBN: 9535106481
Category : Science
Languages : en
Pages : 482

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Book Description
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.

Author: Paul Harrison
Publisher: John Wiley & Sons
ISBN: 0470010819
Category : Science
Languages : en
Pages : 511

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Book Description
Quantum Wells, Wires and Dots Second Edition: Theoretical andComputational Physics of Semiconductor Nanostructures providesall the essential information, both theoretical and computational,for complete beginners to develop an understanding of how theelectronic, optical and transport properties of quantum wells,wires and dots are calculated. Readers are lead through a series ofsimple theoretical and computational examples giving solidfoundations from which they will gain the confidence to initiatetheoretical investigations or explanations of their own. Emphasis on combining the analysis and interpretation ofexperimental data with the development of theoretical ideas Complementary to the more standard texts Aimed at the physics community at large, rather than just thelow-dimensional semiconductor expert The text present solutions for a large number of realsituations Presented in a lucid style with easy to follow steps related toaccompanying illustrative examples

Author: Jason R. Leonard
Publisher:
ISBN:
Category :
Languages : en
Pages : 83

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Book Description
In GaAs excitons are optically active making them ideally suitable for optical communications and computation. An exciton is composite particle composed of an electron and hole. Indirect excitons are excitons with the electron and hole spatially separated into different quantum wells. Indirect excitons are oriented in the same direction allowing indirect excitons to be manipulated by voltage gradients. This dissertation explores controlling exciton transport with ramps--shaped electrodes that operate as excitonic diodes, or in a crossed ramp configuration operate as an optically controlled transistor. This dissertation also demonstrates an exciton conveyer--a moving lattice created by electrodes driven with AC voltages--that transports excitons over large distances. This dissertation concludes with an observation of exciton spin transport.

Author: Howard Wuk Yoon
Publisher:
ISBN:
Category :
Languages : en
Pages :

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This thesis describes the use of optical absorption and photoluminescence spectroscopy in understanding the spatial transport and energy relaxation of excitons in quantum well systems. I discuss the mechanism of carrier-induced changes in the absorption spectrum of a 210A GaAs multiple quantum well, and show that at moderate densities, the enhanced transmission at the heavy-hole exciton energy is due to collision broadening. I also discuss the time dependent and excitation-energy dependent energy shifts of the heavy-hole exciton. I use the changes induced in the absorption spectra due to the presence of carriers as a probe for measuring the spatial transport, and I describe the transport using an ionized-impurity scattering model. I also measure the carrier temperatures from the high energy slopes of the time-resolved photoluminescence spectra, and describe the roles of the carrier temperatures and carrier expansion on the time dynamics of the exciton luminescence intensity. In the last chapter, I study the transport properties of excitons in an asymmetric-coupled quantum well system, and explain the experimental results with a model based on interface-roughness scattering.

Author: Aaron Tynes Hammack
Publisher:
ISBN: 9781109764604
Category :
Languages : en
Pages : 168

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Book Description
The study of excitons in semiconductors is a rich field that has seen numerous beautiful developments during the seven decades since they were proposed by Frenkel [1931]. The exciton states in dielectric materials and molecular complexes are fundamental to understanding the full electronic structure of materials and the complex interactions between light and matter. Of particular interest is the fact that excitons, bound electron-hole pairs, form composite bosons with very low effective masses. This opens up an incredibly rich opportunity to study the phase space of quantum degenerate Bose gases at relatively high temperatures. An overview of many of the rich features that have been observed in exciton gases is presented. The system of indirect excitons in coupled quantum wells (CQWs) provides for drastically increased and tunable exciton lifetimes, leading to improved thermalization. The present experimental study presents a full steady state and dynamic model for the transport, generation, recombination, and thermalization of indirect excitons in CQWs, as well as methods for in-situ manipulation of indirect excitons by both optical and electrical methods. Both the optical and electrical methods for exciton control provide for dynamic manipulation of excitons on timescales significantly shorter than the lifetimes of indirect excitons.

Author: Joe Wilkes
Publisher:
ISBN:
Category :
Languages : en
Pages :

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This thesis comprises a theoretical study of the dynamics of indirect excitons in coupled quantum wells at low lattice temperatures. The results of numerical simulations of the exciton photoluminescence pattern are presented and compared to available experimental data. The in-plane transport of quantum well excitons created by laser excitation is modeled using a non-linear drift-diffusion equation. Combined with a model of exciton relaxation thermodynamics, a complete description of the evolution of the exciton density and temperature is built. The optical decay of indirect excitons is included in the modeling. This is used to make predictions of the spatial photoluminescence patterns which have been observed experimentally. The transport of dipole orientated excitons via externally applied electrostatic potentials is also studied. The drift-diffusion equation is adapted to include the inplane electric field. This is done for some specific forms of the potential landscapes such as a linear potential energy gradient and a propagating lattice. These correspond to some recent experiments for which results are available. The combined theoretical and experimental studies reveal a deeper insight into the transport properties of indirect excitons. Finally, the external ring structure in the indirect exciton emission pattern is studied. Its formation is modeled using a set of coupled transport equations for electrons, holes and indirect excitons. The Coulomb interactions between all three species are incorporated in the model. It is shown that these interactions lead to an instability in the external ring and are responsible for its fragmentation into a periodic array of islands which has been observed experimentally.