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Book Measurement of Electron hole Friction in an N doped GaAs AlGaAs Quantum Well Using Optical Transient grating Spectroscopy

Download or read book Measurement of Electron hole Friction in an N doped GaAs AlGaAs Quantum Well Using Optical Transient grating Spectroscopy written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We use phase-resolved transient grating spectroscopy to measure the drift and diffusion of electron-hole density waves in a semiconductor quantum well. The unique aspects of this optical probe allow us to determine the frictional force between a two-dimensional Fermi liquid of electrons and a dilute gas of holes. Knowledge of electron-hole friction enables prediction of ambipolar dynamics in high-mobility electron systems.

Book Electrons Phonons and Their Interactions in Novel Modulation Doped GaAs AlAs Based Quantum Wells

Download or read book Electrons Phonons and Their Interactions in Novel Modulation Doped GaAs AlAs Based Quantum Wells written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lowest energy interband transitions in AlGaAs/AlAs quantum wells involve electrons localized in the AlAs x-valleys and holes confined in the AlGaAs layers. These transitions are indirect in both real as well as in kappa-space and are accompanied by strong replicas of the GaAs and AlAs phonons. When a magnetic field is applied perpendicular to the layers a large reduction in the recombination intensity is observed. This reduction is attributed to magnetic field induced localization of the carriers which results in a reduction of the electron-hole wavefunction overlap. We have also studied photoluminescence spectra from type-II, n-type, modulation doped GaAs/AlAs quantum wells due to radiative recombination of electrons localized in the AlAs x-valleys with holes confined in the GaAs layers. In the presence of a magnetic field the emission spectra exhibit features associated with transitions among the AlAs x-valley Landau levels and photo-injected holes. The slopes of these transitions yield an effective mass m = 0.44 for the electrons.

Book Physics Briefs

Download or read book Physics Briefs written by and published by . This book was released on 1991 with total page 1328 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Electron Transmission Through Non Tunneling Regime of GAAS Algaas Coupled Quantum Wells

Download or read book Electron Transmission Through Non Tunneling Regime of GAAS Algaas Coupled Quantum Wells written by Sujaul Chowdhury and published by Grin Publishing. This book was released on 2017-10-02 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research Paper (postgraduate) from the year 2017 in the subject Physics - Quantum Physics, grade: 4.00, Shahjalal University of Science and Technology, course: Nanostructure Physics, language: English, abstract: We have investigated electron transmission through non-tunneling regime of a semiconductor nanostructure called Coupled Quantum Well (CQW). Oscillatory transmission coefficient as a function of energy is found to show spectacular waxing and waning in amplitude. Corresponding features are expected to be observed in optical (Physical Review B 54 (1996) 1541) and quantum transport (Physical Review Letters 58 (1987) 816) experiments and hence the results besides verifying the Physics will have impact on future devices based on CQW.

Book Spectroscopy of GaAs Quantum Wells

Download or read book Spectroscopy of GaAs Quantum Wells written by Lawrence Camest West and published by . This book was released on 1985 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Electrical Control of the Electron Spin Dynamics in 111 oriented GaAs AGaAs Quantum Wells

Download or read book Electrical Control of the Electron Spin Dynamics in 111 oriented GaAs AGaAs Quantum Wells written by Quang ha Duong and published by . This book was released on 2013 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have studied the electron spin dynamics in 111-oriented GaAs/AlGaAs quantum wells grown on 111-substrate by time-resolved photoluminescence spectroscopy. By applying an external electric field about 50 kV/cm along growth direction, we observed the spectacular increase of electron spin which can attain values greater than 30 ns. This phenomenon comes from the electrical control of spin-orbit interaction in conduction band that make the Rashba term compensate exactly with the Dresselhaus term. The cancellation effect of these two terms results in the suppression of electron spin relaxation induced by D'yakonov-Perelmechanism which is dominant in undoped quantum wells and at the temperatures greater than 50K. The measurement under an external transverse magnetic field (Voigt configuration) demonstrates that the spin relaxation times in three spatial directions are also controlled simultaneously by electric field. The "total" control of electron spin relaxation can only be observed in 111-oriented quantum wells. Finally, we also develop the model to interpret the experimental measurement of spin relaxation anisotropy depending on electric field in 111-oriented quantum wells.

Book Spectroscopy of Single Free Standing Quantum Wells

Download or read book Spectroscopy of Single Free Standing Quantum Wells written by M. D. Williams and published by . This book was released on 2006 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigated the interaction of quantum confined exciton states GaAs quantum wells with native surface states. Single molecule photoluminescence (PL) spectroscopy, developed by T. Huser at LLNL was used to probe the unique bare quantum wells in the free standing quantum well structure. The latter was developed by the M.D. Williams at Clark Atlanta University. The goals of the project during this budget cycle were to procure samples containing GaAs free standing QWs, identify suitable regions for PL analysis at Lawrence Livermore, analyze the structures at room temperature and at liquid nitrogen temperatures. The specific regions of interest on the sample structures were identified by scanning electron microscopy at Clark Atlanta prior to transport to LLNL. Previous attempts at other facilities using NSOM, cathodoluminescence, and conventional PL showed little luminescence activity at room temperature from the 200 {angstrom} thick wells. This suggested either excess recombination due to surface states in the quantum well region or insufficient absorption length for photoluminescence. The literature suggested that the effect of the defects could be eliminated by reducing the sample temperature below their associated activation energies. In our previous subcontract work with LLNL, a significant amount of effort was expended to modify the apparatus to allow low temperature measurements. The modifications were not successful and we concluded that in order to do the measurements at low temperature we would need to purchase a commercial optical cryostat to get reliable results. Ms. Rochelle Bryant worked during the summer as an intern at LLNL on the project under the supervision of C. Hollars and in collaboration with T. Huser and found that PL emission could be obtained at room temperature. This was a surprising result as the literature and our experience shows that there is no PL emission from GaAs at room temperature. We speculate that this is due to the small interaction region excited by the laser source. We proceeded with the project using this new found room temperature capability and have analyzed the effect of various chemical species on the PL emission from the GaAs QWs. We were able to observe some significant intensity modifications of the PL spectra with chemical adsorbants. This progress holds promise for the development of this structure as a chemical or biological sensor.

Book Tunnelling Spectroscopy in GaAs AlGaAs Double Quantum Well Devices

Download or read book Tunnelling Spectroscopy in GaAs AlGaAs Double Quantum Well Devices written by Neil Turner and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Breakdown of the Quantum Hall Effect in InGaAs InP Quantum Wells

Download or read book Breakdown of the Quantum Hall Effect in InGaAs InP Quantum Wells written by Victor Yu and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The quantum Hall effect occurs in a two-dimensional electron gas confined in a quantum well when subjected to a high perpendicular magnetic field. By passing a sufficiently high current through a Hall bar, the quantum Hall effect can be destroyed. A rich variety of non-linear phenomena can be accessed at and beyond current-induced quantum Hall breakdown. One example is hysteresis arising from dynamic nuclear polarization through the interplay of electron and nuclear spins via the hyperfine interaction. Another example is electric instability leading to resistance fluctuations and negative differential resistance. These phenomena are typically observed in widely studied GaAs/AlGaAs heterostructure quantum well Hall bar devices. We report on the characteristics of hysteresis and electric instability seen at and beyond quantum Hall breakdown in InGaAs/InP quantum well Hall bar devices. Such indium-based quantum wells are of current interest for spintronic applications. As compared to widely employed GaAs/AlGaAs quantum wells, InGaAs/InP quantum wells offer larger electron g-factors, stronger spin-orbit coupling, and the nuclear spin for indium (9/2) is larger than for gallium (3/2). We investigate non-linear magnetotransport in three long (200-300 um) and narrow (15 um) Hall bar devices made from a strained InGaAs/InP quantum well and can change the electron sheet density by careful illumination. Two-dimensional maps of voltage or resistance as a function of current and magnetic field are generated. These maps may be regarded as phase diagrams since they provide a wealth of information about the conditions for quantum Hall breakdown, hysteresis, electric instability, and a number of other phenomena. We document extensively how the quantum Hall breakdown and non-linear phenomena evolve systematically not only with increasing magnetic field but also with increasing electron sheet density. Regarding the hysteresis, we find that it is pronounced when spin-polarized quantum Hall states break down. The hysteresis is accompanied by slow change of measured signal on timescales of a few minutes or even a few hours. We examine whether the observed hysteresis and time dependent behaviour are consistent with a picture of dynamic nuclear polarization or if it has its origin elsewhere. Regarding the electric instability, it becomes prevalent at high current over a wide range of magnetic field at high electron sheet density when the differential resistance along the Hall bar device approaches zero or becomes negative. Our observations may provide insight into the formation of domains within the Hall bar that carry different currents, and turbulent electron flow." --

Book The Physics of Semiconductors

Download or read book The Physics of Semiconductors written by Marius Grundmann and published by Springer Nature. This book was released on 2021-03-06 with total page 905 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 4th edition of this highly successful textbook features copious material for a complete upper-level undergraduate or graduate course, guiding readers to the point where they can choose a specialized topic and begin supervised research. The textbook provides an integrated approach beginning from the essential principles of solid-state and semiconductor physics to their use in various classic and modern semiconductor devices for applications in electronics and photonics. The text highlights many practical aspects of semiconductors: alloys, strain, heterostructures, nanostructures, amorphous semiconductors, and noise, which are essential aspects of modern semiconductor research but often omitted in other textbooks. This textbook also covers advanced topics, such as Bragg mirrors, resonators, polarized and magnetic semiconductors, nanowires, quantum dots, multi-junction solar cells, thin film transistors, and transparent conductive oxides. The 4th edition includes many updates and chapters on 2D materials and aspects of topology. The text derives explicit formulas for many results to facilitate a better understanding of the topics. Having evolved from a highly regarded two-semester course on the topic, The Physics of Semiconductors requires little or no prior knowledge of solid-state physics. More than 2100 references guide the reader to historic and current literature including original papers, review articles and topical books, providing a go-to point of reference for experienced researchers as well.

Book Millimeter and Submillimeter Wave Spectroscopy of Solids

Download or read book Millimeter and Submillimeter Wave Spectroscopy of Solids written by George Grüner and published by Springer. This book was released on 2014-03-12 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: Millimeter and Submillimeter Wave Spectroscopy of Solids focuses on the experimental methods and recent experimental results which are currently employed in the millimeter wave spectral range. Time dome, Fourier transform, coherent source and resonant techniques are discussed by leading authorities in the field. The usefulness of the methods is discussed by reviewing experimental results on metals and semiconductors. Recent experiment covering modern topics such as correlation on metals, superconductors and confined quantum systems are also discussed. The volume is aimed at physicists, engineers and materials scientists interested in the dynamics of solid matter.

Book Laser Induced Dynamic Gratings

Download or read book Laser Induced Dynamic Gratings written by Hans Joachim Eichler and published by Springer. This book was released on 2013-06-29 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: The invention ofthe laser 25years ago resulted in powerfullight sources which led to the observation of unexpected and striking phenomena. New fields of science such as holography and nonlinear optics developed constituting the basis of this volume. The classical principle of linear superposition of light wavesdoes not hold anymore. Two laser beams crossing in a suitable material may produce a set of new beams with different directions and frequencies. The interaction of light waves can be understood by considering the optical grating structures which develop in the overlap region. The optical properties of matter become spatially modulated in the interference region of two light waves. Permanent holographic gratings have been produced in this way by photographic processes for many years. In contrast, dynamic or transient gratings disappear after the inducing light source, usually a laser, has been switched off. The grating amplitude is controlled by the light intensity. Dynamic gratings have been induced in a large number ofsolids, liquids, and gases, and are detected by diffraction, 'forced light scattering' of a third probing beam, or by self-diffraction of the light waves inducing the grating. The combined interference and diffraction effect corresponds to four-wave mixing (FWM) in the language of nonlinear optics. The process is called degenerate ifthe frequenciesofthe three incident wavesand the scattered wave are equal. Degenerate four-wave mixing (DFWM) is a simple method to achieve phase conjugation, i.e. to generate a wave which propagates time reversed with respect to an incident wave.