Dynamics of Excitons in GaAs-AlxGa1-xAs Multiple Quantum Wells Probed by Time-resolved Photoluminescence PDF Download
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Author: Er-Xuan Ping
Publisher:
ISBN:
Category :
Languages : en
Pages : 102
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Author: Er-Xuan Ping
Publisher:
ISBN:
Category :
Languages : en
Pages : 102
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Author: M. Zachau
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ISBN:
Category :
Languages : en
Pages : 4
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We measure the time dependence of the excitonic photoluminescence (PL) in quantum wells (QWs) with well width Lz ranging from 25A to 50A. The samples are AI0.2Ga0.8As/GaAs multiple QWs with 30 periods with decoupled wells and were grown by molecular beam epitaxy (MBE). QWs grown with and without growth interruption at the interfaces are investigated. The excitation is provided by 5 psec pulses from a synchronously pumped tunable dye laser. The PL spectrum is detected by an imaging (i.e. multichannel) photomultiplier with a spectral resolution of 0.5 meV and time resolution (FWHM) of 120 psec.
Author: Howard Wuk Yoon
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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: Linda Jean Blue
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Category : Quantum wells
Languages : en
Pages : 282
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Author: Mary-Ann Mycek
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Category :
Languages : en
Pages : 368
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Author: Yasuaki Masumoto
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Category :
Languages : en
Pages : 16
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Category : Chemistry
Languages : en
Pages : 2002
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Author: J. B. Stark
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Category :
Languages : en
Pages : 4
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Spatial confinement along one dimension, using the methods of epitaxial crystal growth, has demonstrated that linear and nonlinear optical properties depend strongly on dimensionality. Confinement along the remaining directions, however, continues to present formidable technological obstacles. Difficulties in the control of the surface properties and size distribution of quantum dots and semiconductor microcrystallites results in materials with unsatisfactory optical quality. Confinement along all three dimensions can be achieved, in materials of excellent optical quality, by placing a quantum well material in a perpendicular magnetic field. As the field is increased, the extension of the resulting electronic orbitals decreases, so that the dimensionality of the states may be tuned from two to zero dimensions. Using femtosecond excite-and-probe optical techniques in fields as large as 12 Tesla, we measure the time resolved dynamics of zero dimensional magneto-excitons.
![Electrical Control of the Electron Spin Dynamics in [111]-oriented GaAs/AGaAs Quantum Wells PDF](https://books.google.com/books/content/images/frontcover/8ix1ngEACAAJ?fife=w80-h100)
Author: Quang ha Duong
Publisher:
ISBN:
Category :
Languages : en
Pages : 125
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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.
Author: Sabine Zybell
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Category :
Languages : en
Pages :
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