Optical properties of II-VI compound low -dimensional structures grown by molecular beam epitaxy.
Item
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Title
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Optical properties of II-VI compound low -dimensional structures grown by molecular beam epitaxy.
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Identifier
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AAI3170003
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identifier
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3170003
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Creator
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Zhou, Xuecong.
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Contributor
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Advisers: Maria C. Tamargo | Ying-Chih Chen
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter
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Abstract
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This thesis describes Molecular-Beam Epitaxy (MBE) growth and investigation of the optical properties of a series of materials and structures based on wide-band-gap II-VI materials that have potential applications as light emitting devices, in particular laser diodes. Three types of materials are presented in details: single layers of ZnxCdyMg1-x-ySe with different Mg concentrations, optically-pumped blue Znx' Cdy'Mg1-x-' y'Se/ZnxCdyMg 1-x-ySe single quantum well (QW) laser structures grown on InP, and CdSe self-assembled quantum dot (SAQD) structures grown on ZnSe, Zn1-x BexSe as well as ZnCdMgSe. The goal is to better understand the state of the art QW laser structures based on ZnCdMgSe and propose improvement by using lower-dimensional structures for these devices.;The optical properties of ZnxCdyMg1-x-y Se alloys using photoluminescence (PL) and photoluminescence excitation are systematically studied. It is shown that, at low temperatures, PL is dominated by excitons localized by potential fluctuations, which becomes stronger with increasing Mg concentration. Such potential fluctuations are discussed in terms of a large valence band offset in Zn(Cd)Se/MgSe systems, which serves as a manifestation of the breakdown of "Common-anion Rule".;The lasing operations of the photo-pumped Znx'Cd y'Mg1-x'-y 'Se/ZnxCdyMg1-x-y Se separate confinement heterostructure single QW blue and green lasers grown lattice matched to InP are reported. A lower threshold pumping intensity and higher characteristic temperature are obtained for the green laser, which is explained on the basis of the difference in carrier confinement between these two structures.;For the CdSe/ZnSe and CdSe/Zn0.97Be0.03Se SAQDs, the self-assembled growth is reported; the atomic force microscopy measurements on uncapped QDs are given; the steady-state PL and time-resolved PL are performed. Further the QD size and Cd composition are estimated and compared using two different methods for these two QD structures.;The effect of Be concentration on the formation of CdSe SAQDs grown on Zn1-xBexSe is investigated. Systematic decrease of the QD size by increasing the Be concentration in the Zn1-x BexSe barrier layer is demonstrated. Finally, exploring work for the growth of CdSe/ZnCdMgSe SAQDs is shown, and the initial results are given. By simply changing the deposition time of CdSe, emission through the whole visible range from blue to red has been obtained.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
