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991.
E. Kapon M. Walther J. Christen M. Grundmann C. Caneau D.M. Hwang E. Colas R. Bhat G.H. Song D. Bimberg 《Superlattices and Microstructures》1992,12(4)
Quantum wire (QWR) heterostructures suitable for optoelectronic applications should meet a number of requirements, including defect free interfaces, large subband separation, long carrier lifetime, efficient carrier capture. The structural and opticl properties of GaAs/AlGaAs and InGaAs/GaAs quantum wire (QWR) heterostructures grown by organometallic chemical vapor deposition on nonplanr substrates, which satisfy many of these criteria, are described. These crescent-shaped QWRs are formed in situ during epitaxial growth resulting in virtually defect free interfaces. Effective wire widths as small as 10nm have been achieved, corresponding to electron subband separations greater than KBT at room temperature. The enhanced density of states at the QWR subbands manifests itself in higher optical absorption and emission as visualized in photoluminescence (PL), PL excitation, amplified spontaneous emission and lasing spectra of these structures. Effective carrier capture into the wires via connected quantum well regions, which is important for enhancing the otherwise extremely small capture cross section of these wires, has also been observed. Room temperature operation of GaAs/AlGaAs and strained InGaAs/GaAs QWR lasers with threshold currents as low as 0.6mA has been demonstrated. 相似文献
992.
Zboril R. Mashlan M. Machala L. Walla J. Barcova K. Martinec P. 《Hyperfine Interactions》2004,156(1-4):403-410
Hyperfine Interactions - The natural garnets from almandine (Fe3Al2Si3O12)–pyrope (Mg3Al2Si3O12) series with the iron to magnesium atomic ratio ranging from 0.2 to 1 were characterised and... 相似文献
993.
R. Kudrawiec M. Syperek J. Misiewicz R. Paszkiewicz B. Paszkiewicz M. Tlaczala 《Superlattices and Microstructures》2004,36(4-6):633
Undoped AlGaN/GaN heterostructures with different content and thickness of AlGaN layer are investigated by photoreflectance (PR) spectroscopy. We have observed PR resonances related to an absorption in both GaN and AlGaN layers. The character of these resonances has been analyzed, and PR lines associated with excitonic and band-to-band absorption in the GaN layer and band-to-band absorption in the AlGaN layer have been identified. The transition related to band-to-band absorption possesses characteristic Franz–Keldysh oscillations (FKOs) associated with a built-in electric field. The electric field in the AlGaN layer obtained on the basis of the analysis of FKOs has been found to be in the range of 244–341 kV/cm. The value of the field has been found to decrease with the increase in AlGaN thickness and to increase with the increase in Al concentration. The surface potential for AlGaN layers has been found to increase with the increase in Al mole fraction and has been estimated to be in the range of 1.0–1.7 eV. 相似文献
994.
Design theory crosses the boundary between mathematics and statistics, and includes a wide range of disparate types of design. In this paper we present a classification scheme which aims to include as many important types as possible, based on a balance among concept, representation and use. 相似文献
995.
996.
A. Heidenreich I. Schek D. Scharf J. Jortner 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):227-229
The time resolved dynamics of diffusionless cube → ring isomerization of the Na4Cl4 cluster was interrogated by constant energy molecular dynamics simulations, utilizing the first passage time method. The nonreactive isomerization induced by nonselective vibrational excitation is well accounted for in terms of the statistical RRK theory, opening avenues for experimental exploration of time-resolved cluster isomerization dynamics. 相似文献
997.
998.
Robert G. Payton 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,44(6):876-888
A cylindrically orthotropic elastic solid is excited by a point impulsive body force. The solid contains a semi-infinite stress
free crack. The resulting anti-plane wave motion problem has been solved in the form of a finite series representing the incident
and reflected pulses plus an integral representing the diffraction pulse. The series part of the solution has been previously
treated. In the present investigation the diffraction integral is integrated when λ (which measures the anisotropy of the
solid) is an odd integer number. The diffraction integral is also integrated when λ is half an odd integer, for the special
case in which the source lies in the plane of the crack and parallel to the crack edge. The displacement jump across the circular
diffraction wave front is given for unrestricted (positive) values of λ. 相似文献
999.
We give a number of characterizations of bodies of constant width in arbitrary dimension. As an application, we describe a way to construct a body of constant width in dimension n, one of its (n – 1)‐dimensional projection being given. We give a number of examples, like a four‐dimensional body of constant width whose 3D‐projection is the classical Meissner's body. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
1000.
A. V. Govorkov A. Ya. Polyakov T. G. Yugova N. B. Smirnov E. A. Petrova M. V. Mezhennyi A. V. Markov I. -H. Lee S. J. Pearton 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(4):380-385
The relation between the density of etch pits revealed in GaN by etching in a KOH/NaOH eutectic and the density of dislocations determined by transmission electron microscopy (TEM) is studied along with the relation between the density of dislocations and the density of dark spot defects observed in GaN by microcathodoluminescence (MCL) and electron-beam-induced current (EBIC). It is demonstrated that selective etching is a reliable rapid method for the determination of the type and density of dislocations in GaN in the range 106–108 cm?2, while MCL and EBIC can be used for the rapid nondestructive determination of the density of dislocations in the range 106–108 cm?2. It is also found that some deep electron and hole traps are related to dislocations. 相似文献