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Scattering Mechanism (scattering + mechanism)
Selected AbstractsQuantum transport in high mobility AlGaN/GaN 2DEGs and nanostructuresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006S. Schmult Abstract High mobility two-dimensional electron systems in GaN/AlGaN heterostructures have been realized by plasma assisted molecular beam epitaxy on GaN templates. In the density range of 1011 cm,2 to 1012 cm,2, mobility values exceeding 160000 cm2/Vs have been achieved. Scattering mechanisms that presently limit the production of higher mobility samples are discussed. We present results of a systematic study of the weak localization and antilocalization corrections to the classical conductivity at very low magnetic fields. The unambiguous observation of a conductivity maximum at B = 0 suggests that spin,orbit scattering is not negligible in GaN heterostructures as one might expect for a wide-bandgap system. We have recently realized electron transport through GaN nanostructures. We report on the transport properties of the first quantum point contacts (QPCs) in GaN. These devices are used to study one-dimensional transport in the Nitride system. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Atomistic analysis of B clustering and mobility degradation in highly B-doped junctionsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4-5 2010Maria Aboy Abstract In this paper we discuss from an atomistic point of view some of the issues involved in the modeling of electrical characteristics evolution in silicon devices as a result of ion implantation and annealing processes in silicon. In particular, evolution of electrically active dose, sheet resistance and hole mobility has been investigated for high B concentration profiles in pre-amorphized Si. For this purpose, Hall measurements combined with atomistic kinetic Monte Carlo atomistic simulations have been performed. An apparent anomalous behavior has been observed for the evolution of the active dose and the sheet resistance, in contrast to opposite trend evolutions reported previously. Our results indicate that this anomalous behavior is due to large variations in hole mobility with active dopant concentration, much larger than that associated to the classical dependence of hole mobility with carrier concentration. Simulations suggest that hole mobility is significantly degraded by the presence of a large concentration of boron-interstitial clusters, indicating the existence of an additional scattering mechanism. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hole,polar phonon interaction scattering mobility in chain structured TlSe0.75S0.25 crystalsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009A. F. Qasrawi Abstract In this study, the electrical resistivity, charge carriers density and Hall mobility of chain structured TlSe0.75S0.25 crystal have been measured and analyzed to establish the dominant scattering mechanism in crystal. The data analyses have shown that this crystal exhibits an extrinsic p-type conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of three energy levels located at 280 meV, 68 meV and 48 meV. The temperature dependence of carrier density was analyzed by using the single donor,single acceptor model. The carrier concentration data were best reproduced assuming the existence of an acceptor impurity level being located at 68 meV consistent with that observed from resistivity measurement. The model allowed the determination of the hole effective mass and the acceptor,donor concentration difference as 0.44m0 and 2.2 × 1012 cm,3, respectively. The Hall mobility of the TlSe0.75S0.25 crystal is found to be limited by the scattering of charged carriers over the (chain) boundaries and the scattering of hole,polar phonon interactions above and below 300 K, respectively. The value of the energy barrier height at the chain boundaries was found to be 261 meV. The polar phonon scattering mobility revealed the high-frequency and static dielectric constants of 13.6 and 15.0, respectively. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Study of the electrical conductivity and thermoelectric power of In2Te5 single crystalsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003M. M. Nassary Abstract In the present study, single crystals of defect semiconductor In2Te5 were grown by the Bridgman technique. An investigation was made on the Hall effect, electrical conductivity and thermoelectric power of In2Te5 monocrystal in the temperature ranging from 200 to 500 K. The investigated samples were P-type conducting. The Hall coefficient yields a room-temperature carrier concentration of (7.7 × 109 cm,3). The bandgap was found to be (,Eg = 0.993 eV). Hence, a combination of the electrical conductivity and Hall effect measurements enable us to study the influence of temperature on the Hall mobility (,) and to discuss the scattering mechanism of the charge carriers, also the present investigation involves thermoelectric power measurements of In2Te5 single crystal: these measurements enable us to determine many physical parameters such as carriers mobilities, effective masses of free charge carriers (mp*, mn*, diffusion coefficients (Dp, Dn) and diffusion lengths as well as the relaxation time (,p, ,n). (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Understanding quantum dots: overheating of the LO-phonon modesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007K. Král Abstract Longitudinal optical phonons have been used recently to explain the electronic energy relaxation in quantum dots. In this theory they served as a reservoir, on which the electron executes multiple scattering acts. Rather naturally such a phonon subsystem is expected to be passive, namely, in a long-time limit of development the whole system should be able to achieve such a stationary state in which statistical distributions of both subsystems, electron and phonons, do not change in time. Here we remind briefly that the recent approach to the relaxation theory in quantum dots displays a non-passivity of such a reservoir. We remind briefly the method of a partial elimination of this phonon overheating effect by using the Lang-Firsov transformation. We apply the modified relaxation theory to the electronic relaxation at low electronic densities in quantum dot systems and come to conclusions about the role of e-LO scattering mechanism in these situations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Multiple sweep method of moments analysis of electromagnetic scattering from 3D targets on ocean-like rough surfacesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007D. Çolak Abstract This paper presents the multiple sweep method of moments (MSMM) analysis of electromagnetic (EM) scattering from three dimensional (3D) targets on ocean-like rough surfaces. The MSMM is a recursive method for solving the large matrix equations which arise in the method of moments (MoM) analysis of electrically large bodies. In the MSMM, the body is split into P sections and the currents on these sections are found in a sequential downrange-uprange fashion. The first sweep includes the dominant scattering mechanisms and each subsequent sweep includes higher order mechanisms. The results obtained from this study demonstrate that the MSMM is a very reliable and efficient tool for the analysis of this class of problems. The numerical results yield insight into electromagnetic scattering mechanisms associated with a 3D target on a rough surface, and provide accurate and robust reference solutions for more approximate techniques which can handle larger geometries more efficiently. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 241,247, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22074 [source] Exciton relaxation in bulk wurtzite GaN: the role of piezoelectric interactionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003G. Kokolakis Abstract A theoretical study on the relaxation of coupled free carriers and excitons after non-resonant optical excitation in bulk wurtzite GaN is presented. In particular the effect of the acoustic piezoelectric scattering is taken under consideration, and the respective rates have been calculated, including screening effects. Results show that the piezo-acoustic rates are bigger in the wurtzite phase of GaN with respect to the cubic phase, and they are really sensitive to the background doping of the sample. Simulations of the full dynamics of the system are performed by using an Ensemble Monte Carlo method under which all the relevant scattering mechanisms are included. The set of semiclassical Boltzmann equations for electron and hole populations is complemented by an additional equation for the exciton distribution and is coupled by reaction terms describing phonon-mediated exciton binding and dissociation. The temporal evolution is studied in the short range time (100 ps) after photo-excitation. It shows that a high background doping prevents the electrons to relax toward low energy states. [source] Excitation of millimeter-wave oscillations in InAlAs/InGaAs heterostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008S. Pérez Abstract We study the origin of strong Terahertz (THz) oscillations taking place in InAlAs/InGaAs slot diodes - base of High Electron Mobility Transistor (HEMT) devices - when bias surpasses 0.5 V. To this end we perform a microscopic analysis of current fluctuations, calculated by means of an ensemble Monte Carlo (MC) simulator. The millimeter and submillimeter waves are caused by the presence of Gunn-like oscillations whose dynamics is controlled by ballistic , valley electrons in the channel. These carriers are capable to reach extremely high velocities due to the influence of degeneracy effects (preventing scattering mechanisms) and the presence of a recessed geometry. The dependence of this process on the recess and recess-drain lengths is analyzed in order to improve the frequency and magnitude of the oscillations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||