bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hole subband structure in single and double p‐type δ ‐doped diamond quantum wells
Authors: Rodríguez‐Vargas I. , Duque C. A. , Mora‐Ramos M. E. , Velasco V. R. 
Published: February 2007

AbstractHeavy, light, and split‐off hole states in single and double p‐δ ‐doped diamond quantum wells are studied with the use of a 6 × 6 k·p model. The effective mass Hamiltonian is solved using a local density Thomas‐Fermi‐Dirac approximation for the description of the band bending pro.le. The features of the valence band spectrum are brie.y discussed in both cases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acceptor and donor impurity‐related optical absorption spectra in double quantum wells: electric field and hydrostatic pressure effects
Authors: Morales A. L. , Raigoza N. , Duque C. A. 
Published: February 2007

AbstractThe hydrostatic pressure and applied electric field dependencies on the shallow‐impurity related optical absorption spectra in GaAs‐Ga1–x Alx As double quantum wells are calculated. Results are obtained for different well and barrier widths. A pressure dependent blue‐shift and electric field dependent read‐shift in the absorption spectra have been described for two different cases of symmetrical double quantum well systems. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative study of the hydrostatic pressure and temperature effects on the impurity‐related optical properties in single and double GaAs–Ga1–xAlxAs quantum wells
Authors: Odhiambo Oyoko H. , Porras‐Montenegro N. , López S. Y. , Duque C. A. 
Published: February 2007

AbstractUsing a variational technique within the effective mass approximation we have carried out a comparative study of the effect of hydrostatic pressure and temperature on the shallow‐impurity related optical absorption spectra in GaAs‐Ga1–x Alx As single and double quantum wells. The results show a pressure dependent read‐shift and a temperature dependent blue‐shift in the optical absorption spectra. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of humidity and acetone on the optical and electrical properties of porous silicon nanostructures
Authors: Erdamar O. , Bilen B. , Skarlatos Y. , Aktas G. , Inci M. N. 
Published: February 2007

AbstractPorous silicon (P‐Si) is a suitable material for applications in gas sensors, biomedical sensors and optical sensors. In this work, the effects of humidity and acetone on the optical and electrical properties of porous silicon nanostructures, produced by two different methods, are studied. The first method is stain etching of silicon wafers by evaporation of hydrogen fluoride (HF) based etchant. The second method is the electrochemical anodization of silicon wafers at low current densities in HF‐based solutions under white light. Electrical conduction mechanism of P‐Si samples is examined through AC and DC measurements. It is observed that the I‐V response of the samples shows a rectifying behaviour that is dependent on the ambient relative humidity (rh). AC measurements show that such samples are quite capacitive and this behaviour shows a very little dependence on the relative humidity. Photoluminescence (PL) spectroscopy measurements are performed with pumping the samples with laser wavelengths of 313.8 nm and 365.6 nm. The PL peak position is observed between 600‐650 nm, depending on the sample preparation conditions. The intensity of the luminescence decreases by time and the peak wavelength makes a red‐shift due to oxidation. Photoluminescence spectroscopy measurements are also repeated after exposing the samples to water and acetone. It is observed that water decreases the luminescence intensity very little and causes a slight red‐shift while acetone decreases the intensity more and causes no important shift in the peak wavelength. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of spin‐qubit operation in coupled quantum dots
Authors: Goto Daisuke , Eto Mikio 
Published: February 2007

AbstractElectronic states and spin operation in coupled quantum dots are numerically studied, considering realistic shape of quantum dots and electron‐electron interaction. (i) We evaluate the spin coupling J between two electron spins, as a function of magnetic field perpendicular to the quantum dots. We observe a transition from antiferromagnetic coupling (J > 0) to ferromagnetic coupling (J < 0) at magnetic field of a few Tesla. The spin coupling is hardly influenced by the size difference between the quantum dots if the energy levels are matched. (ii) We simulate SWAP gate operations by calculating the time development of two electron spins. We show that a sudden change of tunnel barrier may result in the gate errors. The spin exchange is incomplete in the presence of strong spin‐orbit interaction in InGaAs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cluster expansion failings when applied to semiconductor superlattices
Authors: Ferreira L. G. , Marques M. , Teles L. K. 
Published: February 2007

AbstractCluster expansions (CE), by dealing only with short‐range interactions, become inadequate when the interaction in the alloy is of long range. The classical example is the Madelung interaction (electrostatic energy) which, by decaying slowly with distance (1/r) cannot be described with any precision by CEs. Fortunately, in the case of semiconductors, charge neutrality is attained after a few atoms so that no 1/r term propagates far into the lattice. There are other long‐range interactions, the strain energy due to alloying with different atomic sizes (1/r3), for instance, but this not a more important difficulty to CE than other interactions (the screened Coulomb, the exclusion principle, etc), as it will be shortly seen. In the case of semiconductors, an important test for CEs is how well they can perform with superlattices. This problem was studied before, at a time when the CE techniques were not so well developed. In what follows we show the results of several different CE applications to the wurtzite‐based Ga1–x Alx N alloy system and to a model of strain energy, paying special attention to the superlattices and the special quasirandom structures SQS (A. Zunger, S.‐H. Wei, L.G. Ferreira and J.E. Bernard, Phys. Rev. Lett 65, 353 (1990)). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron tunneling/scattering through a QPC saddle potential in crossed electric and magnetic fields
Authors: Fessatidis V. , Horing N. J. M. , Sabeeh K. , Yar A. , Glasser M. L. 
Published: February 2007

AbstractElectron transmission through a quantum point contact (QPC) in the presence of both electric and magnetic fields is examined. The QPC is modeled as a saddle potential. To start, we derive the relevant Green's function including the effects of arbitrarily time‐dependent electric and constant magnetic fields using Schwinger's operator equation of motion approach. We then apply it to determine transmission of the electron guiding center through the QPC in constant electric and magnetic fields. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of carriers on magnetization relaxation in (Cd,Mn)Te quantum wells
Authors: Goryca M. , Ferrand D. , Kossacki P. , Nawrocki M. , Pacuski W. , Maslana W. , Tatarenko S. , Wojtowicz T. , Karczewski G. , Cibert J. 
Published: February 2007

AbstractThe relaxation of the magnetization after a short pulse of magnetic field in n‐doped and p‐doped (Cd,Mn)Te quantum wells is determined from the giant Zeeman shift of the photoluminescence and transmission lines. This technique allows us to investigate the magnetization dynamics in zero field. In n‐doped samples the magnetization relaxation is found to be faster than 20 ns. In case of p‐doped samples two components of relaxation are observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐quantum transport in AlxGa1–xAsySb1–y/InAs quantum wells
Authors: Ishida S. , Fujimoto A. , Tamiya S. , Oto K. , Okamoto A. , Shibasaki I. 
Published: February 2007

AbstractMagneto‐quantum transport properties in AlxGa1–xAsySb1–y/InAs deep quantum wells (QWs) with different well width (Lw = 15 and 50 nm) have been studied both in low and high magnetic fields. The low‐field magnetoconductance has been explained in the light of the two‐dimensional weak‐localization theory taking account of the effect of Zeeman splitting on spin‐orbit scattering of electrons. Analysis of Quantum Hall effect (QHE) in high‐field region for Lw = 50 nm indicates the existence of a small number of holes only partially participating with the QHE, suggesting that our QW is a type‐II hetero‐structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Examination of the optical transmission through metallic nano‐apertures
Authors: Kim Y. C. , Choi S. S. , Joo M. , Shresta S. , Suwal O. , Park M. J. , Kim D. W. 
Published: February 2007

AbstractThere have been tremendous interests about the near‐field optical effect through a sub‐wavelength size metallic aperture. In this report, the computational experiments using the finite‐difference time‐domain (FDTD) method has been performed to examine the optical transmission intensity through the small apertures. In the case that the aperture size is very large compared with the wavelength of the light, the diffracted angle is small and the perpendicular component of the propagation vector is greater than the parallel component of the propagation vector. With decreasing the aperture diameter, the diffraction angle becomes greater and the parallel component of the propagation vector becomes greater. For the aperture diameter smaller than the wavelength of the incident light, the conventional diffraction formula no longer becomes valid. The FDTD simulations are performed to obtain the light intensity distribution transmitted through the various diameters of the apertures. In addition, the FDTD simulation is also carried out to examine the characteristics of the apertures on double layer metallic plate structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A theoretical investigation of carrier and optical mode confinement in GaInNAs QWs on GaAs and InP substrates
Authors: Gönül B. , Köksal K. , Bakır E. 
Published: February 2007

AbstractBoth carrier and optical mode confinements are the basic ingredients while designing the semiconductor quantum well lasers. The former strongly depends on the band offsets of the heterostructure and the latter is mainly associated with the difference in the refractive index between the wave guiding core and the cladding layers. It is known that refractive index strongly depends on the direct band gap of the semiconductor material and the band gap of the III‐N‐V semiconductor layer can be engineered by means of adding nitrogen into InGaAs. We investigate, in this work, the refractive indices and the corresponding optical confinement factors of the proposed III‐N‐V laser material systems on GaAs and InP substrates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton spin dynamics in ZnO epilayers
Authors: Lagarde D. , Lombez L. , Balocchi A. , Renucci P. , Carrère H. , Amand T. , Marie X. , Mei Z. X. , Du X. L. , Xue Q. K. 
Published: February 2007

AbstractWe used time‐resolved optical orientation experiments to study the low temperature spin dynamics of a ZnO epilayer. The sample shows a circular polarisation of the donor‐bound exciton of 11% with a decay time of 275 ps. A very narrow spectral dependence of the initial polarisation and a rapid decrease of the polarisation decay time with temperature are also observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of nanoporous Al2O3 obtained by aluminium anodization
Authors: Green S. , Badán J. A. , Gilles M. , Cortes A. , Riveros G. , Ramírez D. , Gómez H. , Quagliata E. , Dalchiele E. A. , Marotti R. E. 
Published: February 2007

AbstractThe optical properties of nanoporous alumina (Al2O3) prepared by electrochemical anodization of aluminum foils are studied. The samples show an ordered array of nanometric sized pores. Their reflectance spectra show an absorption edge in the UV that shifts into the visible with anodization temperature. A strong photoluminescence (PL) in the blue‐green spectral range is also shown. The PL spectra shift in the same direction as the reflectance. The PL spectra were also measured at low temperatures. The results are best interpreted assigning the PL to oxygen vacancies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electroless nickel deposition onto silicon surfaces for micro and nanoelectronics applications and microtechnology processes
Authors: Marques A. E. B. , Santos Filho S. G. , Martini S. 
Published: February 2007

AbstractWe studied and characterized the processes of electroless nickel deposition in order to use it in microelectronics and microtechnology. We perform electroless nickel deposition on silicon surfaces with acid solution on palladium preactivated surfaces as well as alkaline solution without palladium preactivation. Electroless deposition was also performed on aluminum surfaces, deposited by evaporation onto silicon oxide. MOS capacitors were also fabricated to perform electrical characterizations of the structure (nickel‐aluminium‐oxide‐silicon) using capacitance‐voltage plots (C‐V curves). In addition, we also presented the use of electroless nickel deposition for chemical sensors which were fabricated using conventional microelectronics techniques. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mesoscopic Fano effect in an Aharonov‐Bohm interferometer Coulomb‐coupled to a nearby quantum dot
Authors: Ţolea M. , Moldoveanu V. , Tanatar B. 
Published: February 2007

AbstractMotivated by the pionieering experiments of Buks et al. [Nature 391, 871 (1998)] we investigate the visibility of the Fano effect in a single‐dot Aharonov‐Bohm interferometer which is Coulomb‐coupled to a nearby quantum dot. The latter acts as a ‘Which Path Detector’ and is coupled to two leads on which a finite bias is applied. Using the non‐equilibrium Keldysh‐Green function formalism we compute the currents through the detector and the interferometer. We take into account the first two contributions to the interaction selfenergy and emphasize the correction to the Landauer formula which appears beyond the single‐particle approximation. Particular attention is given to the coherence properties of the interferometer in the presence of the electron‐electron interaction between the embedded dot and the detector. We show that when the detector is subjected to a finite bias the amplitude of Aharonov‐Bohm oscillations of the current through the interferometer decreases. The Fano line is in turn rather stable under interaction. Our results generalize an earlier work of Silva and Levit [Phys. Rev. B 63, 201309 (2001)] and complement the existing description of the controlled dephasing. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of cylindrical interfaces
Authors: Nobre Eloneid F. , Vilela Rivelino C. , Farias Gil A. , Almeida Nilson N. 
Published: February 2007

AbstractWe are interested in the study of the optical properties of cylindrical interfaces by the analysis of the propagation of energy and power in coaxial cylinders. The numerical results are obtained for the surface polaritons propagating in semiconductors coaxial cylinders made of GaN and AlN. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conductance fluctuations in a MOSFET
Authors: Jimenez‐Montecinos J. , Martínez‐Mares M. , Pereyra P. 
Published: February 2007

AbstractWe study the transport properties in a narrow MOSFET device, which consists of a two dimensional electronic waveguide, with an electric field applied in the transverse direction. Based on recent solutions of the Schrödinger equation for this system, we analyze the conductance fluctuations as a function of the electric field (the gate voltage), and of the Fermi energy. The statistical analysis of these fluctuations shows that the multichannel Poisson kernel description is valid also for this non‐chaotic system. Besides the technological interest on MOSFET devices, it allows us to understand more fundamental quantities like the scattering properties of integrable systems. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excited states and spontaneous transition lifetimes of donor impurities in quantum dots
Authors: Murillo G. , Arce Julio C. , Duque C. A. , Porras‐Montenegro N. 
Published: February 2007

AbstractWe calculate the 2p→1s‐like transition energy and the spontaneous lifetime of an on‐center shallow donor impurity in a spherical parabolic GaAs‐(Ga,Al)As quantum dot (PQD) as a function of the radius of the structure and the strength of an applied electric field. In our calculations we use a variational method, within the effective mass and dipolar approximations. We find that the spontaneous lifetimes increase with the radius of the PQD and the applied electric field. In this direction our results revel that the electric field can be used to suppress the electron‐phonon interaction driving to the increasing of the 2p‐1s spontaneous life‐time, showing the feasibility of using impurity states to be used in quantum computing developments. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical spin injection in InAs/GaAs p‐doped quantum dots through Co/Al2O3/GaAs tunnel barrier
Authors: Lombez L. , Braun P. F. , Renucci P. , Gallo P. , Carrère H. , Binh P. H. , Marie X. , Amand T. , Gauffier J. L. , Urbaszek B. , Arnoult A. , Fontaine C. , Deranlot C. , Mattana R. , Jaffrès H. 
Published: February 2007

AbstractWe have demonstrated by CW electroluminescence the ability to inject spin polarized electrons through Co/Al2O3/GaAs structures into p‐doped InAs/GaAs quantum dots embedded in a PIN GaAs light emitting diode. The spin relaxation processes in the p‐doped quantum dots are characterized independently by optical measurements (time and polarization–resolved photoluminescence). The measured electroluminescence circular polarization is about 15% at 1.7 K in a 2 T magnetic field, leading to an estimation of the electrical spin injection yield of about 35%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron‐hole complexes localized on the quantum well interface roughnesses
Authors: Semina M. A. , Sergeev R. A. , Suris R. A. 
Published: February 2007

AbstractThe localization of two‐dimensional electron‐hole complexes on the attractive potential of an arbitrary shape is studied theoretically. General method of a simple and vivid trial function construction for calculation of the ground state binding energy for such complexes is suggested. The limiting cases corresponding to different relations between characteristic parameters are analyzed. The developed method is illustrated by the particular calculations for the case of exciton in two‐dimensional quantum well with an additional lateral con.nement potential. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐organized quantum dot superlattice inside silica mesoporous material
Authors: Sugimoto N. , Funabashi H. , Mitsushima Y. 
Published: February 2007

AbstractThree‐dimensional quantum dot superlattices were synthesized by self‐assemble process method with silica mesoporous thin films. The diameter (3.8 nm) and position of metal quantum dots can be designed by the crystal morphology of silica mesoporous film which have Pm3n cubic symmetry. The diameter and arrangement of dots were strictly controlled by host materials. The I‐V characteristics and time‐dependent current oscillation were measured with sub‐micron contacts to metal superlattices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance study of SQW GaInNAs Fabry‐Perot lasers
Authors: Tiras E. , Hepburn C. J. , Balkan N. , Saarinen M. , Pessa M. , Jouhti T. 
Published: February 2007

AbstractThe work presented here is concerned with studies of the operational characteristics of single‐quantum‐well GaInNAs/GaAs Fabry‐Perot lasers, where identical layer structures with differing cavity lengths are evaluated both experimentally and theoretically. Standard techniques are used to determine the temperature dependence, in the pulsed mode, of I‐V, L‐I and spectral electroluminescence. Important parameters, such as the threshold current and T0, are determined and tabulated for all the structures. The differential and internal quantum efficiency and hence the internal losses for each of the lasers are obtained from the experimental data. The latter is compared with the gain spectra measured using the Hakki‐Paoli method and calculated from a simple theory. From the spectral measurements above the lasing threshold, we obtain the temperature dependence of the GaInNAs quantum well effective gap as 0.3 meV/K, which is in good agreement with results published by other groups. However, a better fit is obtained using the Varshni temperature dependence using values of E0 = 1.058 eV, α = 4.8 × 10–4 eVK‐2, β = 284 ± 167 K. To put our results in perspective, we also present an up‐to‐date review of similar SQW lasers and suggest improvements to the current structure for enhanced threshold and power characteristics. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of electric field on recombination of self‐trapped excitons in silicon nanocrystals
Authors: Vandyshev E. N. , Zhuravlev K. S. 
Published: February 2007

AbstractStudy of the effect of an external electric field on photoluminescence (PL) of silicon nanocrystals formed in SiO2 has been carried out. It was found that the electric field results in a red shift of PL band and a decrease of the PL intensity at any temperature in the range of 5‐290 K. A decay time of PL intensity after pulse excitation does not depend on the electric field strength. The experimental data are explained in framework of the model of recombination of self‐trapped excitons formed at nanocrystal‐matrix boundary. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of a double quantum dot structure by stimulated Raman adiabatic passage
Authors: Voutsinas Evangelos , Boviatsis John , Fountoulakis Antonios 
Published: February 2007

AbstractIn this work we study the potential for coherent manipulation of an asymmetric double quantum dot structure by the use of adiabatic methods. These methods are the Stimulated Raman Adiabatic Passage (STIRAP) and its modification the fractional STIRAP. We show that such a method can be used for complete electron transfer between the two lower states of the quantum dots. In addition, with fractional STIRAP a coherent superposition of the two lower states of the quantum dots can be created. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advanced modelling of GaN/AlGaN HEMT devices with field plate
Authors: Brannick A. , Zakhleniuk N. , Ridley B. K. , Eastman L. F. , Schaff W. J. , Shealy J. R. 
Published: February 2007

AbstractIn this paper we carry out detailed study and numerical modelling of the operation of the GaN/AlGaN High Electron Mobility Transistor (HEMT) with Field Plate (FP) optimisation. The FP has the effect of smoothing the potential gradient along the HEMT channel near the gate edge on the drain side, resulting in the enhancement of the breakdown voltage. We show that the main effect of the FP is a substantial decrease in the longitudinal component of the field EL, along with little variation of the normal component ET. In addition to the main peak of the EL field at the gate edge, there is a secondary peak under the FP edge which grows rapidly with drain bias and eventually surpasses the first. The appearance of the second peak should be taken into account in optimising of the HEMT design. The I‐V characteristics of the FP‐gated device remain practically the same as those of a device without a FP. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)