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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Physics, Section A 351 (1981), S. 142-156 
    ISSN: 0375-9474
    Keywords: Nuclear Reactions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5567-5579 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ballistic electron wave propagation through discontinuous finite-potential electron waveguides is analyzed. The wave function in each uniform waveguide section surrounding a discontinuity is represented as a sum of the local eigenmodes of that section, and both propagating and evanescent modes arising from bound and discretized continuum states are included in the expansion. The local eigenmodes are found using a transfer-matrix technique that allows the mode-matching across discontinuities to be calculated efficiently. A scattering matrix formalism is used to cascade multiple discontinuities and extract the current reflection and transmission characteristics. The method is shown to be accurate and efficient. The discontinuity analysis is applied to waveguides induced by split gates over two-dimensional electron gases. An analytical method is developed to approximate the potential energy profile produced by arbitrary-shaped gates as a function of gate voltage and material parameters. Simulation of a gate-induced constriction (quantum point contact) shows that the conductance as a function of gate voltage exhibits smooth quantized steps without oscillations in agreement with published experimental results.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3352-3366 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron wave directional coupling between parallel semiconductor electron waveguides is analyzed by calculating the supermode (superposition of eigenmodes) of the complete structure. A transfer-matrix technique is used to calculate the eigenmodes of multiple-layer structures having arbitrary potential-energy/effective-mass profiles that form the coupled electron waveguides. It is shown that the eigenmodes of electron waveguides having spatially varying effective mass satisfy an orthogonality relation that involves the effective-mass profile. As determined by supermode simulations, coupled-mode analyses give inaccurate directional-coupling transfer lengths when the coupling is strong or the electron energy is low. The influence of various parameters and structure asymmetries on the directional coupling process is investigated. It is shown that asymmetry severely decreases the ability to transfer current from one waveguide to the other, except in the case of effective-mass asymmetry where it causes an energy-dependent transfer efficiency. Switching by modulation of the transfer length and the transfer efficiency are discussed and simulated.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transmission and current-voltage characteristics of Ga1−xAlxAs superlattice electron-wave quantum-interference filter/emitter negative differential resistance devices are analyzed with and without the self-consistency requirement. The analysis neglects the scattering effects within the superlattice since it is assumed that it is very thin (less than the electron coherence length). Thus, the calculated characteristics correspond to the ballistic component of the current. For the non-self-consistent calculation the single-band effective-mass time-independent Schroedinger equation is solved. For the self-consistent calculation, the Schroedinger and Poisson equations are solved iteratively until a self-consistent electron potential energy and electron density are obtained. It is shown that suitably designed electron-wave quantum-interference filter/emitters can exhibit strong negative differential resistance in the current-voltage characteristics, similar to those of resonant tunneling diodes. For low-to-moderate (2–30 meV) Fermi energies in the conduction band of Ga1−xAlxAs (Si doping concentration less or equal to 2 × 1018 cm−3) and temperatures near 30 K (in the ballistic transport regime), it is shown that space-charge effects are relatively small and result in a slight shift of the current-voltage and transmission characteristics toward higher bias voltages. In a fashion similar to that occurring in resonant tunneling diodes, the self-consistent field in electron-wave filter/emitter negative differential resistance devices partially screens the positive applied bias. Designs of Ga1−xAlxAs resonant devices with current peak-to-valley ratios of ∼50 as well as nonresonant (not exhibiting negative differential resistance) devices are analyzed. The corresponding electron charge density distributions are also presented. Superlattice electron-wave filter/emitter negative differential resistance devices can be used as high-speed switches, oscillators, and as monoenergetic emitters in electroluminescent devices and photodetectors.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1432-1434 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An asymmetric semiconductor electron wave Fabry–Perot interference filter has been designed with two above-barrier quasibound states for optical transitions. The upper state was designed to have a spatial confinement lifetime greater than three times that of the lower state (which was designed to be less than 100 fs). Such lifetime ratios and magnitudes, which are nearly impossible for below-barrier states, satisfy the criteria required for achieving population inversion. Furthermore, the transitions were designed to have large dipole matrix elements. Absorption measurements at multiple temperatures were used to demonstrate the first bound-to-quasibound transitions in an asymmetric structure. The experimental energies and dipole matrix elements are in agreement with calculated values. This type of structure could represent the basis for a new room-temperature infrared semiconductor laser.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 440-442 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An exact rigorous coupled-wave analysis has been developed to model ballistic electron wave diffraction by gratings with periodic effective mass and/or potential energy variations. Design expressions have been derived to calculate diffracted angles, to identify evanescent orders, and to identify the Bragg condition. Design expressions for Bragg regime (up to 100% diffraction efficiency in a single order) and Raman–Nath regime (high diffraction efficiency divided among multiple orders) diffraction are presented along with example Ga1−xAlxAs grating designs. Design procedures for ballistic electron switches, multiplexers, spectrometers, and electron waveguide couplers are described.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1855-1857 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that finite-potential heterostructure wells, homostructure voltage-induced wells, and heterostructure barriers can act as waveguides for ballistic electrons and that waveguiding is described by a single dispersion relation and can occur at energies above all band edges. The guided mode cutoffs, electron velocity, effective mass, density of states, and ballistic current density (applicable to 2D electron gases) are presented. The maximum ballistic guided current flowing in a given direction for a 10 monolayer Ga0.75Al0.25As/GaAs/Ga0.9Al0.1As waveguide is found to be 2.3 mA per μm of waveguide width–allowing considerably greater currents than in single-mode quantum wires.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Ecological Modelling 74 (1994), S. 139-160 
    ISSN: 0304-3800
    Keywords: Multivariable system
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-0484
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 50 (1989), S. 63-77 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The origins of visible-band linear polarimetry of Algols and objects related to them are reviewed. It is pointed out, not for the first time, that the polarization signals of these systems can vary sporadically by significant amounts. The difficulty of evaluating the interstellar component of the observed polarization is discussed and these components are evaluated anew for each object studied in this paper. With one possible exception, the polarization signals intrinsic to these binaries derive from electron scattering. A well-defined model is applied to the constant and variable (but phase-locked) polarization signals. Limits to the mass associated with a scattering disk in each binary are derived. Within broad limits, concentrations of scattering mass within and above or below the orbital plane are also developed as are the centroid longitudes of these concentrations within the system. It is pointed out that very few measures of visible-band, circular polarization have been made but that cm-wavelength measures of Algol itself have been very informative.
    Type of Medium: Electronic Resource
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