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Suche nach „[J.] [Fatah]“ hat 7 Publikationen gefunden
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    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Thomas Stirner, P. Harrison, W. Hagston, J.H.C. Hogg, J. Fatah

    Double crystal x-ray diffraction simulations of diffusion in semiconductor microstructures

    Journal of Applied Physics, vol. 83, pp. 4037-4041

    1998

    DOI: 10.1063/1.367159

    Abstract anzeigen

    Diffusion in group IV, III-V and II-VI semiconductors is an interesting problem not only from a fundamental physics viewpoint but also in practical terms, since it could determine the useful lifetime of a device. Any attempt to control the amount of diffusion in a semiconductor device, whether it be a quantum well structure or not, requires an accurate determination of the diffusion coefficient. The present theoretical study shows that this could be achieved via x-ray diffraction studies in quantum well structures. It is demonstrated that the rocking curves of single quantum wells are not sensitive to diffusion. However the intensity of the first order satellite, which is characteristic of superlattice rocking curves, is strongly dependent upon diffusion and it is proposed that this technique could be used to measure the diffusion coefficient D.

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    Zeitschriftenartikel

    P. Harrison, W. Hagston, Thomas Stirner, J. Fatah

    Alloy nonrandomness in diluted magnetic semiconductors

    Journal of Applied Physics, vol. 79, pp. 1684-1688

    1996

    DOI: 10.1063/1.360954

    Abstract anzeigen

    A simple model of alloy nonrandomness is introduced within a framework where the effective concentration of spin singlets as a function of the nominal concentration of magnetic ions in a nonrandom alloy can be obtained by transformations of the corresponding function in random alloys. The theory shows that a given system that is appreciably nonrandom can have a magnetic response almost identical with that of a random distribution. Possible ways of identifying alloy nonrandomness in diluted magnetic semiconductor structures are described.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Vortrag

    J. Fatah, I. Karla, J.H.C. Hogg, P. Harrison, W. Hagston, Thomas Stirner

    Defect induced diffusion mechanisms in ion implanted quantum well structures

    Posterpräsentation

    22nd International Conference on the Physics of Semiconductors (ICPS22), Vancouver, Kanada

    1994

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    J. Fatah, I. Karla, J.H.C. Hogg, P. Harrison, W. Hagston, Thomas Stirner

    Defect induced diffusion mechanisms in ion implanted quantum well structures

    Proceedings of the 22nd International Conference on the Physics of Semiconductors (ICPS22)

    1994

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    P. Harrison, W. Hagston, T. Piorek, Thomas Stirner, J. Fatah

    Numerical simulation of antiferromagnetic spin-pairing effects in diluted magnetic semiconductors and enhanced paramagnetism at interfaces

    Physical Review B - condensed matter and materials physics, vol. 49, pp. 10341-10344

    1994

    DOI: 10.1103/PhysRevB.49.10341

    Abstract anzeigen

    A numerical simulation of the antiferromagnetic spin pairing of neighboring magnetic ions within a diluted magnetic semiconductor is presented. Utilizing a random distribution of the magnetic ions requires the inclusion of nearest-neighbor interactions only in order to give agreement with the low-field bulk-magnetization properties observed experimentally. However, the latter are shown to be a relatively insensitive measure of the degree of ordering in the alloy system, and the experimental results could equally well be accounted for by assuming appreciable alloy clustering. The simulations also show that there is an enhancement in the paramagnetism associated with the interface layers in a quantum-well structure.

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    Zeitschriftenartikel

    P. Harrison, W. Hagston, T. Piorek, Thomas Stirner, J. Fatah, R. Roberts, D. Ortega, A. Chesworth

    Monte Carlo simulations of carrier transport and relaxation in superlattices

    Superlattices and Microstructures, vol. 15, no. 2, pp. 209-213

    1994

    DOI: 10.1006/spmi.1994.1042

    Abstract anzeigen

    Monte Carlo simulations of carrier transport through an undoped superlattice into an extended well are described. The results illustrate clearly the important role played by LO phonons in relaxing the energy and the desirability of designing structures which minimize the need for acoustic phonon participation. Attention is drawn to the fact that although, for the standard structures investigated, the LO phonon relaxation rate is relatively independent of the miniband and/or the quantum well eigenstates, the precise shape of the form-factor for an allowed LO transition could play an important role in deciding the relative number of 'slow' carriers in an actual system.

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    Zeitschriftenartikel

    P. Harrison, W. Hagston, T. Piorek, Thomas Stirner, J. Fatah, R. Roberts

    Effects of interfaces and interface roughness in diluted magnetic semiconductor microstructures

    Superlattices and Microstructures, vol. 16, no. 1, pp. 11-15

    1994

    DOI: 10.1006/spmi.1994.1100

    Abstract anzeigen

    In this work a numerical model of anti-ferromagnetic spin-pairing in diluted magnetic semiconductors is used to determine the paramagnetic behaviour of both abrupt and rough interfaces. A detailed study of the paramagnetic behaviour of the individual monolayers adjacent to an abrupt interface with a non-magnetic material has not only predicted quantitatively the enhanced paramagnetism in the ultimate monolayer, it has also predicted a depressed paramagnetism in the penultimate monolayer. Furthermore, the results of the theoretical model have been compared with experimental observations in order to gain insight into intrinsic and structural properties of heterojunctions in diluted magnetic semiconductors.