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  • 1.
    Berggren, Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fagerström, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, Mats
    Chalmers Tekniska Högskola.
    Weman, Helge
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Granström, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Wennerström, O
    Chalmers Tekniska Högskola.
    Hjertberg, T
    Chalmers Tekniska Högskola.
    Controlling inter-chain and intra-chain excitations of a poly(thiophene) derivative in thin films1999In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 304, no 1-2, p. 84-90Article in journal (Refereed)
    Abstract [en]

    The decay of photoexcitations in polythiophene chains has been studied in solid solutions of the polymer from room temperature to 4 K. A strong blue shift of the emission spectrum is observed in the polymer blend, as compared to the homopolymer. Dispersion of the polythiophene suppresses the non-radiative processes, which are suggested to be correlated to close contacts of polymer chains. Quantum chemistry modeling of the excited state distributed on two chains corroborate this conclusion.

  • 2.
    Karlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Dupertuis, M.-A.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kapon, E.
    Fractional-dimensional excitonic absorption theory applied to real V-groove quantum wires2004In: 27th International Conference on the Physics of Semiconductors ICPS-27,2004, 2004Conference paper (Other academic)
  • 3.
    Karlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Dupertuis, M.-A.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kapon, E.
    Fractional-dimensional excitonic absorption theory applied to V-groove quantum wires2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 15Article in journal (Refereed)
    Abstract [en]

    A fractional-dimensional approach is applied to a realistic V-groove quantum wire in order to calculate the excitonic absorption spectrum. An excellent agreement is obtained with much more computationally demanding models as well as with experimental photoluminescence excitation data. However, comparison with a full excitonic calculation reveals situations were the concept of fractional dimensions to some extent fails.

  • 4.
    Karlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dupertuis, M.-A.
    Leifer, K.
    Rudra, A.
    Kapon, E.
    Electroluminescence and photoluminescence excitation study of asymmetric coupled GaAs/AlxGa1-xAs V-groove quantum wires2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 4Article in journal (Refereed)
    Abstract [en]

    We have studied systems of asymmetric coupled GaAs V-groove quantum wires p-i-n diodes, in which the electrons and holes are injected into different wires. Despite the use of a 7 nm thick AlGaAs tunnel barrier, and although we demonstrate that holes tunnel more slowly than electrons, we observe a very efficient and fast tunneling between the quantum wires (QWR's). We attribute this to the achievement of a resonance between hole levels in the two QWR's. Photoluminescence excitation experiments are compared with accurate calculations of the excitonic absorption yielding a level of carrier transfer of nearly 100%. Temperature-dependent electroluminescence exhibits clear effects of tunneling up to room temperature but cannot distinguish separate electron/hole tunneling from exciton tunneling.

  • 5.
    Karlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dupertuis, M.-A.
    Leifer, K.
    Rudra, A.
    Kapon, E.
    Electroluminescence of asymmetric coupled GaAs/AlGaAs V-groove quantum wires2003In: 29th International Symposium on Compound Semiconductors ISCS 2002,2002, 2003, p. 183-Conference paper (Refereed)
  • 6.
    Karlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dupertuis, M.-A.
    Leifer, K.
    Rudra, A.
    Kapon, E.
    Electron and hole transfer between two separated GaAs/AlGaAs V-groove quantum wires2003In: 11th International Conference on Modulated Semiconductor Structures MSS-11,2003, 2003Conference paper (Other academic)
  • 7.
    Karlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Leifer, K.
    Rudra, A.
    Kapon, E.
    Carrier tunneling between parallel GaAs/AlGaAs V-groove quantum wires2004In: 27th International Conference on the Physics of Semiconductors ICPS-27,2004, 2004Conference paper (Other academic)
  • 8.
    Karlsson, Fredrik
    et al.
    Ecole Polytechnique Fédérale de Lausanne .
    Weman, Helge
    Ecole Polytechnique Fédérale de Lausanne .
    Leifer, K.
    Ecole Polytechnique Fédérale de Lausanne .
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne .
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne .
    Lyo, S.K.
    Sandia National Laboratories.
    Strongly reduced exciton transfer between parallel quantum wires2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, p. 101108-Article in journal (Refereed)
    Abstract [en]

    Exciton transfer between two parallel GaAs V-groove quantum wires or two planar quantum wells separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence and photoluminescence excitation spectroscopy. It is found that the transfer is strongly reduced between the widely spaced quantum wires as compared with quantum wells. This observation is supported by model calculations, which yield strong dimensionality dependence of the photon-exchange transfer

  • 9. Karlsson, KF
    et al.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dupertuis, MA
    Leifer, K
    Rudra, A
    Kapon, E
    Electrolummescence of asymmetric coupled GaAs/AlGaAs V-groove quantum wires2003In: Institute of Physics Conference Series, ISSN 0951-3248, E-ISSN 2154-6630, Vol. 174, p. 183-186Article in journal (Refereed)
    Abstract [en]

    We have studied systems of asymmetric coupled GaAs V-groove quantum wires, in which the electrons and holes are injected into different wires. Our experimental results indicate efficient electron and hole tunneling, despite a 7 nm thick AlGaAs tunnel barrier. Temperature dependent electroluminescence exhibit clear effects of tunneling up to room temperature but cannot distinguish electron/hole tunneling from exciton tunneling.

  • 10. Lyo, S.K.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Leifer, K.
    Rudra, A.
    Kapon, E.
    Exciton Energy Transfer between Asymmetric Quantum Wires2006In: APS March Meeting,2006, 2006Conference paper (Other academic)
  • 11. Moses, A.F.
    et al.
    Dheeraj, D.L.
    Fimland, B.O.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Micro-photoluminescence study of heterostructured GaAs/AlGaAs and GaAs/GaAsSb nanowires grown by molecular beam epitaxy2008In: 29th International Conference on the Physics of Semiconductors ICPS,2008, 2008Conference paper (Other academic)
  • 12. Moses, A.F.
    et al.
    Hoang, T.B.
    Dheeraj, D.L.
    Fimland, B.O.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Investigation of the structural and optical properties of single GaAs/GaAsSb/GaAs nanowire quantum dots2008In: 17th International Laser Physics Workshop,2008, 2008Conference paper (Other academic)
  • 13.
    Palmgren, Susanna
    et al.
    Ecole Polytechnique Fédérale de Lausanne .
    Weman, Helge
    Ecole Polytechnique Fédérale de Lausanne .
    Schoenberg, A.
    Ecole Polytechnique Fédérale de Lausanne .
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne .
    Dupertuis, M.-A.
    Ecole Polytechnique Fédérale de Lausanne .
    Leifer, K.
    Ecole Polytechnique Fédérale de Lausanne .
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne .
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne .
    Polarization-resolved optical absorption in single V-groove quantum wires2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, p. 191111-Article in journal (Refereed)
    Abstract [en]

    Optical transitions associated with all three linear polarization directions were investigated in single GaAs V-groove quantum wires of different wire thicknesses. This was accomplished by combining absorption measurements in V-groove waveguide geometry with surface-excited photoluminescence excitation spectroscopy. The observed transitions were identified with the aid of model calculations. It is shown that excitonic intersubband coupling should be accounted for in order to explain the optical transitions associated with confined light-hole-like states. The results are relevant for the design of efficient quantum wire waveguide modulators and lasers.

  • 14.
    Palmgren, Susanna
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Schoenberg, A.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rudra, A.
    Dupertuis, M.-A.
    Leifer, K.
    Kapon, E.
    Optical absorption spectra in V-groove quantum wires: Experiment and theory2006In: Northern Optics,2006, 2006Conference paper (Other academic)
  • 15.
    Reichardt, H.
    et al.
    Ecole Polytechnique Fédérale de Lausanne.
    Leifer, K.
    Ecole Polytechnique Fédérale de Lausanne.
    Pelucchi, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne.
    Weman, Helge
    Ecole Polytechnique Fédérale de Lausanne.
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne.
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Influence of long-range substrate roughness on disorder in V-groove quantum wire structures2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, p. 123509-Article in journal (Refereed)
    Abstract [en]

    The observation and the interpretation of line splitting in photoluminescence and cathodoluminescence spectra of GaAs/AlGaAs V-groove quantum wires (QWRs) are reported. The QWR emission line splits into two peaks whose intensities oscillate systematically along the axis of the wire. Combining atomic force microscopy and cathodoluminescence measurements, we show a clear correlation between the surface topography of the V-groove and the individual peak intensities. We elucidate the relationship between the V-groove sidewall roughness and the shape at its bottom, and explain their impact on the QWR formation using a two-dimensional growth model accounting for self-limited growth in each V-groove domain. The influence of the long-range substrate roughness on the QWR spectral features is thus clarified. The study provides guidelines for improving QWR uniformity in order to achieve near-ideal model systems for one-dimensional semiconductors

  • 16. Sirigu, L.
    et al.
    Weman, Helge
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Oberli, D.Y.
    Rudra, A.
    Kapon, E.
    Optical emission from a V-groove quantum wire laser diode immersed in high magnetic fields2002In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 13, p. 881-Article in journal (Refereed)
  • 17.
    Weman, Helge
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Palmgren, Susanna
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kapon, E.
    Dasa, D.
    Fimland, B.-O.
    Semiconductor Quantum-Wires and Nano-Wires for optoelectronic Applications2007In: The International Conference on Optical, Optoelectronic and Photonic Materials and Applications ICOOPMA,2007, 2007Conference paper (Other academic)
  • 18.
    Weman, Helge
    et al.
    Norwegian University of Science and Technology .
    Palmgren, Susanna
    Ecole Polytechnique Fédérale de Lausanne.
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne.
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne.
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Dheeraj, D.L.
    Norwegian University of Science and Technology .
    Fimland, B.O.
    Norwegian University of Science and Technology .
    Harmand, J.C.
    CNRS.
    Semiconductor Quantum-Wires and Nano-Wires for optoelectronic Applications2009In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 20, no 1, p. S94-S101Article in journal (Refereed)
    Abstract [en]

    Exciton transfer between two parallel GaAs V-groove quantum wires (QWRs) or two planar quantum wells (QWs) separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence (PL) and PL excitation (PLE) spectroscopy. It is found that the transfer is strongly reduced between the widely spaced QWRs as compared with QWs. We have also investigated the optical absorption in single QWRs embedded in an AlGaAs V-shaped channel waveguide. Using a combination of PLE and absorption measurements we construct the full dependence of absorption spectra on the linear polarization. Our studies reveal the importance of inter-subband mixing in determining the energies of the light-hole-like transitions and thus the QWR absorption. Finally we present recent results on the fabrication and structural characterization of GaAs and GaP nanowires (NWs) grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates, using Au-catalyzed vapor–liquid–solid growth technique. It is shown that, apart from optimizing the NW growth parameters, substrate material and the procedure for preparing the substrate before the MBE growth play an important role in controlling the NWs.

  • 19.
    Weman, Helge
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Sirigu, L.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Leifer, K.
    Rudra, A.
    Kapon, E.
    High internal quantum efficiency, narrow linewidth emission InGaAs/GaAs/AlGaAs quantum wire light-emitting diode2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 15, p. 2839-2841Article in journal (Refereed)
    Abstract [en]

    High internal quantum efficiency (similar to60%), narrow linewidth (as narrow as 14 meV) exciton emission at room temperature has been obtained using strained InGaAs V-groove quantum wire (QWR) light-emitting diodes (LEDs). The high efficiency is achieved with the aid of selective carrier injection through self-ordered AlGaAs vertical quantum wells (VQWs), where the VQWs are separated from the InGaAs QWRs by thin GaAs spacer layers in order to reduce nonradiative recombination and inhomogeneous alloy broadening. Evidence for excitonic recombination in these LEDs up to RT is provided by measurements of the emission energy shifts at high magnetic fields.

  • 20.
    Weman, Helge
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Sirigu, L.
    Leifer, K.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rudra, A.
    Kapon, E.
    Efficient, narrow linewidth emission from InGaAs/AlGaAs V-groove quantum wire light-emitting diodes2002In: 14th Int. Conf. on Indium Phosphide and Related Materials IPRM 2002,2002, 2002Conference paper (Refereed)
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