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  • 101.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Unexpected behavior of InGaN quantum dot emission energy located at apices of hexagonal GaN pyramidsManuscript (preprint) (Other academic)
    Abstract [en]

    InGaN quantum dots (QDs) have been grown at the apices of hexagonal GaN pyramids. The pyramids were selectively grown on a (0001) oriented GaN template through circular apertures in a SiN mask positioned in square arrays. The emission of the InGaN QDs was shifted towards higher energies when the center-to-center distance of the pyramids was increased, while the emission from InGaN quantum wells located on the {1101} facets of the pyramids was energetically shifted towards lower energies. No energy shift was observed for (0001) truncated pyramids with truncation diameters larger than 100 nm.

  • 102.
    Lundskog, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 30, p. 305708-Article in journal (Refereed)
    Abstract [en]

    Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal–organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.

  • 103. 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)
  • 104.
    Malko, A.
    et al.
    Ecole Polytechnique Fédérale de Lausanne.
    Baier, M.H.
    Ecole Polytechnique Fédérale de Lausanne.
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne.
    Pelucchi, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Oberli, D.Y.
    Ecole Polytechnique Fédérale de Lausanne.
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Optimization of the efficiency of single-photon sources based on quantum dots under optical excitation2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, p. 081905-Article in journal (Refereed)
    Abstract [en]

    We demonstrate efficient, regulated single-photon operation from site-controlled InGaAs quantum dots (QDs) grown on a prepatterned substrate. Under nonresonant optical excitation, carriers trapped at structural or compositional defects of the adjacent nanostructures led to a degradation of the single-photon statistics from a QD. When the QD was excited quasiresonantly, single photons were emitted and a nearly complete suppression of multiphoton emission was achieved, making these QDs promising candidates for effective solid-state single-photon sources

  • 105.
    Malko, A.
    et al.
    Ecole Polytechnique Fédérale de Lausanne.
    Oberli, D.Y.
    Ecole Polytechnique Fédérale de Lausanne.
    Baier, M.H.
    Ecole Polytechnique Fédérale de Lausanne.
    Pelucchi, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Michelini, F.
    Ecole Polytechnique Fédérale de Lausanne.
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne.
    Dupertuis, M.-A.
    Ecole Polytechnique Fédérale de Lausanne.
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Single-photon emission from pyramidal quantum dots: The impact of hole thermalization on photon emission statistics2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, p. 195332-Article in journal (Refereed)
    Abstract [en]

    We report an experimental study of the emission statistics of excitonic complexes from a single quantum dot and their temperature dependence. The single photon emission from the exciton ground state is shown to persist up to 80  K. The deterioration of single photon statistics is attributed to new biexciton emissions, which emerge in the vicinity of the main single-exciton peak at rising temperatures. We identify these biexcitonic states as being formed by either one hole or two holes occupying excited states and analyze their specific polarization and power-dependent signature.

  • 106. Malko, A.
    et al.
    Oberli, D.Y.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Baier, M.H.
    Pelucchi, E.
    Michelini, F.
    Dupertuis, M.-A.
    Kapon, E.
    Biexcitonic excited states and multi-photon emission from single pyramidal quantum dots2006In: 4th International Conference on Quantum Dots,2006, 2006Conference paper (Other academic)
  • 107. 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)
  • 108. 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)
  • 109. Moskalenko, E.S.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Donchev, V
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Petroff, P.M.
    Effective optical manipulation of the charge state and emission intensity of the InAs/GaAs quantum dots by means of additional infrared illumination2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 5, p. 754-756Article in journal (Refereed)
    Abstract [en]

    The effect of infrared laser on charge state and emission intensity of the InAs/GaAs quantum dots (QDs)was analyzed. It was observed that the excitonic photoluminescence spectra of the QDs were redistributed in favor of the neutral excitation. It was also observed that photoluminescence intensity from the QDs increased by more than a factor of 5. The results showed that the emission intensity from the QDs can be effectively enhanced by optical means.

  • 110. Moskalenko, E.S.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Donchev, V.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Schoenfeld, W.V.
    Petroff, P.M.
    Exploitation of an Additional Infrared Laser to Modulate the Luminescence Intensity from InAs Quantum Dots2005In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 772, p. 705-706Article in journal (Refereed)
  • 111. Moskalenko, E.S.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Donchev, V
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology.
    Schoenfeld, W.V.
    Garcia, J.M.
    Petroff, P.M.
    The Effect of an Additional Infrared Excitation on the Collection Efficiency of InAs/GaAs Quantum Dots2004In: Virtual Journal of Nanoscale Science & Technology, ISSN 1553-9644, Vol. 7Article in journal (Refereed)
  • 112.
    Moskalenko, Evgenii
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Donchev, V.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Schoenfeld, W.V.
    Garcia, J.M.
    Petroff, M.
    Effect of an additional infrared excitation on the luminescence efficiency of a single InAs/GaAs quantum dot2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 15, p. 1553171-15531714Article in journal (Refereed)
    Abstract [en]

    Microphotoluminescence (PL) spectra of a single InAs/GaAs self-assembled quantum dot (QD) are studied under the main excitation of electron-hole pairs in the wetting layer (WL) and an additional infrared (IR) laser illumination. It is demonstrated that the IR laser with fixed photon energy well below the QD ground state induces striking changes in the spectra for a range of excitation energies and powers of the two lasers. For the main excitation above a threshold energy, defined as the onset of transitions between shallow acceptors and the conduction band in GaAs, the addition of the IR laser will induce a considerable increase in the QD emission intensity. This is explained in terms of additional generation of extra electrons and holes into the QD by the two lasers. For excitation below the threshold energy, the carrier capture efficiency from the WL into the QD is suggested to be essentially determined by the internal electric-field-driven carrier transport in the plane of the WL. The extra holes, generated in the GaAs by the IR laser, are supposed to effectively screen the built-in field, which results in a considerable reduction of the carrier collection efficiency into the QD and, consequently, a decrease of the QD PL intensity. A model is presented which allows estimating the magnitude of the built-in field as well as the dependence of the observed increase of the QD PL intensity on the powers of the two lasers. The use of an additional IR laser is considered to be helpful to effectively manipulate the emission efficiency of the quantum dot, which could be used in practice in quantum-dot-based optical switches.

  • 113.
    Moskalenko, Evgenii
    et al.
    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 .
    Donchev, V.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Petroff, M.
    The quenching effect of the light emission from individual InAs quantum dots initiated by an additional infra-red laser2004In: The Repino 2004 Conference,2004, 2004Conference paper (Other academic)
  • 114.
    Moskalenko, Evgenii
    et al.
    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 .
    Donchev, V.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Petroff, P.M.
    The effect of an additional infrared laser on the carrier collection efficiency of InAs quantum dots2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 24, p. 4896-4898Article in journal (Refereed)
    Abstract [en]

    The impact of single and multi-quantum dots (QD) on the exposure by a low-energy laser was investigated using micro-photoluminescence. The presence of the low-energy laser effectively quenched the single QD luminescence, at low temperatures. An induced screening of a built-in electric field that played an important role as a carrier capture mechanism led to this effect. When the capture efficieny was increased by elevated crystal temperature, the influence of the low-energy laser decreased.

  • 115.
    Moskalenko, Evgenii
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Donchev, V.T.
    Faculty of Physics, Sofia University, 5, Boulevard James Bourchier, 1164-Sofia, Bulgaria.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Schoenfeld, W.V.
    Materials Department, University of California, Santa Barbara, CA 93106.
    Petroff, P.M.
    Materials Department, University of California, Santa Barbara, CA 93106.
    Effects of separate carrier generation on the emission properties of InAs/GaAs quantum dots2005In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 5, no 11, p. 2117-2122Article in journal (Refereed)
    Abstract [en]

    Individual quantum dots have been studied by means of microphotoluminescence with dual-laser excitation. The additional infrared laser influences the dot charge configuration and increases the dot luminescence intensity. This is explained in terms of separate generation of excess electrons and holes into the dot from the two lasers. With increasing dot density and/or sample temperature, the increase of the luminescence intensity vanishes progressively, while the possibility to control the dot charge remains. © 2005 American Chemical Society.

  • 116.
    Moskalenko, Evgenii
    et al.
    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 .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Garcia, J.M.
    Petroff, P.M.
    Acceptor-induced threshold energy for the optical charging of InAs single quantum dots2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 19, p. 1953321-19533211Article in journal (Refereed)
    Abstract [en]

    We study the photoluminescence of single InAs/GaAs self-assembled quantum dots for a range of excitation powers, excitation energies and sample temperatures 4 K30 K), this effect vanishes due to the essential decrease of the steady-state free electron concentration in the GaAs barrier as a result of thermally excited free holes appearing in the GaAs barrier valence band which provides an effective recombination channel for the free electrons. These experimental observations could be used as an effective tool to create and study charged excitons in quantum dots.

  • 117.
    Moskalenko, Evgenii
    et al.
    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 .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Garcia, J.M.
    Petroff, P.M.
    Formation of the charged exciton complexes in self-assembled InAs single quantum dots2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, no 11, p. 6787-6793Article in journal (Refereed)
    Abstract [en]

    The low-temperature photoluminescence (PL) of the self-assembled InAs single quantum dots (QD) was studied using micro-PL setup. It was demonstrated that two emission lines down shifted in energy with respect to the ground state exciton PL line appeared in the PL spectrum. The PL intensity of these lines showed a periodic behavior with the excitation energy.

  • 118.
    Moskalenko, Evgenii
    et al.
    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, Semiconductor Materials.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Schoenfeld, W.V.
    Garcia, J.M.
    Petroff, P.M.
    Influence of excitation energy on charged exciton formation in self-assembled InAs single quantum dots2001In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 64, p. 085302-Article in journal (Refereed)
  • 119.
    Moskalenko, Evgenii
    et al.
    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 .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Garcia, J.M.
    Petroff, P.M.
    The formation of the charged exciton complexes in self-assembled InAs single quantum dots2001In: The 9th International Symposium on Nanostructures,2001, 2001, p. 558-Conference paper (Refereed)
  • 120.
    Moskalenko, Evgenii
    et al.
    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 .
    Schoenfeld, W.V.
    Petroff, P.M.
    The role of an external electric field for the carrier transport and capture into InAs/GaAs quantum dots2005In: The 23rd International Conference on Defects in Semiconductors,2005, 2005Conference paper (Other academic)
  • 121.
    Moskalenko, Evgenii
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, K.Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Donchev, V.
    Faculty of Physics, Sofia University, Sofia, 1164, Bulgaria.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Department of Materials, University of California, Santa Barbara, CA 93106, United States.
    Petroff, P.M.
    Department of Materials, University of California, Santa Barbara, CA 93106, United States.
    Effect of an electric field on the carrier collection efficiency of InAs quantum dots2005In: Physics of the solid state, ISSN 1063-7834, E-ISSN 1090-6460, Vol. 47, no 11, p. 2154-2161Article in journal (Refereed)
    Abstract [en]

    Individual and multiquantum dots of InAs are studied by means of microphotoluminescence in the case where, in addition to the principal laser exciting photoluminescence, second infrared laser is used. It is demonstrated that the absorption of the infrared photons effectively creates free holes in the sample, which leads to both a change in the charge state of a quantum dot and to a considerable reduction of their photoluminescence signal. The latter effect is explained in terms of effective screening of the internal electric field, facilitating carrier transport along the plane of a wetting layer, by the surplus holes from the infrared laser. It is shown that the effect of quenching of quantum dot photoluminescence gradually disappears at increased sample temperature (T) and/or dot density. This fact is due to the essentially increased value of quantum dot collection efficiency, which could be achieved at elevated sample temperatures for individual quantum dots or even at low T for the case of multiquantum dots. It is suggested that the observed phenomena can be widely used in practice to effectively manipulate the collection efficiency and the charge state of quantum-dot-based optical devices. © 2005 Pleiades Publishing, Inc.

  • 122.
    Moskalenko, Evgenii
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    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 .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Petroff, P.M.
    Enhancement of the luminescence intensity of InAs/GaAs quantum dots induced by an external electric field2007In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 7, no 1, p. 188-193Article in journal (Refereed)
    Abstract [en]

    InAs/GaAs quantum dots have been subjected to a lateral external electric field in low-temperature microphotoluminescence measurements. It is demonstrated that the dot PL signal could be increased several times depending on the magnitude of the external field and the strength of the internal (built-in) electric field, which could be altered by an additional infrared illumination of the sample. The observed effects are explained by a model that accounts for the essentially faster lateral transport of the photoexcited carriers achieved in an electric field. © 2007 American Chemical Society.

  • 123.
    Moskalenko, Evgenii
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Schoenfeld, W.V.
    Materials Department, University of California, Santa Barbara, United States.
    Petroff, P.M.
    Materials Department, University of California, Santa Barbara, United States.
    The effect of the external lateral electric field on the luminescence intensity of InAs/GaAs quantum dots2007In: Physics of the solid state, ISSN 1063-7834, E-ISSN 1090-6460, Vol. 49, no 10, p. 1995-1998Article in journal (Refereed)
    Abstract [en]

    We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications.

  • 124.
    Moskalenko, Evgeny
    et al.
    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 .
    Donchev, V.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Petroff, P.M.
    The considerable changes induced by an additional infrared laser on the luminescence intensity from InAs/GaAs quantum dots2004In: 27th International Conference on the Physics of Semiconductors ICPS-27,2004, 2004Conference paper (Other academic)
  • 125. Oberli, D.Y.
    et al.
    Byszewski, M.
    Chalupar, B.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rudra, A.
    Kapon, E.
    Tomography of the carrier gyromagnetic factors in quantum dots: observation of large anisotropies2008In: 29th International Conference on the Physics of Semiconductors ICPS,2008, 2008Conference paper (Other academic)
  • 126.
    Oberli, D.Y.
    et al.
    EPFL, Lausanne.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Dupertuis, M.A.
    EPFL, Lausanne.
    Pelucchi, E.
    Cork Univ. Ireland.
    Rudra, A.
    Cork Univ. Ireland.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kapon, E.
    EPFL Lausanne.
    Theory and detailed spectroscopy of high-symmetry quantum dots: Effects of symmetry elevation and breaking2010Conference paper (Refereed)
  • 127.
    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.

  • 128.
    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)
  • 129.
    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

  • 130.
    Shubina, Tatiana
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Jmerik, VN
    Ivanov, SV
    Kop'ev, PS
    Kavokin, A
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Narrow-line excitonic photoluminescence in GaN/AlxGa1-xN quantum well structures with inversion domains2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 24, p. 241306-Article in journal (Refereed)
    Abstract [en]

    Microphotoluminescence studies reveal strong and narrow lines of similar to1-meV minimal width in GaN/AlxGa1-xN quantum well (QW) structures having inversion domains (IDs). These narrow lines coexist in the spectra with broad (10-15 meV) peaks. The features of both kinds are characteristic for intersections of the IDs with QWs, which provide either three- or one-dimensional carrier confinement, depending on both the ID diameter and well width.

  • 131.
    Shubina, Tatiana
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Jmerik, VN
    Tkachman, MG
    Vekshin, VA
    Ratnikov, VV
    Toropov, AA
    Sitnikova, AA
    Ivanov, SV
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    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 .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Nanometric-scale fluctuations of intrinsic electric fields in GaN/AlGaN quantum wells with inversion domains2002In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 234, no 3, p. 919-923Article in journal (Refereed)
    Abstract [en]

    Strain and electric field fluctuations in regions of different polarities in GaN/AlGaN quantum well (QW) structures of dominant N-polarity with inversion domains (IDs) split the photoluminescence (PL) emission into two bands. Micro-PL and time-resolved PL studies reveal strong inhomogeneity of the array of the IDs, where essential parameters, such as strain, electric fields, and sizes are fluctuating quantities. We demonstrate also that the ID formation decreases the intrinsic electric field magnitudes.

  • 132.
    Shubina, Tatiana
    et al.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Jmerik, V.N.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Tkachman, M.G.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Vekshin, V.A.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Toropov, A.A.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Ivanov, S.V.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Kop'ev, P.S.
    Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St. Petersburg 194021, Russian Federation.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Optical properties of GaN/AlGaN quantum wells with inversion domains2003In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 195, no 3, p. 537-542Article in journal (Refereed)
    Abstract [en]

    Two-band photoluminescence (PL) and respective absorption and reflection features are observed in GaN/AlGaN MBE-grown quantum well (QW) structures of dominant N polarity with inversion domains (IDs). The PL bands are related to transitions in the regions of different polarity, characterized by different strain and electric fields. A micro-PL study reveals sharp and narrow (1.5-2.5 meV) PL lines placed between the bands, which are tentatively attributed to recombination at localization sites associated with intersections of the QWs with the domains. Additionally, we demonstrate that the ID formation decreases the overall strength of the intrinsic electric fields in the QW structures.

  • 133. Shubina, Tatiana
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Jmerik, V.N.
    Ivanov, S.V.
    Kavokin, P.S.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kopev, P.S.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Narrow-line excitonic luminescence in GaN/AlGaN nanostructures based on inversion domains2003In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 0, no 7, p. 2716-2720Article in journal (Refereed)
    Abstract [en]

    Presented at: 5th International Conference on Nitride Semiconductors (ICNS-5), Nara, Japan, 25-30 May, 2003 

  • 134. 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)
  • 135.
    Szeszko, J.
    et al.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures.
    Belykh, V. V.
    P. N. Lebedev Physical Institute, Russian Academy of Sciences.
    Gallo, P.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures.
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures.
    Karlsson, K Fredrik
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures.
    Sibeldin, N. N.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures.
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures.
    Exciton confinement and trapping dynamics in double-graded-bandgap quantum nanowires2012In: Applied Physics Letters, Vol. 100, no 21, article id 211907Article in journal (Refereed)
    Abstract [en]

    We fabricate and study quantum dot structures incorporating quasi-one-dimensional excited states. The structures are realized by graded bandgap GaAs/AlGaAs quantum wires self-formed inside inverted tetrahedral pyramids. The ground state transitions exhibit typical characteristics of fully confined excitons, including single photon emission. Efficient carrier thermalization and relaxation, as well as correlated photon emission is observed also among the excited states, indicating the formation of quasi-one-dimensional multi-exciton states. These structures offer interesting possibilities for collecting and directing charge carriers towards heterostructured potential traps.

  • 136.
    Togashi, Rie
    et al.
    Tokyo University of Agriculture and Technology, Japan.
    Yamamoto, Sho
    Tokyo University of Agriculture and Technology, Japan.
    Karlsson, Fredrik K.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Murakami, Hisashi
    Tokyo University of Agriculture and Technology, Japan.
    Kumagai, Yoshinao
    Tokyo University of Agriculture and Technology, Japan.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Koukitu, Akinori
    Tokyo University of Agriculture and Technology, Japan.
    Effect of High NH3 Input Partial Pressure on Hydride Vapor Phase Epitaxy of InN Using Nitrided (0001) Sapphire Substrates2013In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 52, no 8Article in journal (Refereed)
    Abstract [en]

    The influence of the source gas supply sequence prior to growth and the NH3 input partial pressure (PoNH3) on the nucleation of InN islands during the initial stages of hydride vapor phase epitaxy on a nitrided (0001) sapphire substrate was investigated. The crystalline quality of the InN layer after subsequent lateral growth was also examined. When NH3 was flowed prior to growth, single-crystal hexagonal InN islands formed. When InN was grown with a higher PoNH3, the number of InN islands decreased remarkably while their diameter increased. The crystalline quality of InN grown on the hexagonal islands with a high PoNH3 significantly improved with increasing growth time. A strong PL spectrum was observed only from InN layers grown with a high PoNH3. It was thus revealed that an NH3 preflow and a high PoNH3 are effective for producing InN with high crystalline quality and good optical and electrical properties.

  • 137. Toropov, A.A.
    et al.
    Nekrutina, O.V.
    Shubina, Tatiana
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ivanov, S.V.
    Gruber, Th.
    Kling, R.
    Reuss, F.
    Kirchner, C.
    Waag, A.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Excitonic Properties of ZnO Films and Nanorods2005In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 772, p. 991-992Article in journal (Refereed)
  • 138. Toropov, A.A.
    et al.
    Nekrutkina, O.V.
    Choubina, Tatiana
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Gruber, Th.
    Kirchner, C.
    Waag, A.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Temperature-dependent exciton polariton photoluminescence in ZnO films2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 16, p. 165205-Article in journal (Refereed)
    Abstract [en]

    The polarized photoluminescence (PL) in a (0001) oriented ZnO epitaxial film is studied in the temperature range 4.5-250 K. We report the evidence of exciton polariton emission between 50 and 130 K. In this range the PL of mixed polariton modes is detected in the geometry of an extraordinary beam, realized by the use of a large-aperture microobjective collecting light from the cleaved sample edge at different angles with respect to the. c axis. The elevated temperatures facilitate the polariton emission due to the thermal population of both A and B exciton branches and the enhanced polariton scattering into the photonlike mixed modes.

  • 139. Toropov, AA
    et al.
    Nekrutkina, OV
    Shubina, Tatiana
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Gruber, T
    Kirchner, C
    Waag, A
    Karlsson, K.Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Temperature-dependent polarized luminescence of exciton polaritons in a ZnO film2005In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 202, no 3, p. 392-395Article in journal (Refereed)
    Abstract [en]

    We report on the studies of linearly polarized photoluminescence (PL) in a (0001) oriented ZnO epitaxial film, grown by metal organic chemical vapor deposition on a GaN template. The emission of mixed longitudinal-transverse exciton polariton modes was observed up to 130 K that evidences polaritonic nature of the excitonic spectrum up to this elevated temperature.

  • 140. Troncale, V.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Byszewski, M.
    Pelucchi, E.
    Rudra, A.
    Oberli, D.
    Kapon, E.
    Ordered Semiconductor Single and Coupled Quantum Dot Structures grown on Inverted Pyramid Patterned Substrates2006In: SCOPES Seminar,2006, 2006Conference paper (Other academic)
  • 141.
    Troncale, V.
    et al.
    Ecole Polytech Fed Lausanne.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kapon, E.
    Ecole Polytech Fed Lausanne.
    Dynamic switching of hole character and single photon polarization using the quantum confined Stark effect in quantum dot-in-dot structures2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 28, p. 285202-Article in journal (Refereed)
    Abstract [en]

    The engineering of the three-dimensional (3D) heterostructure potential in GaAs/AlGaAs pyramidal quantum dot-in-dots (DiDs) provides control over the valence band symmetry and hence on the polarization of the emitted photons. We propose a technique for dynamic switching of hole character and photon polarization in DiDs by means of an applied electric field. The structural parameters required for producing this effect are discussed. Asymmetric DiDs are found to be particularly suitable for obtaining switching with fields smaller than 1 kV cm(-1). The proposed device enables generation of single photons with dynamic control on the photon polarization, with potential applications in quantum information technology.

  • 142. Troncale, V.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Malko, A.
    Pelucchi, E.
    Oberli, D.
    Michelini, F.
    Dupertuis, M.-A.
    Kapon, E.
    New excitonic states observed in semiconductor quantum dots using polarization resolved optical measurements2006In: 28th International Conference on the Physics of Semiconductors ICPS,2006, 2006Conference paper (Other academic)
    Abstract [en]

      

  • 143.
    Troncale, V.
    et al.
    Ecole Polytechnique Fédérale de Lausanne .
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne .
    Oberli, D.Y.
    Ecole Polytechnique Fédérale de Lausanne .
    Byszewski, M.
    Ecole Polytechnique Fédérale de Lausanne .
    Malko, A.
    Ecole Polytechnique Fédérale de Lausanne .
    Pelucchi, E.
    Ecole Polytechnique Fédérale de Lausanne .
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne .
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne .
    Excited excitonic states observed in semiconductor quantum dots using polarization resolved optical spectroscopy2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, p. 081703-Article in journal (Refereed)
    Abstract [en]

    We present results on the polarization-resolved photoluminescence emitted from InGaAs/AlGaAs single quantum dots (QDs) grown in inverted tetrahedral pyramids. The emitted light was detected for two mutually perpendicular linear polarization directions in the less conventional cleaved-edge geometry, in addition to the standard top-emission geometry. Whereas the in-plane linear polarization was isotropic, as a consequence of the high symmetry of the system, we found a strong polarization anisotropy of the edge-emitted light revealing QD states of predominantly heavy- or light-hole character. By temperature control of the charge state, several neutral and charged light-hole like exciton complexes were identified. In particular, a biexciton showing a twofold radiative recombination path, leading to two nearly perpendicularly polarized emission multiplets, was identified. These results are also of technological relevance for any design of optoelectronic QD-integrated devices

  • 144.
    Troncale, V.
    et al.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Pelucchi, E.
    Tyndall National Institute.
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne, Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Dwir, B.
    Ecole Polytechnique Fédérale de Lausanne.
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne.
    Valence band engineering and polarization switching in quantum dots grown in inverted pyramids2009In: 2nd IEEE LEOS Winter Topicals, WTM 2009, 2009, p. 102-103Conference paper (Other academic)
    Abstract [en]

    Control on the degree of valence band mixing is experimentally achieved in the particular GaAs/AlGaAs quantum Dot-in-Dot (DiD) structure. The effect is reflected by the tunable polarization of the emitted photons.

  • 145. Troncale, V.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pelucchi, E.
    Rudra, A.
    He, Z.
    Kapon, E.
    Control of Hole Character and Emission Polarization in Pyramidal Quantum Dot-in-Dot Semiconductor Heterostructures2007In: 10th International Conference on the Optics of Excitons in Confined Systems,2007, 2007Conference paper (Other academic)
  • 146.
    Troncale, V.
    et al.
    Ecole Polytechnique Fédérale de Lausanne .
    Karlsson, Fredrik
    Ecole Polytechnique Fédérale de Lausanne .
    Pelucchi, E.
    Ecole Polytechnique Fédérale de Lausanne .
    Rudra, A.
    Ecole Polytechnique Fédérale de Lausanne .
    Kapon, E.
    Ecole Polytechnique Fédérale de Lausanne .
    Control of valence band states in pyramidal quantum dot-in-dot semiconductor heterostructures2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 24Article in journal (Refereed)
    Abstract [en]

    The character of the hole states in a pyramidal GaAsAlGaAs quantum dot-in-dot (DiD) heterostructure is shown to be controllable by tailoring the confinement potential shape. The change in ground valence band state from heavy hole like to light hole like is demonstrated by side-view polarization resolved photoluminescence measurements. The experimental findings are supported by three-dimensional numerical model calculations. The results are applicable for polarization control in quantum dot photonic devices. © 2007 American Institute of Physics.

  • 147.
    Tzamalis, Georgios
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Lemaur, Vincent
    University Mons Hainaut.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Andersson, Mats
    Chalmers.
    Crispin, Xavier
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Cornil, Jerome
    University Mons Hainaut.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fluorescence light emission at 1 eV from a conjugated polymer2010In: CHEMICAL PHYSICS LETTERS, ISSN 0009-2614, Vol. 489, no 1-3, p. 92-95Article in journal (Refereed)
    Abstract [en]

    While polymer light-emitting diodes are currently finding commercial applications in displays and lighting, the development of low bandgap polymers emitting in the infrared has received much less attention in spite of potential applications for instance in the field of communication technologies. We report here a light emission at 1 eV from a low bandgap polymer made of an alternation of dialkoxy-phenylene units and a low bandgap monomer composed of an electron accepting 2-thia-1,3,5,8-tetraaza-cyclopenta[b]naphthalene group fenced with electron donating thiophene units. The electronic structure of the polymer chains has been characterized at a quantum-chemical level to shed light into the experimental results.

  • 148.
    Urgessa, Z. N.
    et al.
    Nelson Mandela Metropolitan University, South Africa.
    Botha, J. R.
    Nelson Mandela Metropolitan University, South Africa.
    Eriksson, Martin O.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Mbulanga, C. M.
    Nelson Mandela Metropolitan University, South Africa.
    Dobson, S. R.
    Nelson Mandela Metropolitan University, South Africa.
    Tankio Djiokap, S. R.
    Nelson Mandela Metropolitan University, South Africa.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Low temperature near band edge recombination dynamics in ZnO nanorods2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 12, p. 123506-Article in journal (Refereed)
    Abstract [en]

    The recombination dynamics of neutral donor bound excitons ((DX)-X-o: I-4, I-6/6a) and near band edge defect-related emission in solution grown ZnO nanorods are investigated using steady state and time-resolved photoluminescence (PL) measurements. The effects of annealing are also studied. Low temperature steady state PL shows a systematic removal of the I-4 line after annealing at 450 degrees C and the subsequent domination of I-6a in these PL spectra. Additionally, the time decay of the I-4, I-6/6a, free exciton (FX), and basal plane stacking fault-related (BSF) PL transitions are studied as a function of annealing temperature. For the various annealing temperatures studied, the PL decay is described by a bi-exponential profile with a fast component (contribution from the surface) and slow component (related to bulk recombination). The fast component dominates in the case of as-grown and low temperature annealed samples (anneal temperatures up to 300 degrees C), suggesting the presence of surface adsorbed impurities. For samples annealed above 400 degrees C, the effects of the surface are reduced. The sample annealed at 850 degrees C produced an overall enhancement of the crystal quality. The underlying mechanisms for the observed PL characteristics are discussed based on near surface band bending caused by surface impurities.

  • 149.
    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)
  • 150.
    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.

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