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  • 1. Arnaudov, B
    et al.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Evtimova, S
    Heuken, M
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hall effect data analysis of GaN n(+)n structures2002In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 234, no 3, p. 872-876Article in journal (Refereed)
    Abstract [en]

    We develop a model for analysis of Hall effect data of GaN structures composed of sublayers with different thicknesses and contacts placed on the top surface, We analysed the contributions of the conductivity of every sublayer of a planar sample taking into account the fact that the sample sublayers are partially connected in parallel to each other by series resistances formed in areas lying below the contacts from the upper layer. Correction factors, which reduce the contribution of the underlying layers to the measured whole sample conductivity, are obtained from the equations relevant to the respective equivalent circuit.

  • 2.
    Briones-Leon, Antonio
    et al.
    University of Vienna, Austria .
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Ayala, Paola
    University of Vienna, Austria .
    Kataura, Hiromichi
    National Institute Adv Ind Science and Technology, Japan .
    Yanagi, Kazuhiro
    Tokyo Metropolitan University, Japan .
    Weschke, Eugen
    Helmholtz Zentrum Berlin Fr Mat and Energie, Germany .
    Pichler, Thomas
    University of Vienna, Austria .
    Shiozawa, Hidetsugu
    University of Vienna, Austria .
    Orbital and spin magnetic moments of ferrocene encapsulated in metallicity sorted single-walled carbon nanotubes2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2424-2427Article in journal (Refereed)
    Abstract [en]

    The nature of the electronic and local magnetic properties of ferrocene (FeCp2) filled single-walled carbon nanotubes (SWCNT) has been investigated by X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Metallic, semiconducting, and unsorted ferrocene-filled tubes have been studied in different conditions of temperature and magnetic field. XMCD signal becomes evident with the application of a magnetic field at low temperature. We find that the molecular states of ferrocene interact with SWCNT of different metallicities. A paramagnetic behavior of encapsulated ferrocene is observed from the magnetic field dependent XMCD measurements which is consistent with theoretical predictions.

  • 3.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pozina, Galia
    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.
    Xin, H. P.
    Tu, C. W.
    Mechanism for Light Emission in GaNAs/GaAs Structures Grown by Molecular Beam Epitaxy1999In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 216, no 1, p. 125-129Article in journal (Refereed)
    Abstract [en]

     A detailed photoluminescence (PL) study reveals that the low-temperature PL emission in GaNAs epilayers and GaAs/GaNxAs1 - x quantum well structures grown by molecular beam epitaxy is governed by recombination of localized excitons. This conclusion is based on the analysis of the PL lineshape, its dependence on the excitation power and measurement temperature, as well as PL transient data. The depth of the localization potential is estimated as about 60 meV, varying slightly among the different structures.

  • 4.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Long delays of light in ZnO caused by exciton-polariton propagation2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 7, p. 1307-1311Article in journal (Refereed)
    Abstract [en]

    We study the propagation of exciton-polaritons through bulk ZnO using time-resolved photoluminescence (PL) complemented by time-of-flight measurements of laser pulses. When the photon energy approaches donor bound exciton resonances, substantial time delays in PL light propagation are observed which reach up to 210 ps for a 0.55 mm thick crystal. By comparing results from time-of-flight measurements performed using PL light and laser pulses, the observed delay is shown to be due to the formation of exciton-polaritons and their spectral dispersion. It is also shown that the main contribution to the slow-down effect arises from free exciton-polaritons, whereas bound exciton-polaritons become important only in close vicinity to the corresponding resonances.

  • 5.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Schubert, M
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Figge, S
    Hommel, D
    Haskell, BA
    Fini, PT
    Nakamura, S
    Assessment of phonon mode characteristics via infrared spectroscopic ellipsometry on a-plane GaN2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 7, p. 1594-1598Article in journal (Refereed)
    Abstract [en]

    Generalized infrared spectroscopic ellipsometry was applied to study the vibrational properties of anisotropically strained a-plane GaN films with different thicknesses. We have established a correlation between the phonon mode parameters and the strain, which allows the determination of the deformation potentials and strain-free frequency of the GaN A,(TO) mode. These results are compared with previous theoretical and experimental findings and discussed.

  • 6.
    Duc Tran, Thien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ohshima, Takeshi
    Japan Atomic Energy Agency, Takasaki, Japan.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Electronic properties of defects in high-fluence electron irradiated bulk GaN2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 253, no 3, p. 521-526Article in journal (Refereed)
    Abstract [en]

    Using deep level transient spectroscopy, deep levels and capture cross sections of defects introduced by high-fluence electron irradiation of thick halide vapour phase epitaxy grown GaN has been studied. After irradiation with 2 MeV electrons to a high-fluence of 5×1016 cm-2, four deep trap levels, labelled T1 (EC – 0.13 eV), T2 (EC – 0.18 eV), T3 (EC – 0.26 eV) T4 and a broad band of peaks consisting of at least two levels could be observed. These defects, except T1 and T3, were annealed out after annealing at 650 K for 2 hours. The capture cross section is found to be temperature independent for T2 and T3, while T1 shows an decresing capture cross section with increasing temperature, suggesting that electron capturing to this deep level is governed by a cascade capturing process.

  • 7.
    Hammerschmidt, T.
    et al.
    Ruhr University of Bochum, Germany .
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Alfe, D.
    UCL, England UCL, England .
    Fries, S. G.
    Ruhr University of Bochum, Germany .
    Hoglund, L.
    KTH Royal Institute Technology, Sweden .
    Jacobs, M. H. G.
    Technical University of Clausthal, Germany .
    Kossmann, J.
    Ruhr University of Bochum, Germany .
    Lu, X-G.
    Shanghai University, Peoples R China .
    Paul, G.
    ThyssenKrupp Steel Europe, Germany .
    Including the effects of pressure and stress in thermodynamic functions2014In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, no 1, p. 81-96Article in journal (Refereed)
    Abstract [en]

    Most applications of thermodynamic databases to materials design are limited to ambient pressure. The consideration of elastic contributions to thermodynamic stability is highly desirable but not straight-forward to realise. We present examples of existing physical models for pressure-dependent thermodynamic functions and discuss the requirements for future implementations given the existing results of experiments and first-principles calculations. We briefly summarize the calculation of elastic constants and point out examples of nonlinear variation with pressure, temperature and chemical composition that would need to be accounted for in thermodynamic databases. This is particularly the case if a system melts from different phases at different pressures. Similar relations exist between pressure and magnetism and hence set the need to also include magnetic effects in thermodynamic databases for finite pressure. We present examples to illustrate that the effect of magnetism on stability is strongly coupled to pressure, temperature, and external fields. As a further complication we discuss dynamical instabilities that may appear at finite pressure. While imaginary phonon frequencies may render a structure unstable and destroy a crystal lattice, the anharmonic effects may stabilize it again at finite temperature. Finally, we also outline a possible implementation scheme for strain effects in thermodynamic databases.

  • 8.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. 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 .
    Paskov, Plamen
    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 .
    Valcheva, E
    Iwaya, M
    Kamiyama, S
    Amano, H
    Akasaki, I
    Optical observation of discrete well width fluctuations in wide band gap III-nitride quantum wells2007In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, no 5, p. 1727-1734Article in journal (Refereed)
    Abstract [en]

    A detailed observation of discrete well width fluctuations via localized excitons in the photoluminescence (PL) spectra of MOCVD-grown undoped GaN/Al0.07Ga0.93 N multiple quantum wells (MQWs) has been reported. Doublet excitonic features with a distance varying between 10 and 25 meV for different well widths (1.5 to 4.5 nm) are observed in the PL spectra. They are explained in terms of discrete well width variations by one c-lattice parameter, i.e. two GaN monolayers. By mapping the PL measurements across the samples with different excitation spot size, it is shown that the extension of areas with a constant well width is less than 1 μm2. TEM pictures give evidence of interface roughness, although the contrast is weak at this low Al composition. In addition we observe a long-range variation of the PL peak position across the sample, interpreted as a fluctuation in Al composition in the barriers. The residual broadening of an excitonic peak (apart from the splitting related to well width fluctuations) is about 10 meV, somewhat larger for larger well widths, and is mainly ascribed to hole localisation potentials in the QWs. Additional broadening occurs in the MQWs due to inequivalent properties of each QW within the excitation spot. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

  • 9. Haratizadeh, H.
    et al.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    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 .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Iwaya, M.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Amano, H.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Akasaki, I.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Time resolved photoluminescence study of Si modulation doped GaN/Al 0.07Ga0.93N multiple quantum wells2004In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 241, no 5, p. 1124-1133Article in journal (Refereed)
    Abstract [en]

    The effects of the Si doping level on the recombination dynamics and carrier (exciton) localization in modulation doped GaN/Al0.07Ga 0.93N multiple-quantum-well (MQW) structures were studied by means of photoluminescence (PL) and time-resolved PL measurements. All samples with different doping levels show a QW emission which is blue shifted with respect to the 3.48 eV PL peak from the GaN buffer layer. The decay time at the peak position remains nearly constant in the range of 320-420 ps at 2 K for all doping levels. For the undoped and low-doped samples (3 × 1018 cm-3), which have less free electrons in the QWs, a non-exponential PL decay behaviour at 2 K is attributed to localized exciton recombination. The more highly doped samples (5 × 1018 cm-3 to 10 20 cm-3) show almost exponential decay curves at 2 K, suggesting the recombination of free electrons and localized holes. This localization effect appears even at high electron concentrations to cancel the expected lowering of the radiative lifetime with doping at 2 K, such a lowering is clearly observed at elevated temperatures for the highly doped samples, however. The internal polarization-induced fields of the medium and highly-doped samples are partly screened by the electrons originating from the doping in the barriers. Only the PL peak of the undoped and low-doped samples shows a redshift with time delay, related to the photogenerated carriers. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 10. Isoya, J.
    et al.
    Umeda, T.
    Mizuochi, N.
    Nguyen, Son Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ohshima, T.
    EPR identification of intrinsic defects in SiC2008In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 245, no 7, p. 1298-1314Article in journal (Refereed)
    Abstract [en]

    The structure determination of intrinsic defects in 4H-SiC, 6H-SiC, and 3C-SiC by means of EPR is based on measuring the angular dependence of the 29Si/13C hyperfine (HF) satellite lines, from which spin densities, sp-hybrid ratio, and p-orbital direction can be determined over major atoms comprising a defect. In most cases, not only the assignment of the variety due to the inequivalent sites (h- and k-sites in 4H-SiC) but also the identification of the defect species is accomplished through the comparison of the obtained HF parameters with those obtained from first principles calculations. Our works of identifying vacancy-related defects such as the monovacancies, divacancies, and antisite-vacancy pairs in 4H-SiC are reviewed. In addition, it is demonstrated that the observation of the central line of the TV2a center of S = 3/2 has been achieved by pulsed-ELDOR. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

  • 11.
    Jansson, Roger
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Zangooie, S
    Linkoping Univ, Dept Phys & Measurement Technol, Appl Phys Lab, SE-58183 Linkoping, Sweden.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology.
    Characterization of 3C-SiC by spectroscopic ellipsometry2000In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 218, no 1, p. R1-R2Article in journal (Refereed)
  • 12.
    Johansson, Leif I
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Reactions on the SiC(0001) root 3 x root 3 R30 degrees surface after Ti deposition and annealing2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 3, p. 667-673Article in journal (Refereed)
    Abstract [en]

    The interactions of thin Ti layers deposited on the SiC(0001) root 3 x root 3 R30 degrees surface at room temperature and after annealing at temperatures from 450 to 1200 degrees C was investigated using photoemission and LEED. Chemically shifted components were revealed in the Si 2p spectrum and found to be more intense and pronounced than the shifted component in the C 1s spectrum after Ti deposition and annealing. The relative intensity of these shifted components were found to increase initially upon annealing at temperatures up to around 700 degrees C. At temperatures above 800 degrees C only the shifted component in the C 1s spectrum remained which indicate that only TiC then remains on the surface. At annealing temperatures of 600-700 degrees C formation of the ternary Ti(3)SiC(2) phase and an interface TiSi(x) layer is suggested from shifts and relative intensities observed for these components. That the formation and decomposition of the ternary phase occurs at a considerably lower temperature than earlier reported is attributed to the fact that we investigated the interaction of considerably thinner Ti layers with SiC substrates than in those earlier reported studies.

  • 13.
    Kamata, N.
    et al.
    Saitama University, Japan.
    Suetsugu, M.
    Saitama University, Japan.
    Haque, D.
    Saitama University, Japan.
    Yagi, S.
    Saitama University, Japan.
    Yaguchi, H.
    Saitama University, Japan.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Spectral change of intermediate band luminescence in GaP:N due to below-gap excitation: Discrimination from thermal activation2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 2, article id UNSP 1600566Article in journal (Refereed)
    Abstract [en]

    As an intermediate band (IB) originating from discrete nitrogen (N) levels is formed in GaP:N with increasing N concentration, GaP1-xNx alloy is considered to be a promising candidate for IB-type solar cells. We studied the IB luminescence of a GaP1-xNx with 0.56% N and detected carrier recombination (CR) levels by superposing a below-gap excitation (BGE) light of 1.17eV. We resolved a high-energy component of 2.15eV in the IB luminescence, I-high, from total luminescence intensity I-all. With increasing the BGE density at fixed temperature of 5K, the amount of decrease in I-high was distinctly smaller than that of simple temperature rise without the BGE at the same I-all value. We conclude that the observed intensity change of the IB luminescence due to the BGE comes not from thermal activation, but from optical excitation among the IB, conduction band, and CR levels in GaP1-xNx. It is of primal importance to understand CR levels toward determining their origins and eliminating them for realization of efficient IB-type solar cells.

  • 14.
    Karpus, V.
    et al.
    Centre Phys Science and Technology, Lithuania.
    Tumenas, S.
    Centre Phys Science and Technology, Lithuania.
    Eikevicius, A.
    Centre Phys Science and Technology, Lithuania.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Interband optical transitions of Zn2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 253, no 3, p. 419-428Article in journal (Refereed)
    Abstract [en]

    Experimental results of an optical study of single-crystal zinc are presented. Components of the Zn dielectric function tensor were measured by spectroscopic ellipsometry in the 0.1-5 eV spectral range. In the NIR-VIS range, the dielectric function spectra show two clearly resolved, polarization-dependent optical features located at about 1 and 1.7 eV. The optical features were analyzed in a framework of parallel-band optical transitions. The performed theoretical calculations of the optical conductivity spectra well reproduce the experimental data with respect to positions, intensities, and polarization dependencies of the observed interband absorption peaks. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 15.
    Kharlamova, Marianna V.
    et al.
    University of Vienna, Austria Moscow MV Lomonosov State University, Russia .
    Sauer, Markus
    University of Vienna, Austria .
    Saito, Takeshi
    National Institute Adv Ind Science and Technology, Japan .
    Krause, Stefan
    BESSY II, Germany .
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Yanagi, Kazuhiro
    Tokyo Metropolitan University, Japan .
    Pichler, Thomas
    University of Vienna, Austria .
    Shiozawa, Hidetsugu
    University of Vienna, Austria .
    Inner tube growth properties and electronic structure of ferrocene-filled large diameter single-walled carbon nanotubes2013In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 250, no 12, p. 2575-2580Article in journal (Refereed)
    Abstract [en]

    We study the filling of single-walled carbon nanotubes (SW- CNTs) with ferrocene molecules. Using e-DIPS SWCNTs with a mean diameter of 1.7nm, we obtain a filling factor as high as 90%. At elevated temperatures in high vacuum the filled SWCNTs are transformed to double-walled carbon nanotubes (DWCNTs). Temperature dependence of inner tube growth is investigated by Raman spectroscopy. The electronic properties of the obtained nanostructures are studied by X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy. It is found that the growth temperature is higher for larger diameter inner tubes. It is demonstrated that ferrocene filling leads to electron doping of SWCNTs.

  • 16.
    Kordina, Olle
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hallin, Christer
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ellison, A.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Son, Nguyen Tien
    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.
    Growth of SiC by "Hot-Wall" CVD and HTCVD1997In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 202, no 1, p. 321-334Article in journal (Refereed)
    Abstract [en]

    A reactor concept for the growth of high-quality epitaxial SiC films has been investigated. The reactor concept is based on a hot-wall type susceptor which, due to the unique design, is very power efficient. Four different susceptors are discussed in terms of quality and uniformity of the grown material. The films are grown using the silane–propane–hydrogen system on off-axis (0001) 6H- and 4H-SiC substrates. Layers with doping levels in the low 1014 cm—3 showing strong free exciton emission in the photoluminescence spectra may readily be grown reproducibly in this system. The quality of the grown layers is also confirmed by the room temperature minority carrier lifetimes in the microsecond range and the optically detected cyclotron resonance data which give mobilities in excess of 100000 cm2/Vs at 6 K. Finally, a brief description will be given of the HTCVD technique which shows promising results in terms of high quality material grown at high growth rates.

  • 17.
    Kuzmany, H.
    et al.
    University of Vienna, Austria.
    Shi, L.
    University of Vienna, Austria.
    Pichler, T.
    University of Vienna, Austria.
    Kramberger, C.
    University of Vienna, Austria.
    Chernov, A.
    RAS, Russia.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Nondispersive Raman lines in the D-band region for ferrocene functionalized carbon nanotubes2014In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, no 12, p. 2457-2460Article in journal (Refereed)
    Abstract [en]

    Carbon-rich fillers like ferrocene can be transformed into an inner tube with extremely small diameter if they are filled into HiPco tubes. For ferrocene@HiPco three new Raman bands appear in the D-band region during this transformation. These bands do not show dispersion and exhibit a strong resonance for red laser excitation. The observed resonance is for the outgoing phonon at 1247 cm(-1) for an electronic transition at 1.84 eV. Maximum response for the new lines is observed for transformation of the filled tubes between 800 and 900 degrees C. In addition to the three bands in the D-band region also an enhanced band at 470 cm(-1) is observed with the same sensitivity to transformation temperature. In order to obtain more information on the origin of the new bands deuterium substituted FeCp2 was used. The new lines turned out to be sensitive to this substitution which is considered as a strong indication of their origin from organic compounds created inside or in between the tubes during the transformation process.

  • 18.
    Lilja, Louise
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    In-grown stacking-faults in 4H-SiC epilayers grown on 2 degrees off-cut substrates2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 6, p. 1319-1324Article in journal (Refereed)
    Abstract [en]

    4H-SiC epilayers were grown on 2 degrees off-cut substrates using standard silane/propane chemistry, with the aim of characterizing in-grown stacking faults. The stacking faults were analyzed with low temperature photoluminescence spectroscopy, room temperature photoluminescence mappings, room temperature cathodoluminescence and synchrotron white beam X-ray topography. At least three different types of in-grown stacking faults were observed, including double Shockley stacking faults, triple Shockley stacking faults and bar-shaped stacking faults. Those stacking faults are all previously found in 4 degrees and 8 degrees off-cut epilayers; however, the geometrical size is larger in epilayers grown on 2 degrees off-cut substrates due to lower off-cut angle. The stacking faults were formed close to the epilayer/substrate interface during the epitaxial growth. (C) 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

  • 19.
    Lorenz, K
    et al.
    Instituto Tecnolo´ gico e Nuclear, Estrada Nacional 10, 2696-953 Sacave´m, Portugal and Centro de Fı´ sica Nuclear da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal.
    Magalhaes, S
    Instituto Tecnolo´ gico e Nuclear, Estrada Nacional 10, 2696-953 Sacave´m, Portugal and CICECO, Departamento de Fı´ sica and I3N, Universidade de Aveiro, 3810-193 Aveiro, Portuga.
    Franco, N
    Instituto Tecnolo´ gico e Nuclear, Estrada Nacional 10, 2696-953 Sacave´m, Portugal and Centro de Fı´ sica Nuclear da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal.
    Barradas, N. P.
    Instituto Tecnolo´ gico e Nuclear, Estrada Nacional 10, 2696-953 Sacave´m, Portugal and Centro de Fı´ sica Nuclear da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Alves, E
    Instituto Tecnolo´ gico e Nuclear, Estrada Nacional 10, 2696-953 Sacave´m, Portugal and Centro de Fı´ sica Nuclear da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal.
    Pereira, S
    CICECO, Departamento de Fı´ sica and I3N, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
    Correia, M. R.
    CICECO, Departamento de Fı´ sica and I3N, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
    Munnik, F
    Forschungszentrum Dresden Rossendorf, 01314 Dresden, Germany.
    Martin, R. W.
    Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK.
    O´Donnell, K. P.
    Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK.
    Watson, I. M.
    Institute of Photonics, SUPA, University of Strathclyde, Glasgow G4 0NW, UK.
    Al1xInxN/GaN bilayers: Structure,morphology, and optical properties2010In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 247, no 7, p. 1740-1746Article in journal (Refereed)
    Abstract [en]

    High quality Al1xInxN/GaN bilayers, grown by metal organic chemical vapor deposition (MOCVD), were characterized using structural and optical techniques. Compositional analysis was performed using Rutherford backscattering spectrometry(RBS) and elastic recoil detection analysis (ERDA). The InN molar fraction x decreased approximately linearly with increasing growth temperature and ranged from x¼0.13 to0.24. Up tox¼0.20 the layers grow pseudomorphically to GaN with good crystalline quality. These layers show a smoothsurface with V-shaped pits. Two layers with InN contents around 24% showed partial strain relaxation. However, themechanisms leading to relaxation of compressive strain arevery different in the two samples grown both at similartemperature but with different growth rates. One sample shows a decreased c/a ratio, as expected for relaxation of the compressive strain, while In was shown to be homogeneouslydistributed with depth. The other sample started to grow withx¼0.24 but relaxed mainly by reduction of the incorporated InN content towards the lattice-match composition of x0.17. Both samples have an increased surface roughness. All samples show strong Al1xInxN band edge luminescence with large bowing parameter and Stokes’ shifts.

  • 20. Malinauskas, T
    et al.
    Jarasiunas, K
    Aleksiejunas, R
    Gogova, Daniela
    Linköping University, The Institute of Technology. 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 .
    Beaumont, B
    Gibart, P
    Contribution of dislocations to carrier recombination and transport in highly excited ELO and HYPE GaN layers2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 7, p. 1426-1430Article in journal (Refereed)
    Abstract [en]

    Nonequilibrium carrier dynamics has been investigated in ELO and HYPE grown GaN layers in a wide temperature and excitation range by using the time-resolved picosecond FWM technique. Carrier lifetime in the samples at 300 K increased up to 2.8-5.1 ns in accordance with the decreasing threading dislocation density from 4 x 10(7) cm(-2) (ELO) to mid 106 cm(-2) in HYPE layers. At T < 100 K, the hyperbolic shape of FWM kinetics indicated carrier density dependent radiative lifetimes, which gradually decreased at lower temperatures to a few hundreds of ps. The dominance of bimolecular recombination in HVPE layers at 10-40 K was demonstrated by the exposure characteristic of FWM, that has shown a sublinear growth of carrier density with excitation, N proportional to I-1/2. Numerical fitting of the set of FWM kinetics at various T confirmed the temperature dependence of bimolecular recombination coefficient B proportional to T-1/5 and provided its value B = 2 x 10(-11) cm(3)/s at 300 K and 3.2 x 10(-9) cm(3)/s at 9 K. The measured bipolar diffusion coefficients allowed determination of carrier diffusion length of 0.8-1 mu m at 300 K and its dependence on dislocation density and temperature. (c) WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 21.
    Malysheva, Liubov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Onipko, A.
    Tunneling through molecular wires: A comparison of the Franz two-band model with exact results2007In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, no 11, p. 4244-4247Article in journal (Refereed)
    Abstract [en]

    This report concerns finding the tunneling exponential factor exp [-2 kappa(E) d], on the basis of electronic band structure of organic oligomers, which are d-long molecular wires. It is shown that energy dependence kappa(E) given by the Franz two-band model agrees remarkably well with exact model calculations, provided that the quadratic dispersion parameter is calculated from the real (non-parabolic) band structure of organic oligomers. For narrow and moderate band gaps (with respect to the band width), the approximate dependence is practically indistinguishable from that which is obtained from these exact calculations. The divergence (particularly, in the mid of the band gap) becomes appreciable and increases with an increase of the band-gap/band-width ratio. The apparent effective mass (as it is estimated from kappa(E) measured at the Fermi energy E=E-F) is defined in terms of the inherent parameters of the wire. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 22.
    Malysheva, Liubov
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Onipko, Alexander
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Coherent transmission in multiterminal molecular conductors2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 11, p. 2676-2679Article in journal (Refereed)
    Abstract [en]

    We consider coherent transport in an arbitrary molecular complex functioning as N-terminal conductor. The matrices that enter Dattas trace formula for the transmission function T(E) are represented in terms of free-molecule Greens function matrix elements referring exclusively to molecular atoms perturbed by the lead-molecule interaction. Explicit expressions of transmission function are obtained for a commonly used model of multiterminal molecular devices, where the molecule is coupled with each lead via a single bond. In the particular cases of connection of molecular wires via a single atom and a benzene ring, this gives the analytical expressions of T(E). Physical implications of the derived formulas are briefly discussed.

  • 23.
    Malysheva, Lyuba
    et al.
    Bogolyubov Inst fo Theoretical Physics, 03143 Kiev. Ukraine.
    Onipko, Alexander
    Div och Molecular Physics Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping Sweden.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Orientation of OH terminal groups in oligo(ethylene glycol)-terminated self-assemblies: results of ab initio modeling2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 13, p. 3489-3493Article in journal (Refereed)
    Abstract [en]

       

  • 24.
    Malysheva, Lyuba
    et al.
    Bogolyubov Inst Theoret Phys, UA-03680 Kiev, Ukraine.
    Petrenko, Evgenij
    Natl Taras Shevchenko Univ Kyiv, UA-03022 Kiev, Ukraine.
    Onipko, Alexander
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Interband transmission in armchair graphene ribbons with a step-like profile of potential energy: Relevance to Kleins tunneling2009In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 246, no 11-12, p. 2549-2552Article in journal (Refereed)
    Abstract [en]

    Three principal results concerning graphene-based wires and their ambipolar behavior are presented. First, it is the exact expression of the transmission coefficient for armchair graphene wires described by the tight-binding Hamiltonian with the step-like change U of site energies. Second, the exact relation between the energy of incident electrons or holes and potential U at which there is no backscattering for the given mode of the transverse motion. Third, the range of relevance of Kleins formula describing the motion of relativistic particles in the same potential profile is established. Analysis of newly derived results shows that physics of interband transitions at constant energy in graphene wires is richer than it was believed.

  • 25.
    Monemar, Bo
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    The 3.466 eV Bound Exciton in GaN2001In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, no 2, p. 489-492Article in journal (Refereed)
    Abstract [en]

     We discuss the available optical data for the 3.466 eV bound exciton in GaN, which has been a controversial issue in the recent literature. We conclude that the experimental results are only consistent with the identification as an exciton bound at a neutral acceptor with a spin-like bound hole. The chemical identity is still not clear.

  • 26.
    Monemar, Bo
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Harati Zadeh, Hamid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    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 .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    Influence of polarization fields and depletion fields on photoluminescence of AlGaN/GaN multiple quantum well structures2003In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 237, no 1, p. 353-364Article in journal (Refereed)
    Abstract [en]

    We report on a detailed study of low temperature photoluminescence (PL) in Al0.07Ga0.93N/GaN multiple quantum wells (MQWs). The structures were grown on sapphire with the conventional low temperature AlN nucleation layer and thick GaN buffer layer. Several sets of 5 QW MQW samples were studied, one set with Si doping in the barriers up to or above the metallic limit. Nominally undoped MQW samples were also studied. The spectral behaviour of the doped samples was strongly affected by the near surface depletion field, causing overlap of different spectra from non-equivalent QWs. The QWs closest to the surface are presumably inactive in some samples, due to a very high depletion field. For the case of undoped samples, on the other hand, the near surface QWs are active and most prominent in the PL spectra. The structure from discrete well width variations is here resolved in the PL spectra. The results demonstrate that for structures with no additional capping layer both the depletion field and the polarisation fields need to be considered in the interpretation of experimental data. The theoretically estimated fields in this work are consistent with the experimental spectra. The presence of localisation even in the case of metallic samples, as observed by a constant PL decay time independent of doping, is discussed in terms of penetration of the hole wave functions into the AlGaN barriers. This localisation is also manifested in a sizeable LO phonon coupling strength in all samples studied.

  • 27.
    Monemar, Bo
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Figge, S
    Dennemarck, J
    Hommel, D
    The dominant shallow 0.225 eV acceptor in GaN2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 7, p. 1604-1608Article in journal (Refereed)
    Abstract [en]

    We have studied the optical signatures of the Mg acceptor in GaN, using samples that are doped with Mg during MOCVD growth. In order to reduce the defect density in the material and thus achieve narrow linewidths in optical spectra we have used thick HVPE grown GaN layers as templates in the MOCVD growth. The photoluminescence (PL) spectra show two acceptor-related bound exciton peaks at 3.466 eV and 3.455 eV respectively. In the lower photon energy range the 3.27 eV emission with its LO-phonon replicas is dominant, riding on a broad background emission peaking at about 3.1 eV. These results, together with previous data in the literature, indicate that there are two acceptors in Mg-doped GaN, one dominating the optical spectra (the 3.466 eV and the 3.27 eV emissions) and another related to the 3.455 eV and the 3.1 eV emissions. We suggest that the latter is related to the Mg acceptor, while the former is a H-related complex, not necessarily involving Mg.

  • 28.
    Monemar, Bo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Toropov, A.A.
    Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021, Russian Federation.
    Shubina, T.V.
    Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021, Russian Federation.
    Recent developments in the III-nitride materials2007In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, no 6, p. 1759-1768Article in journal (Refereed)
    Abstract [en]

    We review a selection of recent research work on III-nitride materials, limiting the scope to bulk properties and quantum well structures. The different stages of development of the compounds AlN, GaN and InN are illustrated, with reference to the electronic properties demonstrated so far. The important alloy systems AlxGa1-xN and InxGa1-x have quite different properties, still not understood in detail for high Al and In contents, respectively. Some important unresolved issues are highlighted, and possible future directions of the materials development are indicated. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

  • 29.
    Monemar, Bo
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Toropov, A.A.
    Shubina, T.V.
    Malinauskas, T.
    Usui, A.
    Recombination of free and bound excitons in GaN2008In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 245, no 9, p. 1723-1740Article in journal (Refereed)
    Abstract [en]

    We report on recent optical investigations of free and bound exciton properties in bulk GaN. In order to obtain reliable data it is important to use low defect density samples of low doping. We have used thick GaN layers (of the order of 1 mm) grown by halide vapour phase epitaxy (HVPE) with a residual doping down to <1016 cm-3 in this work. With such samples all polarisation geometries could also easily be exploited. The influence of the surface states on the photoluminescence (PL) experiments is analysed, it is concluded that surface recombination plays an important role for the free exciton (FE) recombination. The electronic structure of the FEs is discussed in detail, including the influence of spin-exchange and polariton effects, and compared with polarised PL spectra at 2 K. The detailed structure of excited states from the PL spectra is discussed, but further data are needed to fully explain all the peaks observed. The polarized FE spectra at room temperature allow a determination of the bandgap as 3.437 eV at 290 K, assuming an exciton binding energy of 25 meV. The PL transient of the A FE is very short (about 100 ps) for the no-phonon (NP) line interpreted as dominated by nonradiative surface recombination. The longitudinal-optical (LO) phonon replicas of the A FE exhibit a longer decay of about 1.4 ns at 2 K, suggested to represent the bulk lifetime of the FE. The corresponding decay time at 290 K is 9 ns in our samples, a value that might be affected by nonradiative recombination. The Si and O donor bound exciton (DBE) spectra with sharp NP lines at 3.4723 eV and 3.4714 eV respectively, are well resolved together with the so-called two-electron transitions (TETs) and several optical phonon replicas. The electronic structure of the DBE states including excited rotational states is discussed and compared with experiment. The well-resolved TET lines allow an accurate determination of the ground state binding energy of the Si donor as 30.4 meV and 33.2 meV for the O donor. The PL transients of the DBEs reveal a non-exponential decay for the NP lines. The DBE NP transient lineshape is assumed to be influenced by optical dispersion and scattering in the vicinity of exciton resonances, as well as by surface effects. The DBE decay time can most properly be deduced from the PL decay of the respective TETs and LO replicas, leading to values in the range of 1.1-1.8 ns. These values differ significantly from previous theoretical predictions, where values about two orders of magnitude shorter were obtained. A tentative discussion of the main observed features of acceptor bound excitons (ABEs), which are much less studied in GaN, is given. A decay time of about 0.9 ns for the shallowest 3.466 eV ABE is estimated, i.e. shorter than that for the shallow donor BEs. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

  • 30.
    Monemar, Bo
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Hi Tech Res Ctr, Dept Mat Sci & Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Iwaya, M
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Hi Tech Res Ctr, Dept Mat Sci & Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Nitta, S
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Hi Tech Res Ctr, Dept Mat Sci & Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Amano, H
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Hi Tech Res Ctr, Dept Mat Sci & Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Akasaki, I
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Hi Tech Res Ctr, Dept Mat Sci & Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Optical characterization of InGaN/GaN MQW structures without in phase separation2001In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, no 1, p. 157-160Article in journal (Refereed)
    Abstract [en]

    Photoluminescence and cathodoluminescence spectroscopies are used to investigate the properties of the band edge emission of InGaN/(In)GaN multiple quantum well (MQW) structures which do not show evidence of phase separation in high resolution electron microscopy. The data still show a clear low energy peak in the spectra. about 0.1 eV below the main exciton peak. Possible interpretations of this second peak are discussed.

  • 31.
    Nilsson, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Trinh, Xuan Thang
    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.
    Son, Tien Nguyen
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    On the behavior of the silicon donor in conductive AlxGa1-xN (0.63≤x≤1) layers2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 6, p. 1306-1310Article in journal (Refereed)
    Abstract [en]

    We have studied the silicon donor behavior in intentionally silicon doped AlxGa1-xN (0.63≤x≤1) grown by hot-wall metal-organic chemical vapor deposition. Efficient silicon doping was obtained for lower Al contents whereas the conductivity drastically reduces for AlGaN layers with Al content in the range x~0.84-1. Degradation of the structural quality and compensation by residual O and C impurities were ruled out as possible explanations for the reduced conductivity. By combining frequency dependent capacitance-voltage and electron paramagnetic resonance measurements we show that the Si donors are electrically active and that the reduced conductivity can be explained by the increased activation energy caused by the sharp deepening of the Si DX state..

  • 32.
    Olovsson, Weine
    et al.
    Kyoto University, Sakyo Kyoto.
    Asker, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Core-level shifts in complex metallic systems from first principle2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 11, p. 2447-2464Article in journal (Refereed)
    Abstract [en]

    We show that core-level binding energy shifts (CLS) can be reliably calculated within density functional theory. The scheme includes both the initial (electron energy eigenvalue) as well as final state (relaxation due to core-hole screening) effects in the same framework. The results include CLS as a function of composition in substitutional random bulk and surface alloys. Sensitivity of the CLS to the local chemical environment in the bulk and at the surface is demonstrated. A possibility to use the CLS for structural determination is discussed. Finally, an extension of the model is made for Auger kinetic energy shift calculations.

  • 33.
    Palumbo, M.
    et al.
    Ruhr University of Bochum, Germany .
    Burton, B.
    NIST, MD 20899 USA .
    Costa e Silva, A.
    EEIMVR UFF, Brazil .
    Fultz, B.
    CALTECH, CA 91125 USA .
    Grabowski, B.
    Max Planck Institute Eisenforsch GmbH, Germany .
    Grimvall, G.
    KTH Royal Institute Technology, Sweden .
    Hallstedt, B.
    Rhein Westfal TH Aachen, Germany .
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Lindahl, B.
    KTH Royal Institute Technology, Sweden .
    Schneider, A.
    Vallourec Deutschland GmbH, Germany .
    Turchi, P. E. A.
    Lawrence Livermore National Lab, CA USA .
    Xiong, W.
    University of Wisconsin, WI 53706 USA .
    Thermodynamic modelling of crystalline unary phases2014In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, no 1, p. 14-32Article in journal (Refereed)
    Abstract [en]

    Progress in materials science through thermodynamic modelling may rest crucially on access to a database, such as that developed by Scientific Group Thermodata Europe (SGTE) around 1990. It gives the Gibbs energy G(T) of the elements in the form of series as a function of temperature, i.e. essentially a curve fitting to experimental data. In the light of progress in theoretical understanding and first-principles calculation methods, the possibility for an improved database description of the thermodynamics of the elements has become evident. It is the purpose of this paper to provide a framework for such work. Lattice vibrations, which usually give the major contribution to G(T), are treated in some detail with a discussion of neutron scattering studies of anharmonicity in aluminium, first-principles calculations including ab initio molecular dynamics (AIMD), and the strength and weakness of analytic model representations of data. Similarly, electronic contributions to G(T) are treated on the basis of the density of states N(E) for metals, with emphasis on effects at high T. Further, we consider G(T) below 300K, which is not covered by SGTE. Other parts in the paper discuss metastable and dynamically unstable lattices, G(T) in the region of superheated solids and the requirement on a database in the calculation of phase diagrams. (C) 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

  • 34.
    Paskov, Plamen
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Darakchieva, Vanya
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    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.
    Anisotropy of the in-plane strain in GaN grown on A-plane sapphire2002In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 234, no 3, p. 892-896Article in journal (Refereed)
    Abstract [en]

    A comparative study of GaN layer grown by hydride vapour phase epitaxy on A-plane sapphire before and after removal of the substrate is presented. A large anisotropy of the in-plane strain in the as-grown sample is revealed by X-ray diffraction measurements and polarized photoluminescence. The strain anisotropy is found to modify the selection rules for the transitions leading to a splitting of the optically active states of the A and B excitons. Almost complete strain relaxation and recovery of the optical isotropy in the (0001) plane is observed in the free-standing layer.

  • 35.
    Paskov, Plamen
    et al.
    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 .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    Phonon-assisted photoluminescence in InGaN/GaN multiple quantum wells2002In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 234, no 3, p. 755-758Article in journal (Refereed)
    Abstract [en]

    The LO-phonon sidebands of the photoluminescence in InGaN/GaN multiple quantum wells has been investigated in the temperature range from 20 to 300 K. Analysing the intensity distribution among the phonon replicas, the strength of the exciton-phonon interaction has been estimated. The Huang-Rhys factor was found to be ÿ0.3, much larger than in GaN. The enhancement has been attributed to the exciton localization on a length scale smaller than the exciton Bohr radius and to the large internal electric field, which increases the spatial separation of the electron and hole charge densities along the growth axis.

  • 36.
    Paskov, Plamen
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    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 .
    Internal structure of free excitons in GaN2001In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, no 2, p. 467-470Article in journal (Refereed)
    Abstract [en]

    Polarized photoluminescence is used to study the fine structure of free excitons in thick GaN layers grown on differently oriented sapphire substrates. The singlet-triplet splitting of the A exciton is measured and the exchange interaction constant in GaN is determined. For the samples grown on the a-plane sapphire, splitting of the A and B excitons induced by the uniaxial in-plane stress is also observed.

  • 37.
    Paskova, Tanja
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Darakchieva, Vanya
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Valcheva, E.
    Paskov, Plamen
    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 .
    Heuken, M.
    Aixtron AG, 52072 Aachen, Germany.
    Growth of GaN on a-plane sapphire: In-plane epitaxial relationships and lattice parameters2003In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 240, no 2, p. 318-321Conference paper (Other academic)
    Abstract [en]

    We have studied GaN films grown on a-plane sapphire substrates by both hydride vapor phase epitaxy (HVPE) and metalorganic vapor phase epitaxy (MOVPE). The in-plane orientation relationships between the epitaxial films and the substrate are determined to be [11-20]GaN ? [0001] sapphire and [1-100]GaN ? [1-100]sapphire in the HVPE growth, while [1-100]GaN ? [0001]sapphire and [11-20]GaN ? [1-100]sapphire are found in the MOVPE growth. The different orientation preferences are attributed to the atom termination of the sapphire surface determined by the substrate treatment used in the different growth methods. The effect of the lattice matches on the in-plane lattice parameters and strain anisotropy in the two cases is studied. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 38.
    Pozina, Galia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Univ Calif Santa Barbara, Mat & ECE Dept, Santa Barbara, CA 93106 USA.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Heying, B
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Univ Calif Santa Barbara, Mat & ECE Dept, Santa Barbara, CA 93106 USA.
    Speck, JS
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Univ Calif Santa Barbara, Mat & ECE Dept, Santa Barbara, CA 93106 USA.
    Radiative and nonradiative exciton lifetimes in GaN grown by molecular beam epitaxy2001In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, no 2, p. 485-488Article in journal (Refereed)
    Abstract [en]

    GaN epilayers grown by molecular-beam epitaxy (MBE) have been studied by temperature dependent time-resolved photoluminescence (PL). The PL decay times for free excitons and donor-bound excitons as well as the quantum efficiency have been measured for different temperatures. Radiative and nonradiative lifetimes have been evaluated from experimental values for the quantum efficiency and the PL decay time, assuming fully radiative processes at 2 K. The so obtained temperature dependence for the radiative lifetime cannot be described by a simple T-3/2 law for the whole temperature range. The temperature behavior of radiative lifetimes suggests the presence of a strong nonradiative recombination channel even at very low temperatures.

  • 39.
    Pozina, Galia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kaliteevski, Mikhail A.
    St Petersburg Academic University, Russia; Russian Academic Science, Russia; ITMO University, Russia.
    Nikitina, Ekaterina V.
    St Petersburg Academic University, Russia; Russian Academic Science, Russia.
    Denisov, Dmitrii V.
    St Petersburg Academic University, Russia; Russian Academic Science, Russia.
    Polyakov, Nikolai K.
    St Petersburg Academic University, Russia.
    Pirogov, Evgenii V.
    St Petersburg Academic University, Russia.
    Goray, Leonid I.
    St Petersburg Academic University, Russia; ITMO University, Russia; Institute Analyt Instrumentat, Russia.
    Gubaydullin, Azat R.
    St Petersburg Academic University, Russia; ITMO University, Russia.
    Ivanov, Konstantin A.
    ITMO University, Russia.
    Kaliteevskaya, Natalia A.
    St Petersburg Academic University, Russia; ITMO University, Russia; University of Durham, England.
    Egorov, Anton Yu.
    Russian Academic Science, Russia; ITMO University, Russia.
    Nonlinear behavior of the emission in the periodic structure of InAs monolayers embedded in a GaAs matrix2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 4, article id UNSP 1600402Article in journal (Refereed)
    Abstract [en]

    We report time-resolved photoluminescence (TRPL) measurements performed at different temperatures for the Bragg structure containing 60 InAs monolayer-based quantum wells (QWs) periodically arranged in a GaAs matrix. TRPL data reveal an appearance of the additional superradiant (SR) mode originated from coherent collective interaction of QWs. The SR mode is not manifested in the case if a small number of QWs is excited, then only an exciton emission related to the InAs QWs dominates the PL spectrum. The SR mode demonstrates a superlinear dependence of the intensity and radiative decay rate on the excitation power and its intensity increases at elevated temperatures compared to the excitonic emission. The photoluminescence delay time is much shorter for the SR mode indicating that the relaxation of hot excitons can occur via stimulated scattering processes. The specific behavior of the SR emission can have a strong potential for different applications such as optical logic devices, superluminescent diodes, optical switches, and low-threshold lasers. Time-resolved photoluminescence image at low temperature for the Bragg structure consisting of InAs monolayer-based quantum wells (inset).

  • 40.
    Semchuk, OY
    et al.
    National Academy of Sciences of Ukraine.
    Willander, Magnus
    Göteborg University and Chalmers University of Technology.
    Karlsteen, M
    Göteborg University and Chalmers University of Technology.
    Wave function and quasi-energy of conduction electrons in a field of coherent light beams2004In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 241, no 11, p. 2549-2554Article in journal (Refereed)
    Abstract [en]

    In this work the influence of high-frequency coherent light beams (CLB) on the motion of conduction electrons in a crystalline phase is studied. The wave function and the quasi-energy of conduction electrons are calculated. It is shown that a force that is associated with a pressure from the CLB influences the conduction electrons. A new approach to construct the kinetic equation, that takes into account the effects due to a CLB field that acts as the elementary processes for quasi-particle interaction in a crystalline phase, is presented.

  • 41.
    Shubina, T. V.
    et al.
    Ioffe Institute, Russia.
    Jmerik, V. N.
    Ioffe Institute, Russia.
    Davydov, V. Yu.
    Ioffe Institute, Russia.
    Kazanov, D. R.
    Ioffe Institute, Russia.
    Smirnov, A. N.
    Ioffe Institute, Russia.
    Nechaev, D. V.
    Ioffe Institute, Russia.
    Kuznetsova, N.
    Ioffe Institute, Russia.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, S. V.
    Ioffe Institute, Russia.
    III-nitride microcrystal cavities with quasi whispering gallery modes grown by molecular beam epitaxy2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 253, no 5, p. 845-852Article in journal (Refereed)
    Abstract [en]

    This paper analyzes current trends in fabrication of III-nitride microresonators exploiting whispering gallery modes. Novel cup-cavities are proposed and their fabrication from GaN and InN by molecular beam epitaxy on patterned substrates is described. These cup-cavities can concentrate the mode energy in a subwavelength volume. Their mode energies are stable up to room temperature, being identical in large microcrystals. In these cavities, mode switching can be realized by means of refractive index variation. Cup-cavity modes, being inferior to plasmonic resonances in the respect of integral emission enhancement, have advantages for spectrally selective amplification of quantum transitions in site-controlled nano-emitters. (C) 2016 WILEY-VCH Verlag GmbH amp; Co. KGaA, Weinheim

  • 42.
    Shubina, T. V.
    et al.
    Ioffe Institute, Russia.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Toropov, A. A.
    Ioffe Institute, Russia.
    Recombination dynamics in arrays of II-VI epitaxial quantum dots with Forster resonance energy transfer2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 4, article id UNSP 1600414Article in journal (Refereed)
    Abstract [en]

    We report on time-resolved photoluminescence (TR PL) studies of Forster resonance energy transfer (FRET) between epitaxial CdSe/ZnSe quantum dots (QDs). To prove the existence of FRET, we use two sheets of QD arrays, formed from CdSe insertions of different nominal thicknesses, which are separated by a ZnSe barrier of a variable width. The FRET mechanism manifests itself as acceleration of the PL decay of the energy-donating QD sheet when the barrier width is decreased. The Forster radius of about 10.5nm is determined by fitting TR PL data. Besides, our findings exhibit the inhomogeneous distribution of QD sizes within the QD arrays and the influence of FRET efficiency on recombination dynamics of forbidden exciton states. TR PL images showing the acceleration of PL decay of the energy-donating QD array with decreasing the barrier width.

  • 43.
    Shubina, Tatiana
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ivanov, SV
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Toropov, AA
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Sorokin, SV
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Lebedev, Alexander
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kyutt, RN
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Solnyshkov, DD
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, JP
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Willander, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Waag, A
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Landwehr, G
    AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Chalmers, S-41296 Gothenburg, Sweden Gothenburg Univ, S-41296 Gothenburg, Sweden Univ Ulm, Abt Halbleiterphys, D-89081 Ulm, Germany Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany.
    Interface effects in type-II CdSe/BeTe quantum dots2002In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 229, no 1, p. 489-492Article in journal (Refereed)
    Abstract [en]

    We report on optical and structural studies of the interface symmetry in CdSe/BeTe multiple-layer structures containing self-assembled quantum dots. Temperature and decay behavior of the broad photoluminescence (PL) band is consistent with the type-II transitions involving deeply localized electron states. Large linear in-plane polarization of the PL (up to 80%) is observed, implying the C-2v (or lower) symmetry of the individual places of the electron localization.

  • 44.
    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.

  • 45.
    Shubina, Tatiana
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Toropov, AA
    Russian Acad Sci, AF Ioffe Phys Tech Inst, Ctr Nanoheterostruct Phys, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-581833 Linkoping, Sweden.
    Lebedev, Alexander
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ivanov, SV
    Russian Acad Sci, AF Ioffe Phys Tech Inst, Ctr Nanoheterostruct Phys, St Petersburg 194021, Russia Linkoping Univ, Dept Phys & Measurement Technol, S-581833 Linkoping, Sweden.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Micro-photoluminescence spectroscopy of exciton-polaritons in GaN with the wave vector k normal to the c-axis2001In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, no 2, p. 481-484Article in journal (Refereed)
    Abstract [en]

    We report on polarized micro-photoluminescence (mu -PL) and micro-reflectance (mu -R) studies of GaN layers grown by HVPE. A strong pi -polarized component in the vicinity of A exciton is observed in the mu -PL and attributed as a mixture of a bound B exciton, dominating at low temperature, and scattered A exciton-polariton states prevailing at higher temperatures. Temperature variation of exciton energies in the mu -R spectra reveals strain-induced difference between the top surface and the cleaved edges.

  • 46.
    Slomski, Michael
    et al.
    North Carolina State University, USA.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. North Carolina State University, USA.
    Leach, Jacob H.
    Kyma Technology Inc, USA.
    Muth, John F.
    North Carolina State University, USA.
    Paskova, Tania
    North Carolina State University, USA.
    Thermal conductivity of bulk GaN grown by HVPE: Effect of Si doping2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 8, article id 1600713Article in journal (Refereed)
    Abstract [en]

    The thermal conductivity of bulk GaN grown by Hydride Phase Vapor Epitaxy with intentional Si doping was measured using the 3 method. The effect of Si concentration ranging from 1.6x10(16) to 7x10(18)cm(-3) on the thermal conductivity was studied over the temperature range of 295-470K. The room temperature thermal conductivity was found to decrease with increasing Si doping from 245 to 210W/m.K. Also, for each Si doped sample the thermal conductivity decreases with increasing temperature. The experimental data were analysed by a modified Callaway model and the contribution of different resistive phonon scattering process was examined. It was found that in n-type GaN the phonon-free-electron scattering became an important resistive process that leads to a reduction of the thermal conductivity at high temperatures. At the highest free electron concentrations, electronic thermal conduction was found to play a role in addition to lattice thermal conduction and compete with the effects of phonon-free-electron scattering. (C) 2017 WILEY-VCH Verlag GmbH amp; Co. KGaA, Weinheim

  • 47. Strocov, V.N.
    et al.
    Schmitt, T
    Rubensson, J. -E
    Blaha, P
    Paskova, Tanja
    Linköping University, Department of Physics, Chemistry and Biology.
    Nilsson, P.O.
    Band structure effects in nitrogen K-edge resonant inelastic X-ray scattering from GaN2004In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 241, no 7Article in journal (Refereed)
    Abstract [en]

    Systematic experimental data on resonant inelastic X-ray scattering (RIXS) in GaN near the N K-edge are presented for the first time. Excitation energy dependence of the spectral structures manifests the band structure effects originating from momentum selectivity of the RIXS process. This finding allows obtaining k-resolved band structure information for GaN crystals and nanostructures. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 48. Terentev, Ya. V.
    et al.
    Toropov, A. A.
    Sorokin, S. V.
    Lebedev, A. V.
    Ivanov, S. V.
    Kopev, P. S.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Semimagnetic ZnMnSe/CdSe Fractional Monolayer Superlattice as an Injector of Spin-Polarized Carriers2002In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 229, no 2, p. 765-768Article in journal (Refereed)
    Abstract [en]

    We report on effective injection of spin-oriented carriers from a semimagnetic semiconductor structure to a non-magnetic ZnCdSe/ZnSe quantum well (QW). A short-period ZnMnSe/CdSe fractional monolayer superlattice was used as a spin injector. The carriers are photo-generated in the semimagnetic region, spin-polarized via the effect of giant Zeeman splitting and then injected into the non-magnetic QW. The spin injection efficiency was estimated by circular polarization measurements of recombination emission from the QW. The maximal detected degree of the spin polarization is about 25%.

  • 49.
    Toropov, A.A.
    et al.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Sedova, I.V.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Sorokin, S.V.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Terent'ev, Ya.V.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Ivchenko, E.L.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Lykov, D.N.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Ivanov, S.V.
    Ioffe Physico-Technical Institute, Polytehknicheskaya 26, 194021 St. Petersburg, Russian Federation.
    Bergman, Peder
    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 .
    III-V/II-VI heterovalent double quantum wells2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 4, p. 819-826Article in journal (Refereed)
    Abstract [en]

    We report on design, fabrication by molecular beam epitaxy, and photoluminescence (PL) studies of III-V/II-VI heterovalent structures containing a GaAs/AlGaAs/ZnSe/ZnCdMnSe double quantum well (QW). The studies of temperature-dependent and time-resolved PL have provided an insight into the nature of the exciton localization potential induced by the heterovalent interface. It is found that under the resonant conditions the observed emission mostly originates from the recombination of excitons confined in type II quantum-dot-like structures, where the holes are localised within the GaAs QW due to the well width fluctuations and the electrons are localized in the plane of the ZnCdMnSe QW due to the fluctuations of the conduction band offset at the heterovalent interface, induced by random variation of the interface microscopic structure. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA,.

  • 50. Tuomisto, F
    et al.
    Hautakangas, S
    Makkonen, I
    Ranki, V
    Puska, MJ
    Saarinen, K
    Bockowski, M
    Suski, T
    Paskova, Tanja
    Linköping University, The Institute of Technology. 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 .
    Xu, X
    Look, DC
    Dissociation of V-Ga-O-N complexes in HVPE GaN by high pressure and high temperature annealing2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 7, p. 1436-1440Article in journal (Refereed)
    Abstract [en]

    We have used positron annihilation spectroscopy to study the high-pressure annealing induced thermal recovery of vacancy defects in free-standing GaN grown by hydride vapor phase epitaxy (HYPE). The results show that the in-grown Ga vacancy complexes recover after annealing at 1500-1700 K. Comparison of the experimental positron data with ab-initio calculations indicates that the Doppler broadening measurement of the electron momentum distribution is sensitive enough to distinguish between the N and O atoms surrounding the Ga vacancy. We show that the difference between the isolated V-Ga in electron irradiated GaN and the V-Ga-O-N complexes in highly O-doped GaN is clear, and the Ga vacancy related defect complexes that start dissociating at 1500 K can be identified as V-Ga-O-N pairs.

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