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  • 251.
    Paskov, Plamen
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Monemar, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Toropov, A.
    Bergman, Peder
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Usui, A.
    Two-electron transition spectroscopy of shallow donors in bulk GaN2007Ingår i: Proc. of the International Workshop on Nitride Semiconductors IWN2006,2006, Physica Status Solidi C: WILEYVCH Verlag GmbH & Co. KGaA , 2007, s. 2601-Konferensbidrag (Refereegranskat)
  • 252.
    Paskov, Plamen P.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Monemar, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Optical Properties of III-Nitride Semiconductors2017Ingår i: Handbook of GaN Semiconductor Materials and Devices / [ed] Wengang (Wayne) Bi, Haochung (Henry) Kuo, Peicheng Ku, Bo Shen, Boca Raton: CRC Press, 2017, 1, s. 87-116Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The optical properties of the group-III-nitride materials are obviously of direct relevance for optoelectronic applications, but experiments measuring optical properties also give information on a range of electronic properties. There is already a wealth of data in the literature on the optical properties of III-nitrides [1–4], and here we will concentrate on some of the most recent additions to the scientific knowledge. The focus, looking at the present situation concerning technical applications of these materials, has been on GaN, InGaN, and AlGaN in recent decades. AlGaN materials are important for ultraviolet (UV) emitters and high electron mobility transistor (HEMT) structures and AlGaN optical properties have accordingly been studied over the entire Al composition range. InGaN materials (with In content <50%) have also been studied extensively, and the light-emitting diode (LED) applications based on InGaN/GaN quantum structures have already been awarded a Nobel Prize in 2014. However, the applications of InN are lagging behind. The development of growth procedures for InN and In-rich InGaN has been difficult, and their optical properties were consequently much less studied in the past.

  • 253.
    Paskov, Plamen P.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Monemar, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Point Defects in group-III nitrides2018Ingår i: Defects in Advanced Electronic Materials and Novel Low Dimensional Structures / [ed] Jan Stehr, Irina Buyanova, Weimin Chen, Woodhead Publishing Limited, 2018, 1, s. 27-61Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Point defects in semiconductors play a fundamental role for the material properties. Dopants like impurities forming shallow donors and acceptors provide the means of controlling the electrical conductivity of the material, which is the basis of many applications in devices. Native defects like vacancies and interstitial atoms, and their combination with impurities introduce, mostly unwanted deep levels in the bandgap, and thus may serve as traps or recombination centers for the carriers. Some of these defects are introduced during the growth of the material, others by the processing steps necessary in the device production. In this chapter, we present current knowledge about point defects in the III-nitrides based on recent works, both experimental and theoretical, in the field. Materials discussed are AlN, GaN and InN and the ternary alloys between them.

  • 254.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Holtz, Per-Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Anisotropy of the free exciton emission in GaN grown on a-plane sapphire2002Ingår i: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 190, nr 1, s. 75-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the anisotropic in-plane strain on the optical response of GaN layers grown on a-plane sapphire is investigated. A splitting of the G5 states of the A and B free excitons into two components, polarized parallel and perpendicular to the strain direction, is observed. The experimental results are discussed in the framework of the effective exciton Hamiltonian formalism.

  • 255.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Holtz, Per-Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Internal structure of free excitons in GaN2001Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, nr 2, s. 467-470Artikel i tidskrift (Refereegranskat)
    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.

  • 256.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Holtz, Per-Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Polarisation dependent spectroscopy of the near bandgap emission in free-standing GaN2004Ingår i: 2003 MRS Fall Meeting,2003, 2004, s. Y6.1.1-Konferensbidrag (Refereegranskat)
  • 257.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Holtz, Per-Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Polarized photoluminescence of exciton-polaritons in free-standing GaN2004Ingår i: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 201, nr 4, s. 678-685Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the polarization properties of the exciton-polariton modes in GaN. The dispersion curves and the expected emission lineshape of polaritons for all polarization configurations are calculated taking into account the spatial dispersion and the simultaneous exciton-photon coupling of all optically active states. An experimental study of the exciton-polariton luminescence in a free-standing GaN layer is also performed. The spectra reveal a clear difference between the emissions polarized perpendicular and parallel to the c-axis of the crystal. The experimental results are discussed in terms of optical selection rules and population of the polariton states. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 258.
    Paskov, Plamen
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Paskova, Tanja
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Polarized photoluminescence study of free and bound excitons in free-standing GaN2004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study of the polarization properties of the exciton emission in GaN is presented. Photoluminescence measurements are performed for light propagation perpendicular to the c axis of a free standing layer grown by hydride vapor phase epitaxy. Emission from different polariton branches of the Γ5 and Γ1, free exciton states are identified for the E ⊥ c and E∥c polarizations, respectively. The mixed-mode transverse-longitudinal state of the A exciton is also observed in the E∥c polarized spectra. Donor-bond excitons involving a hole from the A and B valence bands are clearly distinguished and are found to follow the optical selection rules of the free excitons. The temperature dependence of the emission intensities is also investigated and the exciton thermalization processes for both polarizations are discussed.

  • 259.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Holtz, Per-Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Spin-exchange splitting of excitons in GaN2001Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 64, nr 11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on polarization-dependent photoluminescence measurements in thick GaN layers. The free-exciton emission peaks are found to appear at different energy positions in the spectra polarized perpendicular and parallel to the c, axis, In the case of E parallel toc polarization, emission from the spin-triplet state of the A exciton is observed and the singlet-triplet splitting resulting from the exchange interaction is obtained. In a highly strained layer, the splitting between the two dipole-allowed states of the B exciton is also observed. The experimental data are analyzed using an appropriate exciton Hamiltonian in a wurtzite crystal. The stress dependence of the energy splitting between the exciton states is studied and the exchange interaction constant in GaN, gamma = 0.58 +/-0.05 meV, is determined.

  • 260.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Figge, S.
    Hommel, D.
    Haskell, B.A.
    Fini, P.T.
    Speck, S.J.
    Nakamura, S.
    Optical properties of nonpolar a-plane GaN layers2006Ingår i: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 40, nr 4-6 SPEC. ISS., s. 253-261Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied optical properties of nonpolar a-plane GaN layers grown on r-plane sapphire by metalorganic chemical vapor deposition and hydride vapor phase epitaxy using different nucleation schemes. Several emission bands, which are not typical for c-plane GaN, are observed in the photoluminescence spectra and their excitation-intensity, temperature, and polarization dependencies are examined. In addition, the spatial distribution of the emissions was examined by cathodoluminescence imaging and relations of the different emissions with particular structural features in the layers are revealed. The results are discussed with emphasis on the origin of the emission line and particular recombination mechanisms. © 2006 Elsevier Ltd. All rights reserved.

  • 261.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Schifano, R.
    Malinauskas, T.
    Paskova, T.
    Bergman, Peder
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Figge, S.
    Hommel, D.
    Haskell, B.A.
    Fini, P.T.
    Speck, J.S.
    Nakamura, S.
    Photoluminescence of a -plane GaN: comparison between MOCVD and HVPE grown layers2006Ingår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 6, s. 1499-1502Artikel i tidskrift (Refereegranskat)
  • 262.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Schifano, R.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskova, T.
    Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany.
    Figge, S.
    Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany.
    Hommel, D.
    Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany.
    Emission properties of a -plane GaN grown by metal-organic chemical-vapor deposition2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, nr 9, s. 093519-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the emission properties of nonpolar a -plane GaN layers grown on r -plane sapphire. Temperature-, excitation-density-, and polarization-dependent photoluminescences and spatially resolved microphotoluminescence and cathodoluminescence are employed in order to clarify the nature of the different emission bands in the 3.0-3.5 eV spectral range. In the near band-edge region the emission lines of the donor-bound excitons (3.472 eV) and free excitons (3.478 eV) are resolved in the polarized low-temperature spectra, indicating a good quality of the layers. At low energies two other emissions bands with intensity and shape varying with the excited area are observed. The 3.42 eV emission commonly attributed to the excitons bound to basal plane stacking faults shows thermal quenching with two activation energies (7 and 30 meV) and an S-shaped temperature dependence of the peak position. This behavior is analyzed in terms of hole localization in the vicinity of the stacking faults. The emission band that peaked at 3.29 eV is found to blueshift and saturate with increasing excitation intensity. The spatially resolved cathodoluminesence measurements show that the emission is asymmetrically distributed around the triangular-shaped pits occurring at the surface. The 3.29 eV emission is suggested to involve impurities, which decorate the partial dislocation terminating the basal stacking faults. © 2005 American Institute of Physics.

  • 263.
    Paskov, Plamen
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Schifano, R
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Malinauskas, T
    Bergman, Peder
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Figge, S
    Hommel, D
    Structural defect-related emissions in nonpolar a-plane GaN2006Ingår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 376, s. 473-476Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied the optical emission properties of a-plane GaN layers grown on r-plane sapphire by metalorganic chemical vapor deposition. Together with the typical band edge exciton emission, the photoluminescence (PL) spectra reveal three low-energy emissions peaked at 3.42, 3.34 and 3.29eV. which are related to structural defects. Temperature and excitation dependent stationary PL and the time-resolved PL have been employed in order to understand the exact origin of these emissions. The 3.42 and 3.34eV emissions are found to be of an intrinsic origin and are associated with carriers localized at stacking faults. The emission at 3.29eV shows a donor-acceptor pair behavior suggesting that impurities attached to structural defects most likely partial dislocations terminating stacking faults are involved. (c) 2005 Elsevier B.V. All rights reserved.

  • 264. Paskova, T.
    et al.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Suski, T.
    Bockowski, M.
    Ashkenov, N.
    Schubert, M.
    Bending in HVPE GaN free-standing films: effects of laser lift-off, polishing and high temperature annealing2006Ingår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 3, s. 1475-1478Artikel i tidskrift (Refereegranskat)
  • 265. Paskova, T.
    et al.
    Hommel, D.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Bockowski, M.
    Suski, T.
    Grzegory, I.
    Tuomisto, T.
    Saarinen, K.
    Ashkenov, N.
    Schubert, M.
    Effect of high-temperature annealing on the residual strain and bending of freestanding GaN films grown by hydride vapor phase epitaxy2006Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, nr 14, s. 141909-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of high-temperature high-pressure annealing on the residual strain, bending, and point defect redistribution of freestanding hydride vapor phase epitaxial GaN films was studied. The bending was found to be determined by the difference in the in-plane lattice parameters in the two faces of the films. The results showed a tendency of equalizing the lattice parameters in the two faces with increasing annealing temperature, leading to uniform strain distribution across the film thickness. A nonmonotonic behavior of structural parameters with increasing annealing temperature was revealed and related to the change in the point defect content under the high-temperature treatment. © 2006 American Institute of Physics.

  • 266. Paskova, T.
    et al.
    Kroeger, R.
    Figge, S.
    Hommel, D.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Preble, E.
    Hanser, A.
    Williams, N.M.
    Tutor, M.
    High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire2006Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, nr 5, s. 051914-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thick GaN bars with [1120] orientation have been sliced from GaN boules grown on freestanding films by hydride vapor phase epitaxy (HVPE) in the [0001] direction. High-resolution x-ray diffraction and transmission electron microscopy have been used to study the structural quality and defect distribution in the material in comparison to heteroepitaxially grown thick HVPE-GaN films grown in the [1120] direction on (1102)-plane sapphire. It is demonstrated that while the heteroepitaxial material possesses a high density of stacking faults and partial dislocations, leading to anisotropic structural characteristics, the (1120)-plane bulk GaN, sliced from boules, exhibits low dislocation density and narrow rocking curves with isotropic in-plane character. © 2006 American Institute of Physics.

  • 267. Paskova, T.
    et al.
    Kroeger, R.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Figge, S.
    Hommel, D.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Haskell, B.A.
    Fini, P.
    Speck, J.S.
    Nakamura, S.
    Microscopic emission properties of nonpolar a-plane GaN grown by HVPE2006Ingår i: International Symposium on Integrated Optoelectronic Devices Photonics West 2006,2006, Proc. SPIE 6121: SPIE Digital Library , 2006, s. 47-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Invited talk

  • 268.
    Paskova, Tanja
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Arnaudov, B.
    Paskov, Plamen
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Goldys, E.M.
    Hautakangas, S.
    Saarinen, K.
    Sodervall, U.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Dominating behaviour of the donor-acceptor pair emission in mass-transport GaN2005Ingår i: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 772, s. 261-262Artikel i tidskrift (Refereegranskat)
  • 269.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Arnaudov, B.
    Faculty of Physics, Sofia University, Sofia 1164, Bulgaria.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Goldys, E.M.
    Macquare University, Sydney, NSW 2109, Australia.
    Hautakangas, S.
    Helsinki University of Technology, Espoo 02015 HUT, Finland.
    Saarinen, K.
    Helsinki University of Technology, Espoo 02015 HUT, Finland.
    Sodervall, U.
    Södervall, U., Chalmers University of Technology, S-412 96 Göteborg, Sweden.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Donor-acceptor pair emission enhancement in mass-transport-grown GaN2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, nr 3, s. 033508-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dominating donor-acceptor pair (DAP) emission at about 3.27 eV is observed in the photoluminescence and cathodoluminescence spectra of intentionally undoped mass-transport (MT)-grown GaN, while only a weak presence of the DAP emission is recorded in the as-grown hydride vapor phase epitaxial GaN. A comparative study of impurity and native defect incorporation in the as-grown and MT GaN was performed, showing a significant increase of oxygen and empty clusters involving Ga vacancy and oxygen in the MT GaN. Based on the observed results as well as on doping analysis of the structure and kinetic analysis of the emission intensities, we propose an acceptorlike complex, creating a state as a semiclassical potential well near the valence-band top due to the local tensile strain caused by the empty clusters to be responsible for the dominating behavior of the DAP emission. © 2005 American Institute of Physics.

  • 270.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Becker, L.
    Böttcher, T.
    Hommel, D.
    Paskov, Plamen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Monemar, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Bending in HVPE grown GaN films: origin and reduction possibilities2007Ingår i: Proc. of the International Workshop on Nitride Semiconductors IWN2006,2006, Physica Status Solidi C, vol. 4: WILEYVCH Verlag GmbH & Co. KGaA , 2007, s. 2256-Konferensbidrag (Refereegranskat)
    Abstract [en]

      

  • 271.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Becker, L.
    Böttcher, T.
    Hommel, D.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Effect of sapphire-substrate thickness on the curvature of thick GaN films grown by hydride vapor phase epitaxy2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, nr 12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of sapphire-substrate thickness on the curvature and stress in thick hydride vapor phase epitaxial GaN films was studied by high-resolution x-ray diffraction at variable temperatures. The curvature was found to have the maximum value for comparable thicknesses of the film and the substrate, while the stress at the film surface decreases with increasing film thickness and increases with increasing substrate thickness, which is in very good agreement with the simulation results. The curvature at the growth temperature was found to be strongly influenced by the value of the intrinsic tensile strain, which is determined by the film/substrate thickness ratio. © 2007 American Institute of Physics.

  • 272.
    Paskova, Tanja
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Darakchieva, Vanya
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Paskov, Plamen
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Valcheva, E.
    Persson, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Arnaudov, B.
    Tungasmita, S.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Nonpolar a-plane HVPE GaN: growth and in-plane anisotropic properties2005Ingår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 2, s. 2027-2031Artikel i tidskrift (Refereegranskat)
  • 273.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Birch, Jens
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Valcheva, E
    Persson, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Arnaudov, B
    Tungasmitta, S
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Properties of nonpolar a-plane GaN films grown by HVPE with AlN buffers2005Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 281, nr 1, s. 55-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of high temperature AlN buffer layers on the morphology, structural and optical characteristics of a-plane GaN grown by hydride vapour phase epitaxy on r-plane sapphire was investigated. While the morphology of the a-GaN was found to be significantly improved by using a-plane AlN buffer layer similarly to the effect observed in c-plane hydride vapour phase epitaxy GaN growth, the microstructure ensemble was revealed to be more complicated in comparison to that of the c-plane GaN. Higher dislocation density and prismatic stacking faults were observed. Moreover, in-plane anisotropic structural characteristics were revealed by high resolution X-ray diffraction employing azimuthal dependent and edge X-ray measurement symmetric geometry. In addition, the near band edge photo luminescence peaks, red-shifted with respect to that in c-plane GaN were observed. The latter were explained by the influence of the higher defect density and more complex strain distribution. (c) 2005 Elsevier B.V. All rights reserved.

  • 274.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Sodervall, U.
    Södervall, U., Chalmers University of Technology, S-412 96 Göteborg, Sweden.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Growth and separation related properties of HVPE-GaN free-standing films2002Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 246, nr 3-4, s. 207-214Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Hydride vapour phase epitaxial GaN layers with thicknesses in the range 10-150µm grown directly on sapphire or using metalorganic vapour phase deposited GaN templates have been separated by laser-induced lift-off technique. Both faces of the free-standing films have been studied by photoluminescence and high-resolution X-ray measurements and stress analysis has been performed. A comparison with as-grown films reveals the changes in the properties of the material after the separation process. The separation conditions are found to be responsible for the bowing in the free-standing GaN films while the type and intensity of emission bands, as well as defect and impurity distributions are related only to the growth conditions. The residual strain in the free-standing layers is attributed to both non-optimized separation conditions and non-uniform defect density in the films. © 2002 Elsevier Science B.V. All rights reserved.

  • 275.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Valcheva, E
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bottcher, T
    Roder, C
    Hommel, D
    Hydride vapor-phase epitaxial GaN thick films for quasi-substrate applications: Strain distribution and wafer bending2004Ingår i: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 33, nr 5, s. 389-394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The strain distribution in thick hydride vapor-phase epitaxial (HVPE)-GaN layers grown on metal-organic vapor-phase epitaxial GaN templates was studied by means of photoluminescence, x-ray mapping, and lattice parameter analysis. A variable temperature x-ray study of the film curvature was used for verification of the strain type. The relation between the strain inhomogeneity and the wafer bending in films residing on sapphire and freestanding on the thickness of the layer and the substrate is analyzed. Possibilities to improve the uniformity of the film characteristics and to reduce the bending of the HVPE-GaN films are discussed.

  • 276.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Valcheva, E.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Heuken, M.
    Aixtron AG, 52072 Aachen, Germany.
    Growth of GaN on a-plane sapphire: In-plane epitaxial relationships and lattice parameters2003Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 240, nr 2, s. 318-321Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 277.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Valcheva, E.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Heuken, M.
    Aixtron AG, Kackerstrasse 15-17, D-52072 Aachen, Germany.
    In-plane epitaxial relationships between a-plane sapphire substrates and GaN layers grown by different techniques2003Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 257, nr 1-2, s. 1-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied GaN films grown on a-plane sapphire substrate by both hydride vapour phase epitaxy (HVPE) and metalorganic vapour phase epitaxy (MOVPE) using X-ray diffraction and transmission electron microscopy. The in-plane orientation relationships between the epitaxial films and the substrate are determined to be [1 1 2¯ 0]GaN?[0 0 0 1] sapphire and [1 1¯ 0 0]GaN?[1 1¯ 0 0] sapphire in the HVPE growth, while [1 1¯ 0 0] GaN?[0 0 0 1]sapphire and [1 1 2¯ 0] GaN?[1 1¯ 0 0]sapphire are found in the MOVPE growth. In a few films of both types a simultaneous presence of two domains, representing the two in-plane relationships, is observed although the preferable one in each type of films is strongly dominating. We propose that the two in-plane orientations of GaN are generally possible on the a-sapphire substrate and are related to the atom termination of the sapphire surface determined by the substrate pre-treatment used in the different growth methods. © 2003 Elsevier B.V. All rights reserved.

  • 278.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Goldys, E.M.
    Div. of Info. and Commun. Sciences, Macquarie University, Sydney, NSW 2109, Australia.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Wahab, Qamar Ul
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Wilzén, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    de Jong, Michel P
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Mass transport growth and optical emission properties of hydride vapor phase epitaxy GaN2001Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, nr 26, s. 4130-4132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optical emission properties of mass-transport regions of GaN grown by hydride vapor phase epitaxy are studied by cathodoluminescence imaging and spectroscopy. A strong donor-acceptor pair emission is observed from the mass-transport regions. Spatially resolved cathodoluminescence reveals a strong intensity contrast between the exciton and donor-acceptor bands from mass-transport and nontransport regions. Focused Auger electron and x-ray photoelectron spectroscopies were employed to investigate the impurity incorporation in the different regions. A preferential moderate increase of residual impurity incorporation or redistribution in mass-transport regions is suggested to be responsible for the observed change of the dominant radiative mechanism. © 2001 American Institute of Physics.

  • 279.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Goldys, E.M.
    Semiconduct. Sci. and Technol. Labs., Macquarie University, Sydney, NSW 2109, Australia.
    Yakimova, Rositsa
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Svedberg, E.B.
    Henry, Anne
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Influence of growth rate on the structure of thick GaN layers grown by HVPE2000Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 208, nr 1, s. 18-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thick GaN films grown by hydride vapour phase epitaxy have been investigated by cathodoluminecsence, X-ray diffraction, and photoluminescence. Cross-sectional studies of thick GaN layers grown on sapphire without buffers reveal three zones: a highly disordered interface region, a columnar defective region and a good quality main region of the layer. The influence of the highly doped columnar region on the surface morphology and crystal structure of the layers has been studied. We show that the columnar region influences the material quality more strongly in thinner films. Thicker layers exhibit improved morphology with lower surface pit density and better crystal quality shown in photoluminescence and X-ray diffraction spectra. The relationship between the near-interface columnar structures and surface pits is revealed. A strong effect of the growth rate on the structure of thick layers is found. The results suggest that GaN layers with optimum crystalline quality may be obtained by varying the growth rate during growth.

  • 280.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Hanser, A.D.
    Preble, E.
    Evans, K.
    Kroeger, R.
    Toumisto, F.
    Kersting, R.
    Alcorn, R.
    Ashley, S.
    Pagel, C.
    Valcheva, E.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Defect and emission distributions in bulk GaN grown in polar and nonpolar directions: a comparative analysis2008Ingår i: Proceedings of SPIE - The International Society for Optical Engineering, 2008, s. 68940D1-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We have investigated bulk GaN material grown by HVPE either in the conventional polar [0001] direction and subsequently sliced with nonpolar surfaces or grown in the nonpolar [11-20] direction. Spatially resolved techniques such as cathodoluminescence imaging and transmission electron microscopy, as well as profile measuring techniques such as positron annihilation spectroscopy and secondary ion mass spectroscopy were employed to directly visualize the extended structural defects, and point defect (impurity and vacancy) distributions along the growth axes. A comparative analysis of the results shows a distinctive difference in the distribution of all kind of defects along the growth axes. A significant decrease in the defect density in material grown along the polar direction, in contrast to the constant behavior of the high defect density in material grown along the nonpolar direction points out the low-defect superior quality of the former material and indicates the preferable way of producing high-quality GaN substrates with nonpolar surfaces.

  • 281.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Kroeger, R.
    Hommel, D.
    Paskov, Plamen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Monemar, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Preble, E.
    Hanser, A.
    Williams, N.M.
    Tutor, M.
    Nonpolar a- and m-plane bulk GaN sliced from boules: structural and optical characteristics2007Ingår i: Proc. of the International Workshop on Nitride Semiconductors IWN2006,2006, Physica Status Solidi C, vol. 4: WILEYVCH Verlag GmbH & Co. KGaA , 2007, s. 2536-Konferensbidrag (Refereegranskat)
  • 282.
    Paskova, Tanja
    et al.
    University of Bremen, Institute of Solid State Physics, Bremen, Germany.
    Paskov, Plamen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Darakchieva, Vanya
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Kröger, Roland
    University of Bremen, Bremen, Germany.
    Hommel, Detlef
    University of Bremen, Bremen, Germany.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Lourdudoss, Sebastian
    Royal Institute of Technology, Kista, Sweden.
    Preble, Edward
    Kyma Technologies Inc., Raleigh, NC, United States.
    Hanser, Andrew
    Kyma Technologies Inc., Raleigh, NC, United States.
    Williams, Mark N.
    Kyma Technologies Inc., Raleigh, NC, United States.
    Tudor, Michael
    Kyma Technologies Inc., Raleigh, NC, United States.
    Strain-free low-defect-density bulk GaN with nonpolar orientation2006Ingår i: MRS Proceedings 2006 MRS Fall Meeting: Symposium I – Advances in III-V Nitride Semiconductor Materials and Devices / [ed] C.R. Abernathy, H. Jiang, J.M. Zavada, New York, NY, United States: Materials Research Society, 2006, s. I3.4-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Bulk GaN sliced in bars along (11-20) and (1-100) planes from a boule grown in the [0001] direction by HVPE was confirmed as strain free material with a low dislocation density by using several characterization techniques. The high-structural quality of the material allows photoluminescence studies of free excitons, principal donor bound excitons and their two-electron satellites with regard to the optical selection rules. Raman scattering study of the bulk GaN with nonpolar orientations allows a direct access to the active phonon modes and a direct determination of their strain-free positions.

  • 283.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Tungasmita, Sukkaneste
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Birch, Jens
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Defect reduction in HVPE growth of GaN and related optical spectra2001Ingår i: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 183, nr 1, s. 197-203Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    GaN technology is still based on highly mismatched heteroepitaxial growth on foreign substrates, and therefore needs to overcome a high defect density and a high level of stress in the epitaxial layers. Various attempts have been made to reduce the defects and stress in thick GaN layers. We here report a reduction of the defect density in thick GaN layers grown by hydride vapour phase epitaxy, using regrowth on free-standing GaN films, as well as introducing an AlN buffer and AlN interlayer in the growth sequence. Special focus is put on the optical properties of the material.

  • 284.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Goldys, E. M.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Södervall, U
    Godlewski, M
    Zielinski, M
    Valcheva, E
    Carlström, C
    Wahab, Qamar Ul
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Characterization of mass-transport grown GaN by hydride vapour-phase epitaxy2004Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 273, nr 1-2, s. 118-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A comprehensive study of the morphological, optical and microstructural properties of mass-transport (MT) and conventionally grown GaN by hydride vapour-phase epitaxy is presented. Spatially resolved techniques have been utilized to reveal in a comparative way, the characteristics of the material grown either in predominant vertical or lateral growth modes. A strong donor-acceptor pair (DAP) emission is observed from the MT regions with a distinctive intensity contrast between the exciton and DAP emission bands from MT and nontransport regions. Secondary ion mass spectroscopy and imaging were employed to investigate the impurity incorporation into different regions. An increase of residual oxygen and aluminium impurity concentrations was found in the MT areas. In addition, positron annihilation spectroscopy showed a strong signal of Ga vacancy clusters in the MT grown material. The increase of the point defect concentrations of both Ga vacancy and oxygen impurity, most likely forming defect complexes, is related to the enhancement of the DAP emission. © 2004 Elsevier B.V. All rights reserved.

  • 285.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Valcheva, E
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Birch, Jens
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Kasic, A
    Arnaudov, B
    Tungasmita, Sukkaneste
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Polar and nonpolar GaN grown by HVPE: Preferable substrates for nitride-based emitting devices2004Ingår i: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 201, nr 10, s. 2265-2270Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on hydride vapor phase epitaxial growth of thick nonpolar GaN films on r-plane sapphire in comparison with polar GaN films on c-plane sapphire substrates with AlN buffer layers, aiming at developing of their quasi-substrate application. Both the thick films and the buffers were identified to have single crystalline structures. The microstructure of the films was studied by transmission electron microscopy. High resolution X-ray diffraction mapping and photoluminescence measurements were employed to characterize the strain present in both polar and nonpolar GaN films. In contrast to c-plane GaN, which is always characterised by isotropic in-plane properties, the a-plane GaN shows a strong in-plane anisotropy of the growth rate, morphology and strain distribution. Different defect, impurity and free carrier concentrations were observed in the polar and nonpolar material.

  • 286.
    Paskova, Tanja
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Suski, T.
    Bockowski, M.
    Paskov, Plamen
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Darakchieva, Vanya
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Tuomisto, F.
    Saarinen, K.
    Ashkenov, N.
    Schubert, M.
    Röder, C.
    Hommel, D.
    High pressure annealing of HVPE GaN free-standing films: redistribution of defects and stress2005Ingår i: MRS Fall Meeting,2004, Materials Research Society , 2005, s. E8.18.11-E8.18.11Konferensbidrag (Övrigt vetenskapligt)
  • 287.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Tungasmita, Sukkaneste
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Valcheva, E
    Linkoping Univ, IFM, S-58183 Linkoping, Sweden Univ Sofia, Fac Phys, Sofia 1164, Bulgaria Aixtron AG, D-52072 Aachen, Germany.
    Svedberg, EB
    Arnaudov, B
    Linkoping Univ, IFM, S-58183 Linkoping, Sweden Univ Sofia, Fac Phys, Sofia 1164, Bulgaria Aixtron AG, D-52072 Aachen, Germany.
    Evtimova, S
    Linkoping Univ, IFM, S-58183 Linkoping, Sweden Univ Sofia, Fac Phys, Sofia 1164, Bulgaria Aixtron AG, D-52072 Aachen, Germany.
    Persson, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Henry, Anne
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Beccard, R
    Linkoping Univ, IFM, S-58183 Linkoping, Sweden Univ Sofia, Fac Phys, Sofia 1164, Bulgaria Aixtron AG, D-52072 Aachen, Germany.
    Heuken, M
    Linkoping Univ, IFM, S-58183 Linkoping, Sweden Univ Sofia, Fac Phys, Sofia 1164, Bulgaria Aixtron AG, D-52072 Aachen, Germany.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Hydride vapour phase homoepitaxial growth of GaN on MOCVD-grown 'templates'2000Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report on an improved quality of thick HVPE-GaN grown on MOCVD-GaN 'template' layers compared to the material grown directly on sapphire. The film-substrate interface revealed by cathodoluminescence measurements shows an absence of highly doped columnar structures which are typically present in thick HVPE-GaN films grown directly on sapphire. This improved structure results in a reduction of two orders of magnitude of the free carrier concentration from Hall measurements. It was found that the structure, morphology, electrical and optical properties of homoepitaxial thick GaN layers grown by HVPE were strongly influenced by the properties of the MOCVD-GaN 'template'. Additionally the effect of Si doping of the GaN buffer layers on the HVPE-GaN properties was analysed.

  • 288.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Valcheva, E
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Aixtron AG, D-52072 Aachen, Germany.
    Birch, Jens
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Tungasmita, Sukkaneste
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Persson, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Beccard, R
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Aixtron AG, D-52072 Aachen, Germany.
    Heuken, M
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Aixtron AG, D-52072 Aachen, Germany.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Effect of Si doping of metalorganic chemical vapor deposition-GaN templates on the defect arrangement in hydride vapor phase epitaxy-GaN overgrown layers2000Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 88, nr 10, s. 5729-5732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two different types of dislocation arrangements have been observed in hydride vapor-phase epitaxial GaN films grown on sapphire substrates using both undoped and Si-doped GaN templates grown by metalorganic chemical vapor deposition: (i) predominantly straight threading dislocations parallel to the [0001] direction in the layer grown on an undoped template, and (ii) a network of interacting dislocations of edge, screw, and mixed character in the layer grown on a Si-doped template. The two types of defect distribution result in essentially different surface morphologies, respectively: (i) low-angle grain boundaries formed by pure edge dislocations around spiral grown hillocks, and (ii) smooth surface intersected by randomly distributed dislocations. The Si doping of the GaN templates was found to enhance defect interaction in the templates and to enable a reduction of the dislocation density in the overgrown thick GaN films, although it does not lead to an improvement of the overall structural properties of the material. (C) 2000 American Institute of Physics. [S0021-8979(00)08422-X].

  • 289.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Valcheva, E.
    Birch, Jens
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Tungasmita, Sukkaneste
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Persson, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Evtimova, S.
    Faculty of Physics, Sofia University, 5, J. Bourchier blvd., 1164 Sofia, Bulgaria.
    Abrashev, M.
    Faculty of Physics, Sofia University, 5, J. Bourchier blvd., 1164 Sofia, Bulgaria.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Defect and stress relaxation in HVPE-GaN films using high temperature reactively sputtered AlN buffer2001Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 230, nr 3-4, s. 381-386Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of high temperature buffer layers on the structural characteristics of GaN grown by hydride vapour phase epitaxy on sapphire was investigated. Strain relaxation as well as mismatch-induced defect reduction in thick GaN layers grown on AlN buffer was microscopically identified using cathodoluminescence and micro-Raman spectroscopy in cross-section of the films. The results were correlated with photoluminescence and Hall-effect data of layers with different thicknesses. These relaxation processes were suggested to account for the specific defect distribution in the buffers revealed by high-resolution X-ray diffraction and transmission electron microscopy. © 2001 Elsevier Science B.V. All rights reserved.

  • 290.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Valcheva, E
    Linkoping Univ, Dept Phys & Measurement Technol, S-58381 Linkoping, Sweden.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Thick GaN films grown on sapphire: Detects in highly mismatched systems2002Ingår i: Defects and diffusion in semiconductors, ISSN 1012-0386, Vol. 200-2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we review the present knowledge of the defects in thick GaN films grown by hydride vapor phase epitaxy (HVPE) on sapphire substrates. We summarize the defects present in such highly mismatched system into three main categories: large-scale nonuniformities, microstructure crystallographic defects, and point defects. We begin by describing the layer structure typical for thick films grown at very high growth rates, and concentrate on large-scale three-dimensional defects and their impact on the crystal quality. Then we briefly review the current understanding of the variety of extended structural defects with the emphasis on their role in the morphology and relaxation mechanisms in thick heteroepitaxial layers. The discussion is completed by reviewing the point defects in HVPE nitride materials and their influence on the optical properties of GaN films.

  • 291.
    Paskova, Tanja
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Valcheva, E.
    Paskov, Plamen
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Roskowski, A.M.
    Dept of Mat Science and Engineering, North Carolina State University, Raleigh, NC 27695-7919, United States.
    Davis, R.F.
    Dept of Mat Science and Engineering, North Carolina State University, Raleigh, NC 27695-7919, United States.
    Beaumont, B.
    2720 Clemin Saint Bernard, Vallauris F-06220, France.
    Gibart, P.
    2720 Clemin Saint Bernard, Vallauris F-06220, France.
    HVPE-GaN: Comparison of emission properties and microstructure of films grown on different laterally overgrown templates2004Ingår i: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 13, nr 4-8, s. 1125-1129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on a comparative study of defect and emission distributions in thick hydride vapor phase epitaxial (HVPE) GaN films grown on two different patterned template structures separately produced by multi-step procedures using metalorganic vapor phase epitaxy (MOVPE). The observed differences in the microstructures and emission distributions at the early stages of the growth in both cases were related to the change of the dominating growth mode sequence and point defects incorporation. Both template structures were found to favor formation of voids in the coalescence regions, which leads to a partial strain relaxation and allows overgrowth of thicker films without cracks. © 2003 Elsevier B.V. All rights reserved.

  • 292.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    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
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    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 epitaxy2001Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 228, nr 2, s. 485-488Artikel i tidskrift (Refereegranskat)
    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.

  • 293.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Iwaya, M
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Nitta, S
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Amano, H
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Akasaki, I
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy with mass transport2000Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 77, nr 11, s. 1638-1640Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on studies of In0.12Ga0.88N/GaN heterostructures with three 35-Angstrom-thick quantum wells (QWs) grown on sapphire substrates by metalorganic vapor phase epitaxy with employment of mass transport. The structure is demonstrated to show good structural and optical properties. The threading dislocation density is less than 10(7) cm(-2) for the mass-transport regions. The photoluminescence (PL) spectrum is dominated by the rather narrow near-band gap emission at 2.97 eV with a linewidth of 40 meV. This emission has a typical PL decay time about 5 ns at 2 K within the PL contour. With increasing excitation intensity, an additional transition with longer decay time (about 200 ns) is enhanced at energy about 2.85 eV. The position of this line depends strongly on the excitation power. We explain the data in terms of a model, where the PL is a result of contribution from at least two nonequivalent QWs, which could be realized due to a potential gradient across the layers. (C) 2000 American Institute of Physics. [S0003- 6951(00)04337-0].

  • 294.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Iwaya, M
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Nitta, S
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Amano, H
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Akasaki, I
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Luminescence of InGaN/GaN multiple quantum wells grown by mass-transport2001Ingår i: Materials Science Forum, Vols. 353-356, 2001, Vol. 353-3, s. 791-794Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present an optical study of an In0.12Ga0.88N/GaN structure containing three quantum wells (QW) grown by metalorganic vapor phase epitaxy using mass transport. The mass-transport regions demonstrate a high structural quality with a threading dislocation density less than 10(7) cm(-2). The photoluminescence (PL) spectrum is dominated by a 40 meV - narrow line centered at 2.97 eV at 2 K. This emission has a typical PL decay time about 5 ns at 2 K within the PL contour. An additional line with longer decay time (about 200 ns) is observed at an energy of similar to2.85 eV. The position of this line shifts towards higher energies with increasing excitation power. The data are explained in terms of a model, where the PL originates from two nonequivalent quantum wells, which could be realized due to a potential gradient across the layers.

  • 295.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Kamiyama, S
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Iwaya, M
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Amano, H
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Akasaki, I
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Optical study of AlGaN/GaN multiple quantum well structures grown on laterally overgrown GaN templates2002Ingår i: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 190, nr 1, s. 107-111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on optical studies of Al0.1Ga0.9N/GaN structures with five 30 (A) over circle thick GaN quantum wells (QWs) grown by metal organic vapor phase epitaxy using the lateral overgrowth technique. Overgrown regions demonstrate better structural and optical properties. The low temperature photoluminescence (PL) is dominated by the multiple quantum well (MQW) emission at 3.53 eV with the linewidth of similar to50 meV. The PL decay time for this line was measured to be similar to600 ps. Comparison with an AlGaN/GaN MQW light-emitting diode (LED) structure is done. The LED structure was grown with a p-type doped AlGaN top layer and a p-GaN contact layer. The PL spectrum of the LED structure shows besides the donor-acceptor pair recombination from the top layer an additional 60 meV wide line at 3.64 eV. The presence of two MQW peaks may be related to the potential gradient present across the MOW structure.

  • 296.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Takeuchi, T
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Amano, H
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Akasaki, I
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Origin of multiple peak photoluminescence in InGaN/GaN multiple quantum wells2000Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 88, nr 5, s. 2677-2681Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optical spectroscopy has been performed for a set of In0.12Ga0.88N/GaN multiple quantum wells (MQW) grown by metalorganic vapor phase epitaxy at 820 degrees C. Time-resolved, temperature- and power-dependent photoluminescence as well as spatially-resolved cathodoluminescence measurements have been applied to elucidate the nature of the recombination mechanisms responsible for the radiative transitions in the samples. The photoluminescence spectra in this set of samples are dominated by strong multiple peak emissions associating with both confined levels of the MQW system (the higher energy band) and with strongly localized states of energies much lower than the QW band gap. We suggest that the photoluminescence originate from (i) the MQW exciton recombination, (ii) excitons localized in the quasidot regions with indium concentrations higher than in the alloy due to segregation processes, and (iii) from localized states in zero-dimensional quantum islands created by surface defects such as pits and V defects. Buried side-wall quantum wells caused by V defects might also influence the photoluminescence spectra. (C) 2000 American Institute of Physics. [S0021-8979(00)00117-1].

  • 297.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Yamaguchi, S
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Amano, H
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Akasaki, I
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Meijo Univ, Dept Elect Engn & Elect, Tempaku Ku, Nagoya, Aichi 4688502, Japan Meijo Univ, High Tech Res Ctr, Tempaku Ku, Nagoya, Aichi 4688502, Japan.
    Optical spectroscopy of GaN grown by metalorganic vapor phase epitaxy using indium surfactant2000Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 76, nr 23, s. 3388-3390Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of In surfactant during metalorganic vapor phase epitaxial growth on sapphire substructure on the properties of GaN layers is studied using time-resolved photoluminescence. cathodoluminescence. and scanning electron microscopy. The samples are divided into two groups. where hydrogen and nitrogen, respectively, have been used as a carrier gas during growth. It is shown that In-doped samples have a lower dislocation density, a narrower photoluminescence linewidth, and a longer foe exciton lifetime. The influence of indium is stronger for GaN layers grown in nitrogen-rich conditions. The improvements of structural and optical properties are attributed to the effect of In on dislocations. (C) 2000 American Institute of Physics. [S0003-6951(00)02723-6].

  • 298.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Paskova, Tanja
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bound exciton dynamics in GaN grown by hydride vapor-phase epitaxy1999Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 75, nr 26, s. 4124-4126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temperature-dependent time-resolved photoluminescence measurements were performed on thick GaN layers grown by hydride vapor-phase epitaxy on Al2O3 substrates. Radiative lifetimes were determined for the neutral-donor-bound exciton with position at 3.478 eV and for two neutral-acceptor-bound excitons at 3.473 and 3.461 eV. We report a value of 3600 ps for the radiative lifetime of the acceptor-bound exciton transition at 3.461 eV. The dominant mechanism responsible for the nonradiative recombination of the bound excitons is shown to be connected with dissociation of the bound excitons into free excitons. (C) 1999 American Institute of Physics. [S0003-6951(99)00752-4].

  • 299.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, Peder
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Iwaya, M.
    Department of Electrical Engineering and Electronics and High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Nitta, S.
    Department of Electrical Engineering and Electronics and High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Amano, H.
    Department of Electrical Engineering and Electronics and High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Akasaki, I.
    Department of Electrical Engineering and Electronics and High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Photoluminescence of InGaN/GaN multiple quantum wells grown by mass transport2001Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 230, nr 3-4, s. 473-476Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on studies of an In0.12Ga0.88N/GaN structure with three 35 Å thick quantum wells (QWs) grown by metalorganic vapor phase epitaxy with employment of mass transport. The mass-transport regions demonstrate a threading dislocation density less than 107 cm-2. The photoluminescence (PL) spectrum is dominated by a 40 meV-narrow line centered at 2.97 eV at 2 K. This emission has a typical PL decay time of about 5 ns at 2 K within the PL contour. An additional line with longer decay time (about 200 ns) is observed at an energy about 2.85 eV. The position of this line shifts towards higher energies with increasing excitation power. The data are consistent with a model, where the PL originates from at least two nonequivalent QWs, which could be realized due to a potential gradient across the layers. © 2001 Elsevier Science B.V. All rights reserved.

  • 300.
    Pozina, Galia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bergman, Peder
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Yamaguchi, S.
    Department of Electrical Engineering and Electronics, High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Amano, H.
    Department of Electrical Engineering and Electronics, High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Akasaki, I.
    Department of Electrical Engineering and Electronics, High-Tech Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan.
    Time-resolved optical properties of GaN grown by metalorganic vapor phase epitaxy with indium surfactant2001Ingår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 82, nr 1-3, s. 137-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of isoelectronic indium doping on optical properties of GaN layers grown by metalorganic vapor-phase epitaxy have been studied. Two sets of samples have been grown with hydrogen and with nitrogen as carrier gas. It has been shown from scanning electron microscopy, cathodoluminescence and time-resolved photoluminescence that In-doped samples have a lower dislocation density, a narrower photoluminescence line width and a longer free exciton lifetime. The improvements of structural and optical properties are attributed to the effect of In on dislocations. © 2001 Elsevier Science B.V.

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