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  • 1.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Edwards, N. V.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Lindström, J. L.
    Bremser, M. D.
    Davis, R. F.
    Amano, H.
    Akasaki, I.
    Electronic structure of the 0.88-eV luminescence center in electron-irradiated gallium nitride1999In: Physical review. B, Condensed matter and materials physics, Vol. 60, no 3, p. 1746-1751Article in journal (Refereed)
    Abstract [en]

     Photoluminescence (PL) spectroscopy is employed to determine the nature of a near-infrared PL emission with a no-phonon line at ∼0.88 eV, commonly present in electron-irradiated GaN. This PL emission is suggested to originate from an internal transition between a moderately shallow excited state (with an ionization energy ∼21 meV) and the deep ground state (with an ionization energy ∼900 meV) of a deep defect. The existence of a higher-lying second excited state related to the 0.88-eV PL center is also shown from temperature-dependent studies. A different electronic character of the wave functions related to the first and second excited states has been revealed by PL polarization measurements. Since the PL emission has been observed with comparable intensity in all electron-irradiated GaN samples independent of doping on the starting material, it is proposed that either native defects, or common residual contaminants or their complexes are involved. The substitutional ON donor (or related complex) is considered as the most probable candidate, based on the observed striking similarity in the local vibrational properties between the 0.88-eV PL centers and the substitutional OP donor in GaP.

  • 2.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    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, Materials Science .
    Lindström, J. L.
    Amano, H.
    Akasaki, I.
    Photoluminescence Spectroscopy of the 0.88 eV Emission in Electron-Irradiated GaN1999In: APS March Meeting,1999, 1999Conference paper (Other academic)
  • 3.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    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, Materials Science .
    Lindström, J. L.
    Amano, H.
    Aksaki, I.
    Effect of electron irradiation on optical properties of gallium nitride1999In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T79, p. 72-75Article in journal (Refereed)
    Abstract [en]

     The effect of electron irradiation on the optical properties of GaN epilayers is studied in detail by photoluminescence (PL) spectroscopy. The most common types of GaN material are used, i.e. strained heteroepitaxial layers grown on 6H SiC or Al2O3 substrates, and thick bulk-like layers with the conductivity varying from n-type to semi-insulating and p-type. The main effects of electron irradiation on all investigated samples are found to be as follows: (i) a radiation-induced quenching of excitonic emissions in the near band gap region; (ii) an appearance of broad overlapping PL emissions within the spectral range 0.7-1.1 eV and (iii) the appearance of a PL band with a sharp no-phonon (NP) line at around 0.88 eV followed by a rich phonon assisted sideband. The 0.88 eV band is shown to originate from an internal transition of a deep defect. With increasing temperature a hot PL line can be observed at about 2-4 meV above the NP line, originating from higher lying excited states of the defect. The electronic structure of the 0.88 eV defect is shown to be very sensitive to the internal strain field in the GaN epilayers.

  • 4.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Sörman, E.
    Hai, P. N.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    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.
    Magneto-optical spectroscopy of defects in wide bandgap semiconductors: GaN and SiC2000In: Proceedings Conference on Optoelectronic and Microelectronic Materials and Devices, IEEE , 2000, p. 497-502Conference paper (Refereed)
    Abstract [en]

    We review recent progress in our understanding of intrinsic defects in GaN and SiC, gained from magneto-optical studies by Zeeman measurements and optically detected magnetic resonance. The two best-known intrinsic defects in these two wide bandgap semiconductors, i.e. the Ga interstitial in GaN and the silicon vacancy in SiC, are discussed in detail. The Ga interstitial is the first and only intrinsic defect in GaN that has so far been unambiguously identified, either in the presumably isolated form or in a family of up to three complexes. The silicon vacancy is among the most studied intrinsic defect in SiC, at least in two charge states, and yet still remains controversial.

  • 5.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wagner, Matthias
    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 .
    Lindström, J. L.
    Amano, H.
    Akasaki, I.
    Role of the Substitutional Oxygen Donor in the Residual n-type Conductivity in GaN1999Conference paper (Refereed)
    Abstract [en]

     A detailed photoluminescence (PL) study reveals a striking similarity in local vibrational properties of a defect center in GaN as compared to that for the substitutional OP donor in GaP. This observation could be interpreted as if the center is in fact related to the substitutional oxygen donor in GaN. The deep-level nature experimentally determined for the defect center calls for caution of a commonly referred model that the substitutional oxygen donor is responsible for the residual n-type conductivity in GaN.

  • 6.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hai, P. N.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Buyanova, Irina
    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, Materials Science .
    Amano, H.
    Akasaki, I.
    Xin, H. P.
    Tu, C. W.
    Optical and Microwave Double Resonance of III-nitrides1999In: Joint International Meeting the 196th Meeting of The Electrochemical Society ECS and the 1999 Fall Meeting of The Electrochemical Society of Japan ECSJ,1999, 1999, p. 764-Conference paper (Other academic)
    Abstract [en]

      

  • 7.
    Magnusson, Björn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Vanadium-related center in 4H silicon carbide2000In: Materials Science Forum, Vols. 338-343, 2000, Vol. 338-342, p. 631-634Conference paper (Refereed)
    Abstract [en]

    The V4+ (3d(1)) center in 4H SiC is investigated using photoluminescence (PL) and photoluminescence excitation (PLE). The energy position of the ground state of the defect is determined to be 2.1 +/- 0.1 eV below the conduction band for both the hexagonal and the quasi-cubic site. A broad peak in the PLE spectrum is tentatively ascribed to the excited A(1) state, previously believed to be located in the conduction band.

  • 8.
    Monemar, Bo
    et al.
    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.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    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.
    Wagner, Matthias
    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.
    Defects in Gallium Nitride1999In: International Workshop on Materials Science,1999, Proc. of the International Workshop on Materials Science 99, ed. by F. F. Bekker et al., Vol. 1: Hanoi National University Publishing House , 1999, p. 28-Conference paper (Refereed)
  • 9.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hai, P. N.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Ellison, A.
    Hallin, Christer
    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 .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Optically detected magnetic resonance studies of intrinsic defects in 6H-SiC1999In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 14, no 12, p. 1141-1146Article in journal (Refereed)
    Abstract [en]

     Optically detected magnetic resonance (ODMR) was used for study of defects in n-type 6H-SiC. Four ODMR spectra related to spin S = 1 centres were observed. Two of these centres, labelled a and b, have a trigonal symmetry with the symmetry axis along the c-axis of the hexagonal crystal. For the other two centres, labelled c and d, the symmetry is lower (C1h) and the principal axis z of the g- and D-tensor is about 71 degrees off the c-axis. Based on the symmetry axes, the annealing behaviour and the intensity, these spectra are suggested to originate from different configurations of the paired centre between a silicon vacancy and a nearest-neighbour point defect (either a carbon vacancy or a silicon antisite), occupying different inequivalent sites in the 6H-SiC. These defects are non-radiative and act as efficient recombination channels in the material.

  • 10.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hemmingsson, Carl
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Storasta, Liutauras
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    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.
    Greulich-Weber, S.
    Spaeth, J.-M.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Electronic structure of deep defects in SiC2004In: Silicon Carbide: Recent Major Advances / [ed] W.J. Choyke, H. Matsunami, G. Pens, Berlin, Heidelberg: Springer Verlag , 2004, p. -899Chapter in book (Other academic)
    Abstract [en]

    Since the 1997 publication of Silicon Carbide - A Review of Fundamental Questions and Applications to Current Device Technology edited by Choyke, et al., there has been impressive progress in both the fundamental and developmental aspects of the SiC field. So there is a growing need to update the scientific community on the important events in research and development since then. The editors have again gathered an outstanding team of the world's leading SiC researchers and design engineers to write on the most recent developments in SiC. The book is divided into five main categories: theory, crystal growth, characterization, processing and devices. Every attempt has been made to make the articles as up-to-date as possible and assure the highest standards of accuracy. As was the case for earlier SiC books, many of the articles will be relevant a decade from now so that this book will take its place next to the earlier work as a permanent and essential reference volume.

  • 11. Toropov, A. A.
    et al.
    Sorokin, S. V.
    Kuritsyn, K. A.
    Ivanov, S. V.
    Kopev, P. S.
    Reuscher, G.
    Waag, A.
    Landwehr, G.
    Wagner, Matthias
    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.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnetooptical studies of CdSe/(Zn,Mn)Se semimagnetic nanostructures2000In: 8th International Symposium Nanostructures: Physics Technology,2000, Ft. Belvoir Defense Technical Information Center , 2000, p. 440-443Conference paper (Refereed)
    Abstract [en]

    In conclusion the performed magneto-PL measurements exhibit fonrmation of 0D excitons in CdSe/(Zn,Mn)Se nanostructures. The excitonic states forming the inhomogeneously broadened emission band differ both in their energy (due to fluctuations in the sizes and compositions among the localization sites) and in magnetic properties (most probably, due to the effect of Mn ions clustering in the nearby regions). The structure potential for spin-related optoelectronic applications is demonstrated, owing to almost complete circular polarization of the emitted light within the wide spectral range (about 1OO meV) at moderate magnetic fields.

  • 12. Toropov, A. A.
    et al.
    Sorokin, S. V.
    Kuritsyn, K. A.
    Ivanov, S. V.
    Pozina, Galia
    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 .
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    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, Materials Science .
    Waag, A.
    Yakovlev, D. R.
    Sas, C.
    Ossau, W.
    Landwehr, G.
    Magneto-photoluminescence studies of Cd(Mn)Se/Zn(Mn)Se diluted magnetic nanostructures2001In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 10, no 1-3, p. 362-367Article in journal (Refereed)
    Abstract [en]

    We report on cw and time-resolved photoluminescence (PL) studies of Cd(Mn)Se/Zn(Mn)Se diluted magnetic semiconductor nanostructures grown by molecular beam epitaxy. Excitonic PL intensity, decay time and Zeeman splitting have been studied systematically as a function of Cd(Mn)Se nominal thickness, Mn concentration and sample design. Wave function mapping has been performed, evidencing the formation of semi-magnetic quantum disk islands in the samples with thick enough Cd(Mn)Se insertions. ⌐ 2001 Elsevier Science B.V.

  • 13.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    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.
    Lindström, J. L.
    Amano, H.
    Akasaki, I.
    Internal transitions of a deep level defect in GaN studied by photoluminescence and optically detected magnetic resonance1999In: 24th International Conference on the Physics of Semiconductors,1998, Proc. of the 24th International Conference on the Physics of Semiconductors, ed. by D. Gershoni: World Scientific, Singapore , 1999, p. IX B 3-Conference paper (Other academic)
  • 14.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    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.
    Lindström, J. L.
    Amano, H.
    Akasaki, I.
    Magnetooptical investigations on electron irradiated GaN1999In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T79, p. 53-55Article in journal (Refereed)
    Abstract [en]

    Optically Detected Magnetic Resonance (ODMR) and Level Anti-Crossing (LAC) experiments are employed to characterize the properties of two photoluminescence bands at 0.93 eV and 0.875 eV observable in electron irradiated GaN. Only one almost isotropic ODMR line and no LAC feature appear when monitoring the 0.93 eV emission, whereas two ODMR and two LAC signals can be found connected to the 0.875 eV band from spectral dependence studies. One possible explanation for the recombination leading to the 0.875 eV emission is a transition between excited states and ground state of a deep donor, where the ODMR signals arise from microwave induced transitions within the manifold of excited states. Within this manifold avoided crossings of the magnetic sublevels give rise to the observed LAC signals.

  • 15.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Thinh, N. Q.
    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.
    Lindström, J. L.
    Amano, H.
    Akasaki, I.
    Magneto-optical studies of the 0.88-eV photoluminescence emission in electron-irradiated GaN2000In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 62, no 24, p. 16572-16577Article in journal (Refereed)
    Abstract [en]

    Properties of the 0.88-eV photoluminescence (PL) in electron-irradiated wurtzite GaN have been investigated in detail by a combination of various magneto-optical techniques, including Zeeman measurements of PL, optically detected magnetic resonance (ODMR), and level anticrossing (LAC). ODMR observed by monitoring the PL emission is demonstrated to originate from a spin triplet. The symmetry of the corresponding defect is shown to be rhombic with its principal axes pointing into the high-symmetry directions Z=[0001], Y=[11¯00], and X=[112¯0]. From the Zeeman measurements the emission is shown to arise from an optical transition between a singlet excited state and the singlet ground state, providing convincing evidence for indirect detection of the spin triplet ODMR. LAC investigations of the same PL emission reveal two LAC lines, among which one is related to the spin triplet detected in ODMR.

  • 16.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Storasta, Liutauras
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, JP
    Magnusson, Björn
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Photoluminescence up-conversion processes in SiC2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 309-312Conference paper (Refereed)
    Abstract [en]

    Efficient photoluminescence up-conversion is observed in 4H SiC samples containing both the UD-3 defect with its characteristic photoluminescence (PL) no-phonon (NP) line in the near infrared at 1.356 eV and the titanium impurity with its emission in the visible spectral region. When both defects are present, the titanium emission can be excited efficiently by tuning the laser to UD-3. In 4H samples containing either only UD-3 or only titanium, a different photoluminescence up-conversion process can be observed. This second process occurs at photon energies higher than approximately 1.5 eV without exhibiting a clear threshold. In 6H and 15R SiC only this second process was found, even when both the UD-3 defect and the titanium impurity are abundant.

  • 17.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Storasta, Liutauras
    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 .
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Photoluminescence upconversion in 4H-SiC2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 14, p. 2547-Article in journal (Refereed)
    Abstract [en]

     Efficient photoluminescence upconversion is observed in 4H-SiC samples containing both the UD-3 defect and the titanium impurity. In this process, the titanium photoluminescence emission with no-phonon (NP) lines at 2.848 eV (A0) and 2.789 eV (B0) can be excited by tuning the laser to the NP line of UD-3 at 1.356 eV. In samples containing either only UD-3 or only titanium, a different photoluminescence upconversion process can be observed, which occurs at photon energies higher than ~1.5 eV without exhibiting sharp features. At least one of the two processes generates both free electrons and free holes and can, therefore, be a candidate for an important recombination channel.

  • 18.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Electronic structure of the UD3 defect in 4H and 6H SiC2002In: Materials Science Forum, Vols. 389 - 393, Trans Tech Publications, Switzerland , 2002, p. 509-Conference paper (Refereed)
  • 19.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    UD-3 defect in 4H, 6H, and 15R SiC: Electronic structure and phonon coupling2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 11Article in journal (Refereed)
    Abstract [en]

    The UD-3 photoluminescence (PL) spectrum is observed in high-resistive or semi-insulating bulk 4H, 6H, and 15R SiC. It consists of one no-phonon (NP) line in 4H and 6H SiC and two NP lines in 15R SiC. The line positions are 1.3555 eV in 4H SiC, 1.3440 eV in 6H SiC and 1.3474 eV (UD-3(L)) and 1.3510 eV (UD-3(H)) in 15R SiC. In PL excitation experiments, an additional set of four lines (UD-3(I)-UD-3(IV)) is observed in all three polytypes. The symmetry of the ground state and the excited states involved in these transitions is determined from Zeeman and polarization experiments. The NP line is accompanied by a broad phonon assisted side band. In addition, three sharp transitions UD-3(a), UD-3(b), and UD-3(c) and three broader features have been observed. These are assigned to local phonons.

  • 20.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Sörman, E.
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lindström, J. L.
    Electronic structure of the neutral silicon vacancy in 4H and 6H SiC2000In: Physical review. B, Condensed matter and materials physics, ISSN 2469-9950, Vol. 62, no 24, p. 16555-16560Article in journal (Refereed)
    Abstract [en]

     Detailed information about the electronic structure of the lowest-lying excited states and the ground state of the neutral silicon vacancy in 4H and 6H SiC has been obtained by high-resolution photoluminescence (PL), PL excitation (PLE), and Zeeman spectroscopy of both PL and PLE. The excited states and the ground states involved in the characteristic luminescence of the defect with no-phonon (NP) lines at 1.438 and 1.352 eV in 4H SiC and 1.433, 1.398, and 1.368 eV in 6H SiC are shown to be singlets. The orbital degeneracy of the excited states is lifted by the crystal field for the highest-lying NP lines corresponding to one of the inequivalent lattice sites in both polytypes, leading to the appearance of hot lines at slightly higher energies. Polarization studies of the NP lines show a different behavior for the inequivalent sites. A comparison of this behavior in the two polytypes together with parameters from spin resonance studies provides useful hints for the assignment of the no-phonon lines to the inequivalent sites. In strained samples an additional fine structure of the NP lines can be resolved. This splitting may be due to strain variations in the samples.

  • 21.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Sörman, E.
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lindström, J. L.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Zeeman spectroscopy of the neutral silicon vacancy in 6H and 4H SiC1999In: Physica B. Vol. 273-274, Elsevier , 1999, p. 663-Conference paper (Refereed)
    Abstract [en]

    High-resolution photoluminescence (PL) and PL excitation (PLE) spectroscopy has been employed to reveal the electronic structure of the neutral silicon vacancy in 6H and 4H SiC. The defect gives rise to characteristic PL emissions with three no-phonon lines in 6H SiC and two in 4H SiC at around 1.4 eV. All of the no-phonon lines are shown to arise from transitions between singlet (S=0) excited states and singlet ground states. Nevertheless, optically detected magnetic resonance (ODMR) signals typical for a spin triplet (S=1) configuration can be obtained when monitoring the emission under resonant excitation. This observation can be explained by non-radiative recombination via a lower lying excited triplet state. In strained samples all no-phonon PL lines are split into a series of lines. For the highest energy lines the main splitting can be attributed to lifting of the orbital degeneracy of the excited states, the additional broadening or splitting is probably due to a strain distribution in the samples.

  • 22.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Sörman, E.
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lindström, J. L.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Properties of the neutral silicon vacancy in 6H SiC1999Conference paper (Other academic)
    Abstract [en]

      

  • 23.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Thinh, NQ
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Baranov, PG
    Mokhov, EN
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lindstrom, JL
    Ligand hyperfine interaction at the neutral silicon vacancy in 4H- and 6H-SiC2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 15Article in journal (Refereed)
    Abstract [en]

    The silicon vacancy in its neutral charge state (V-Si) has been unambiguously identified in 4H- and 6H-SiC. This was achieved by observation of ligand hyperfine interaction with the four carbon atoms in the nearest-neighbor shell and the twelve silicon atoms in the next-nearest-neighbor shell surrounding the vacancy. The complete hyperfine tensors have been determined for the V-Si(0) center residing at all inequivalent lattice sites in the two polytypes. These are compared with the parameters previously obtained for the negatively charged silicon vacancy.

  • 24.
    Wagner, Matthias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Thinh, NQ
    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.
    Baranov, PG
    Mokhov, EN
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    The neutral silicon vacancy in SiC: Ligand hyperfine interaction2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 501-504Conference paper (Refereed)
    Abstract [en]

    The isolated silicon vacancy in its neutral charge state has unambiguously been confirmed in electron irradiated 4H and 6H SiC. This was achieved by the observation of the ligand hyperfine lines arising from interaction with C-13 atoms in the nearest-neighbor (NN) shell and With Si-29 atoms in the next-nearest-neighbor (NNN) shell in optically detected magnetic resonance (ODMR) experiments. The complete hyperfine tensors for all inequivalent lattice sites have been deduced and are compared to the known hyperfine parameters for the negatively charged silicon vacancy in the two polytypes.

1 - 24 of 24
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