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  • 1. Aavikko, R.
    et al.
    Saarinen, K.
    Magnusson, Björn
    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.
    Clustering of Vacancies in Semi-Insulating SiC Observed with Positron Spectroscopy2006In: Materials Science Forum, Vols. 527-529, 2006, Vol. 527-529, p. 575-578Conference paper (Refereed)
  • 2. Aavikko, R
    et al.
    Saarinen, K
    Magnusson, Björn
    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.
    Observation of vacancy clusters in HTCVD grown SiC2005In: Materials Science Forum, Vols. 483-485, 2005, Vol. 483, p. 469-472Conference paper (Refereed)
    Abstract [en]

    Positron lifetime spectroscopy was used to study defects in semi-insulating (SI) silicon carbide (SiC) substrates grown by high-temperature chemical vapor deposition (HTCVD). The measured positron lifetime spectra can be decomposed into two components, of which the longer corresponds to vacancy clusters. We have carried out atomic superposition calculations to estimate the size of these clusters.

  • 3. Aavikko, R.
    et al.
    Saarinen, K.
    Tuomisto, F.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Clustering of vacancy defects in high-purity semi-insulating SiC2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 8, p. 085208-Article in journal (Refereed)
    Abstract [en]

    Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material is shown to contain (i) vacancy clusters consisting of four to five missing atoms and (ii) Si-vacancy-related negatively charged defects. The total open volume bound to the clusters anticorrelates with the electrical resistivity in both as-grown and annealed materials. Our results suggest that Si-vacancy-related complexes electrically compensate the as-grown material, but migrate to increase the size of the clusters during annealing, leading to loss of resistivity. © 2007 The American Physical Society.

  • 4. Arnaudov, B.
    et al.
    Paskova, Tanja
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lu, H.
    Schaff, W.J.
    On the nature of the near bandedge luminescence of InN epitaxial layers2005In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 772, p. 285-286Article in journal (Refereed)
  • 5. Arnaudov, B
    et al.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Valcheva, E
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Lu, H
    Schaff, WJ
    Amano, H
    Akasaki, I
    Energy position of near-band-edge emission spectra of InN epitaxial layers with different doping levels2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 11Article in journal (Refereed)
    Abstract [en]

    We studied the shape and energy position of near-band-edge photoluminescence spectra of InN epitaxial layers with different doping levels. We found that the experimental spectra of InN layers with moderate doping level can be nicely interpreted in the frames of the "free-to-bound" recombination model in degenerate semiconductors. For carrier concentrations above n>5x10(18) cm(-3) the emission spectra can also be modeled satisfactorily, but a contribution due to a pushing up of nonequilibrium holes over the thermal delocalization level in the valence band tails should be considered in the model. The emission spectra of samples with low doping level were instead explained as a recombination from the bottom of the conduction band to a shallow acceptor assuming the same value of the acceptor binding energy estimated from the spectra of highly doped samples. Analyzing the shape and energy position of the free-electron recombination spectra we determined the carrier concentrations responsible for the emissions and found that the fundamental band gap energy of InN is E-g=692+/-2 meV for an effective mass at the conduction-band minimum m(n0)=0.042m(0).

  • 6.
    Arnaudov, B.
    et al.
    Faculty of Physics, Sofia University, 5 J. Bourchier Blvd, 1164 Sofia, Bulgaria.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Valcheva, E.
    Faculty of Physics, Sofia University, 5 J. Bourchier Blvd, 1164 Sofia, Bulgaria.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Lu, H.
    Department of Electrical Engineering, Cornell University, Ithaka, NY 14583, United States.
    Schaff, W.J.
    Department of Electrical Engineering, Cornell University, Ithaka, NY 14583, United States.
    Amano, H.
    Department of Electrical Engineering, Meijo University, I-501 Shiogamaguchi, Tempaku-ku, Nagoia 468, Japan.
    Akasaki, I.
    Department of Electrical Engineering, Meijo University, I-501 Shiogamaguchi, Tempaku-ku, Nagoia 468, Japan.
    Free-to-bound radiative recombination in highly conducting InN epitaxial layers2004In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 36, no 4-6, p. 563-571Article in journal (Refereed)
    Abstract [en]

    We present a theoretical simulation of near-band-edge emission spectra of highly conducting n-InN assuming the model of 'free-to-bound' radiative recombination (FBRR) of degenerate electrons from the conduction band with nonequilibrium holes located in the valence band tails. We also study experimental photoluminescence (PL) spectra of highly conducting InN epitaxial layers grown by MBE and MOVPE with electron concentrations in the range (7.7 × 1017-6 × 1018) cm-3 and find that the energy positions and shape of the spectra depend on the impurity concentration. By modeling the experimental PL spectra of the InN layers we show that spectra can be nicely interpreted in the framework of the FBRR model with specific peculiarities for different doping levels. Analyzing simultaneously the shape and energy position of the InN emission spectra we determine the fundamental bandgap energy of InN to vary between Eg = 692 meV for effective mass mn0 = 0.042m0 and Eg =710 meV for mn0 = 0.1m0. © 2004 Elsevier Ltd. All rights reserved.

  • 7.
    Bergman, JP
    et al.
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden ABB Corp, SE-72178 Vasteras, Sweden Okmet AB, SE-58183 Linkoping, Sweden.
    Jakobsson, H
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden ABB Corp, SE-72178 Vasteras, Sweden Okmet AB, SE-58183 Linkoping, Sweden.
    Storasta, Liutauras
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Carlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Sridhara, S
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden ABB Corp, SE-72178 Vasteras, Sweden Okmet AB, SE-58183 Linkoping, Sweden.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lendenmann, H
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden ABB Corp, SE-72178 Vasteras, Sweden Okmet AB, SE-58183 Linkoping, Sweden.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Characterisation and defects in silicon carbide2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3Conference paper (Refereed)
    Abstract [en]

    In this work we present experimental results of several defects in 4H Sic that are of interest both from a fundamental and physical point of view. And also of great importance for device applications utilizing the Sic material. These defects include the temperature stable so called D1 defect, which is created after irradiation. This optical emission has been identified as an isoelectronic defect bound at a hole attractive pseudodonor, and we have been able to correlate this to the electrically observed hole trap HS1 seen in minority carrier transient spectroscopy (MCTS). It also includes the UD1 defect observed using absorption and FTIR and which is believed to be responsible for the semi-insulating behavior of material grown by the High temperature, HTCVD technique. Finally, we have described the formation and proper-ties of critical, generated defect in high power Sic bipolar devices. This is identified as a stacking fault in the Sic basal plane, using mainly white beam synchrotron Xray topography. The stacking fault is both optically and electrically active, by forming extended local potential reduction of the conduction band.

  • 8.
    Bergman, Peder
    et al.
    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.
    Carlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Sridhara, S.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Defects in 4H silicon carbide2001In: Physica B, Vols. 308-310, 2001, Vol. 308-310, p. 675-679Conference paper (Refereed)
    Abstract [en]

    We present experimental results related to several different intrinsic defects that in different ways influence the material properties and are therefore technologically important defects. This includes the so-called D1 defect which is created after irradiation and which is temperature stable. From the optical measurements we were able to identify the D1 bound exciton as an isoelectronic defect bound at a hole attractive pseudo-donor, and we have been able to correlate this to the electrically observed hole trap HS1 seen in minority carrier transient spectroscopy (MCTS). Finally, we describe the formation and properties of a critical, generated defect in high power SiC bipolar devices. It is identified as a stacking fault in the SiC basal plane. It can be seen as a local reduction of the carrier lifetime, in triangular or rectangular shape, which explains the enhanced forward voltage drop in the diodes. The entire stacking faults are also optically active as can be seen as dark triangles and rectangles in low temperature cathodo-luminescence, and the fault and their bounding partial dislocations are seen and identified using synchrotron topography. © 2001 Elsevier Science B.V. All rights reserved.

  • 9.
    Carlsson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    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.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Skold, K
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Uppsala Univ, Inst Neutron Res, SE-61182 Nykoping, Sweden.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Neutron irradiation of 4H SiC2001In: Materials Science Forum, Vols. 353-356, 2001, Vol. 353-3, p. 555-558Conference paper (Refereed)
    Abstract [en]

    The effect of neutron irradiation on 4H SiC epitaxial layers are studied. Several different doses of both fast and thermal neutrons have been used and the samples have been annealed from 500 degreesC to 2000 degreesC. The defect concentration dependence on the fast neutron flux and on the annealing temperature is investigated. At temperatures from 900 degreesC to 1300 degreesC new lines between 3960 Angstrom and 4270 Angstrom appear. They are similar in behavior to the E-A and D1 spectra and are assumed to be related to excitons bound to isoelectronic centers. After annealing at 2000 degreesC another new line appears at 3809 Angstrom. The similarity of this line with phosphorus in 6H makes us tentatively ascribe it to phosphorus.

  • 10.
    Carlsson, Patrick
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Nguyen, Son Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Norstel AB, Ramshällsvägen 15, SE-602 38 Norrköping, Sweden.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Intrinsic Defects in HPSI 6H-SiC: an EPR Study2009In: Materials Science Forum, Vols. 600-603, Trans Tech Publications , 2009, p. 381-384Conference paper (Refereed)
    Abstract [en]

    High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects. The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV above the valence band. The thermal activation energies as determined from the temperature dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of the intrinsic defects and the stability of the SI properties were studied up to 1600°C.

  • 11.
    Carlsson, Patrick
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Isoya, J.
    University of Tsukuba.
    Morishita, N.
    Japan Atomic Energy Agency.
    Ohshima, T.
    Japan Atomic Energy Agency.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    The EI4 EPR centre in 6H SiC2010In: Physica Scripta, Vol. T141, IOP Publishing , 2010, p. 014013-Conference paper (Refereed)
    Abstract [en]

    We present the results of our recent electron paramagnetic resonance (EPR) studies of the EI4 EPR centre in electron-irradiated high-purity semi-insulating 6H SiC. Higher signal intensities and better resolution compared with previous studies have enabled a more detailed study of the hyperfine (hf) structure. Based on the observed hf structure due to the interaction with Si and C neighbours, the effective spin S = 1, the C-1h-symmetry and the annealing behaviour, we suggest a carbon vacancy-carbon antisite complex in the neutral charge state, VCVCCSi0, with the vacancies and the antisite in the basal plane, as a new defect model for the centre.

  • 12. Ellison, A.
    et al.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, W.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Storasta, Liutauras
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Henelius, N.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    HTCVD Growth of Semi-Insulating 4H-SiC Crystals With Low Defect Density2001In: Mat. Res. Soc. Symp. Proc., Vol. 640, 2001, p. H1.2-Conference paper (Refereed)
  • 13. Ellison, A
    et al.
    Magnusson, Björn
    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.
    Storasta, Liutauras
    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.
    HTCVD grown semi-insulating SiC substrates2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 33-38Conference paper (Refereed)
    Abstract [en]

    The low residual doping of HTCVD grown semi-insulating SiC crystals enables the use of decreased concentrations of compensating deep levels, thereby providing new material solutions for microwave devices. Depending on the growth conditions, high resistivity crystals with either a dominating Si-vacancy absorption or with an EPR signature of intrinsic defects such as the C-vacancy and the Si-antisite are obtained. The electrical properties of substrates with resistivities above 10(11) Omega-cm are shown to be stable upon annealing during SiC epitaxy conditions. Micropipe closing at the initial growth stage enables the demonstration of low defect density off- and on-axis 2 2-inch semi-insulating 4H SiC substrates with micropipe densities down to 1.2 cm(-2).

  • 14. Ellison, A
    et al.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Sundqvist, B
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Vehanen, A
    SiC crystal growth by HTCVD2004In: Materials Science Forum, Vols. 457-460, 2004, Vol. 457-460, p. 9-Conference paper (Refereed)
    Abstract [en]

    Advances in the development of the HTCVD technique for growth of bulk 2-inch diameter 4H SiC crystals are reviewed with demonstration of micropipe density down to 0.3 cm(-2), low crystal bending and X-ray rocking curve widths of 12". High Al doping in p-type substrates enables resistivities down to 0.5 Omega cm without increased micropipe density, while too high N doping causes spontaneous stacking faults formation in annealed n-type substrates. High purity semi-insulating wafers, grown under conditions reducing the incorporation of Si-vacancies, exhibit lower density of vacancy clusters and better properties for microwave device applications.

  • 15. Ellison, A.
    et al.
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    High Resistivity Silicon Carbide Single Crystal2003Patent (Other (popular science, discussion, etc.))
  • 16.
    Eriksson, Jens
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Rorsman, N
    Zirath, H
    Henry, Anne
    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.
    Ellison, A
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    A comparison of MESFETs on different 4H-Silicon carbide semi-insulating substrates2003In: Materials Science Forum Vols. 433-434, 2003, Vol. 433-4, p. 737-739Conference paper (Refereed)
    Abstract [en]

    DC and RF measurements for MESFET devices fabricated on three different 4H-SiC Semi-Insulating (SI) substrates are compared in this paper and the epilayers were grown simultaneously for all three wafers. The different wafers were processed during the same batch run. The MESFETs processed on the high-purity wafers showed less light sensitivity than those processed on the Vanadium doped wafer.

  • 17.
    Gogova, Daniela
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kasic, A
    Larsson, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Pecz, B
    Yakimova, Rositsa
    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 .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Tuomisto, F
    Saarinen, K
    Miskys, C
    Stutzmann, M
    Bundesmann, C
    Schubert, M
    Optical and structural characteristics of virtually unstrained bulk-like GaN2004In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 43, no 4A, p. 1264-1268Article in journal (Refereed)
    Abstract [en]

    Bulk-like GaN with high structural and optical quality has been attained by hydride vapor-phase exitapy (HVPE). The as-grown 330 mum-thick GaN layer was separated from the sapphire substrate by a laser-induced lift-off process. The full width at half maximum values of the X-ray diffraction (XRD) omega-scans of the free-standing material are 96 and 129 arcsec for the (1 0 -1 4) and (0 0 0 2) reflection, respectively, which rank among the smallest values published so far for free-standing HVPE-GaN. The dislocation density determined by plan-view TEM images is 1-2 x 10(7) cm(-2). Positron annihilation spectroscopy studies show that the concentration of Ga vacancy related defects is about 1.5 x 10(16) cm(-3). The high-resolution XRD, photoluminescence, mu-Raman, and infrared spectroscopic ellipsometry measurements consistently prove that the free-standing material is of high crystalline quality and virtually strain-free. Therefore it is suitable to serve as a substrate for stress-free growth of high-quality III-nitrides based device heterostructures.

  • 18.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Norstel AB, Norrköping, Sweden.
    Beyer, Franziska
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Budapest University of Technology and Economics and Hungarian Academy of Science, Budapest, Hungary .
    Son, Nguyen Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Electronic Configuration of Tungsten in 4H-, 6H-, and 15R-SiC2012In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 211-216Conference paper (Refereed)
    Abstract [en]

    A commonly observed unidentified photoluminescence center in SiC is UD-1. In this report, the UD-1 center is identified to be tungsten related. The identification is based on (i) a W-doping study, the confirmation of W in the samples was made using deep level transient spectroscopy (DLTS), (ii) the optical activation energy of the absorption of UD-1 in weakly n-type samples corresponds to the activation energy of the deep tungsten center observed using DLTS. The tungsten-related optical centers are reported in 4H-, 6H-, and 15R-SiC. Further, a crystal field model for a tungsten atom occupying a Si-site is suggested. This crystal field model is in agreement with the experimental data available: polarization, temperature dependence and magnetic field splitting.

  • 19.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Beyer, Franziska
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Budapest University of Technology and Economics, Hungary.
    Son Tien, Nguyen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Optical identification and electronic configuration of tungsten in 4H-and 6H-SiC2012In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 407, no 10, p. 1462-1466Article in journal (Refereed)
    Abstract [en]

    Several optically observed deep level defects in SiC are still unidentified and little is published on their behavior. One of the commonly observed deep level defects in semi-insulating SiC is UD-1. less thanbrgreater than less thanbrgreater thanThis report suggests that UD-1 is Tungsten related, based on a doping study and previously reported deep level transient spectroscopy data, as well as photo-induced absorption measurements. The electronic levels involved in the optical transitions of UD-1 are also deduced. The transitions observed in the photoluminescence of UD-1 are from a Gamma(C3v)(4), to two different final states, which transform according to Gamma(C3v)(5)circle plus Gamma(C3v)(6) and Gamma(C3v)(4), respectively.

  • 20.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Carlsson, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Beyer, Franziska
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Influence of Cooling Rate after High Temperature Annealing on Deep Levels in High-Purity Semi-Insulating 4H-SiC2007In: Materials Science Forum, vol. 556-557, Trans Tech Publications , 2007, p. 371-Conference paper (Refereed)
    Abstract [en]

    The influence of different cooling rates on deep levels in 4H-SiC after high temperature annealing has been investigated. The samples were heated from room temperature to 2300°C, followed by a 20 minutes anneal at this temperature. Different subsequent cooling sequences down to 1100°C were used. The samples have been investigated using photoluminescence (PL) and IV characteristics. The PL intensities of the silicon vacancy (VSi) and UD-2, were found to increase with a faster cooling rate.

  • 21.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ellison, A.
    Gali, Adam
    Wigner Research Center for Physics, Hungarian Academy of Sciences / Department of Atomic Physics, Budapest University of Technology and Economics, Hungary.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    A defect center for quantum computing: Mo in SiCManuscript (preprint) (Other academic)
    Abstract [en]

    The electronic structure and vibrational properties of molybdenum (Mo) in SiC are analyzed and investigated in detail. Mo is considered as occupying the silicon-carbon divacancy in the so-called asymmetric split vacancy (ASV) configuration. Group-theoretical considerations within this model are used to explain the experimental results (optical properties and behavior in magnetic field). The vibrational properties of the defect are studied using simple the “defect molecule” model with parameters determined phenomenologically from the experimental data. The position of Mo in the ASV configuration deduced from this model is shown to be in good agreement with the earlier reported data from ab initio supercell calculations. The usefulness of molybdenum in SiC in quantum computing is investigated, and it shown that Mo is a highly promising candidate for quantum computing.

  • 22.
    Gällström, Andreas
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Optical identification of Mo related deep level defect in 4H and 6H SiC2009In: Materials Science Forum Vols. 615-617, Trans Tech Publications , 2009, p. 405-408Conference paper (Refereed)
    Abstract [en]

    The photoluminescence (PL) from the I 1 centre is observed in p-, n-type as well as in compensated samples, using above band gap excitation. The PL from I 1 in the two polytypes 4H and 6H is very similar, the difference being the position of the main peak, in 4H 1.1521 eV and 1.1057 eV in 6H. We here suggest I-1 to be Mo related based on intentional doping, SIMS results and comparison with earlier reports of Mo in SiC using magnetic resonance techniques. From PL measurements, we analyze the electron structure of the defect, and suggest it be the neutral Mo (4d2) residing on a Si site, the luminescence coming from the transition between the 3A2 multiplet of the first excited electronic configuration and the ground state 3A2.

  • 23.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kordina, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Son, Nguyen Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Wigner Research Center for Physics, Hungarian Academy of Sciences, Hungary.
    Gali, Adam
    Wigner Research Center for Physics, Hungarian Academy of Sciences, Budapest Hungary; Department of Atomic Physics, Budapest University of Technology and Economics, Budapest, Hungary.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Materials Modeling and Development Laboratory, NUST “MISIS,” Moscow, Russia; LACOMAS Laboratory, Tomsk State University, Tomsk, Russia.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Optical properties and Zeeman spectroscopy of niobium in silicon carbide2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 7, p. 1-14, article id 075207Article in journal (Refereed)
    Abstract [en]

    The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H, and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si-C divacancy with both Si and C at hexagonal sites. Using this concept we propose a model considering a Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using first-principles calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is tentatively explained on the grounds of the proposed model and the concept that the Nb center can exist in both C1h and C3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at the hexagonal site in the studied SiC polytypes behaves like a deep acceptor.

  • 24.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Thuaire, A.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    The Electronic Structure of the UD-4 defect in 4H, 6H and 15R SiC2009In: Materials Science Forum, Vols. 600-603, Trans Tech Publications , 2009, p. 397-400Conference paper (Refereed)
    Abstract [en]

    The photoluminescence (PL) of the UD-4 defect is observed in semi-insulating bulk 4H, 6H and 15R SiC. In 4H and 6H SiC the UD-4 defect consists of two families of no-phonon (NP) lines, Ua and Ub, and in 15R SiC it consists of three families, Ua, Ub and U15R. The Ua family in 4H, 6H and 15R all show similar temperature behavior with higher energy NP lines becomming observable at higher temperatures. In the case of the Ub and U15R families, a luminescence line with lower energy than the prominent luminescence line appears at higher temperatures. The polarization and Zeeman measurements suggest that the defect has C3v symmetry.

  • 25.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Tien Son, Nguyen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Optical identification of intrinsic nearest-neighbor defects in SiC2015Manuscript (preprint) (Other academic)
    Abstract [en]

    The optical signature of two types of intrinsic nearest-neighbor defects in SiC is observed in 4H- and 6H-SiC. The first optical signature belong to a defect previously known as UD-2 and identified as the divacancy pair, and the second – to a defect referred to here as UD-0, an unidentified defect. In both these defects, the number of optical centers is equal to the number of possible configurations for nearest-neighbor pairs in the unit cells of these polytypes. The polarization of all optical transitions is investigated. The formation of the two defects by means of electron irradiation and subsequent annealing in samples with different Fermi levels is studied, too. The observed transitions are investigated using group-theoretical analysis and UD-0 is tentatively assigned to the carbon-vacancy carbonantisite pair, based on energy positions of the lines and spin configuration.

  • 26. Hahn, S.
    et al.
    Beyer, Franziska
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gällström, Andreas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Carlsson, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Henry, Anne
    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.
    Niklas, J.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Contact-Less Electrical Defect Characterization of Semi-Insulating 6H-SiC Bulk Material2009In: Materials Science Forum Vols. 600-603, Trans Tech Publications , 2009, p. 405-408Conference paper (Refereed)
    Abstract [en]

    The novel technique microwave detected photo induced current transient spectroscopy (MD-PICTS) was applied to semi-insulating 6H-SiC in order to investigate the properties of inherent defect levels. Defect spectra can be obtained in the similar way to conventional PICTS and DLTS. However, there is no need for contacting the samples, which allows for non-destructive and spatially resolved electrical characterization. This work is focused on the investigation of semi-insulating 6H-SiC grown under different C/Si-ratios. In the corresponding MD-PICTS spectra several shallow defect levels appear in the low temperature range. However the peak assignment needs further investigation. Additionally different trap reemission dynamics are obtained for higher temperatures, which are supposed to be due to different compensation effects.

  • 27.
    Henry, Anne
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ellison, A
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmet AB, SE-58330 Linkoping, Sweden.
    Forsberg, Urban
    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.
    Pozina, Galia
    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.
    Characterization of bulk and epitaxial SiC material using photoluminescence spectroscopy2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 593-596Conference paper (Refereed)
    Abstract [en]

    We are using low temperature photoluminescence (LTPL) to evaluate the quality of SiC wafers and are able to characterize up to 2 inch diameter wafers (with or without epilayers) at low temperature (2K). Polytype maps for bulk material can be drawn, as well as nitrogen concentration maps for both bulk and epilayer wafers in the very large doping range available today (from low 10(14) cm(-3) to 10(19) cm(-3)).

  • 28.
    Henry, Anne
    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.
    Linnarsson, MK
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden ABB Corp Res, SE-72178 Vasteras, Sweden Royal Inst Technol, Solid State Elect, SE-16440 Kista, Sweden Okmet AB, SE-58330 Linkoping, Sweden.
    Ellison, A
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden ABB Corp Res, SE-72178 Vasteras, Sweden Royal Inst Technol, Solid State Elect, SE-16440 Kista, Sweden Okmet AB, SE-58330 Linkoping, Sweden.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    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.
    Presence of hydrogen in SiC2001In: Materials Science Forum, Vols. 353-356, 2001, Vol. 353-3, p. 373-376Conference paper (Refereed)
    Abstract [en]

    An unexpected presence of hydrogen in 4H-SiC was revealed by the observation of hydrogen related lines in the low-temperature photoluminescence (LTPL) spectrum after secondary ion mass spectrometry (SIMS) measurements. The lines were not observed before SIMS. The high-energy ions during SIMS are proposed to break the boron-hydrogen bonds. This phenomenon is observable only for a certain impurity concentration in the material due to the competition of various recombination channels during the LTPL experiment.

  • 29.
    Ivanov, Ivan Gueorguiev
    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 .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Analysis of the sharp donor-acceptor pair luminescence in 4H-SiC doped with nitrogen and aluminum2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 16Article in journal (Refereed)
    Abstract [en]

    We analyze the sharp lines in the donor-acceptor (nitrogen-aluminum) emission spectrum in 4H-SiC by means of a fit with theoretically calculated spectra. The theory accounts for the anisotropy and the presence of inequivalent sites in this polytype of SiC, and it is shown that the predominant emission in the linear part of the spectrum is due to pairs involving nitrogen donor and aluminum acceptor at hexagonal sites. The fit allows determination of the ionization energy of the aluminum at hexagonal site, 199+/-2 meV, which is in excellent agreement with the results obtained using free-to-bound spectra.

  • 30.
    Ivanov, Ivan Gueorguiev
    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 .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Optical selection rules for shallow donors in 4H-SiC and ionization energy of the nitrogen donor at the hexagonal site2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 16Article in journal (Refereed)
    Abstract [en]

    The selection rules for transitions between the electronic levels of shallow donors in 4H-SiC in the dipole approximation are derived. The ionization energy of the shallow nitrogen donor (at hexagonal site) is determined to be 61.4+/-0.5 meV by analyzing the photothermal ionization and infrared absorption spectra of nitrogen doped samples in the frame of model that approximates the effective-mass Hamiltonian in 4H-SiC with Hamiltonian of cylindric symmetry (Faulkner's model).

  • 31.
    Janzén, Erik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Carlsson, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gällström, Andreas
    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.
    Son, Nguyen Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    The Silicon vacancy in SiC2009In: / [ed] Amador Pérez-Tomás, Philippe Godignon, Miquel Vellvehí and Pierre Brosselard, Trans Tech Publications Inc., 2009, Vol. 615-617, p. 347-352Conference paper (Refereed)
    Abstract [en]

     A model is presented for the silicon vacancy in SiC. The previously reported photoluminescence spectra in 4H and 6H SiC attributed to the silicon vacancy are in this model due to internal transitions in the negative charge state of the silicon vacancy. The magnetic resonance signals observed are due to the initial and final states of these transitions.

  • 32.
    Janzén, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Budapest University Technology and Econ, Department Atom Phys, H-1111 Budapest, Hungary .
    Carlsson, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gällström, Andreas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    The silicon vacancy in SiC2009In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 404, no 22, p. 4354-4358Article in journal (Refereed)
    Abstract [en]

    The isolated silicon vacancy is one of the basic intrinsic defects in SiC. We present new experimental data as well as new calculations on the silicon vacancy defect levels and a new model that explains the optical transitions and the magnetic resonance signals observed as occurring in the singly negative charge state of the silicon vacancy in 4H and 6H SiC.

  • 33.
    Janzén, Erik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Henry, Anne
    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.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Nguyen, Son Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Defects in SiC2008In: Defects in Microelectronic Materials and Devices / [ed] Daniel M. Fleetwood, Sokrates T. Pantelides, Ronald D. Schrimpf., Taylor and Francis LLC , 2008, p. 770-Chapter in book (Other academic)
    Abstract [en]

    Uncover the Defects that Compromise Performance and Reliability As microelectronics features and devices become smaller and more complex, it is critical that engineers and technologists completely understand how components can be damaged during the increasingly complicated fabrication processes required to produce them.

    A comprehensive survey of defects that occur in silicon-based metal-oxide semiconductor field-effect transistor (MOSFET) technologies, this book also discusses flaws in linear bipolar technologies, silicon carbide-based devices, and gallium arsenide materials and devices. These defects can profoundly affect the yield, performance, long-term reliability, and radiation response of microelectronic devices and integrated circuits (ICs). Organizing the material to build understanding of the problems and provide a quick reference for scientists, engineers and technologists, this text reviews yield- and performance-limiting defects and impurities in the device silicon layer, in the gate insulator, and/or at the critical Si/SiO2 interface. It then examines defects that impact production yield and long-term reliability, including:

    • Vacancies, interstitials, and impurities (especially hydrogen)

    • Negative bias temperature instabilities

    • Defects in ultrathin oxides (SiO2 and silicon oxynitride)

    Take A Proactive Approach The authors condense decades of experience and perspectives of noted experimentalists and theorists to characterize defect properties and their impact on microelectronic devices. They identify the defects, offering solutions to avoid them and methods to detect them. These include the use of 3-D imaging, as well as electrical, analytical, computational, spectroscopic, and state-of-the-art microscopic methods. This book is a valuable look at challenges to come from emerging materials, such as high-K gate dielectrics and high-mobility substrates being developed to replace Si02 as the preferred gate dielectric material, and high-mobility substrates

  • 34.
    Janzén, Erik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Henry, Anne
    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.
    Ellison, A.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Material characterization need for SiC-based devices2001In: Sci. Eng. B, Vol. 4, 2001, Vol. 4, no 1-3, p. 181-186Conference paper (Refereed)
    Abstract [en]

    The simultaneous development of suitable characterization techniques that provide fast feedback to the growth as well as basic material understanding have enabled the fast development of epitaxial and bulk growth of SiC. The characterization techniques can roughly be divided into two different categories, routine characterization that are made on most grown material and specialized characterization that are performed in order to study and understand specific material properties. The routine measurements described in this paper are all based on optical and non-destructive techniques. The main effort in this field is currently to study and understand the role of structural defects, often replicated from the substrate into the epilayer.

  • 35.
    Janzén, Erik
    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.
    Nguyen, Son Tien
    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.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Isoya, J.
    Defects in SiC2004Conference paper (Other academic)
  • 36.
    Janzén, Erik
    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.
    Nguyen, Son Tien
    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.
    Zolnai, Z
    Henry, Anne
    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.
    Storasta, Liutauras
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Carlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Defects in SiC2003In: Physica B: Condensed Matter, Vols. 340-342, 2003, Vol. 340, p. 15-24Conference paper (Refereed)
    Abstract [en]

    Recent results from studies of shallow donors, pseudodonors, and deep level defects in SiC are presented. The selection rules for transitions between the electronic levels of shallow donors in 4H-SiC in the dipole approximation are derived and the ionization energy for the N donor at hexagonal site is determined. Optical and electrical studies of the D-I center reveal the pseudodonor nature of this defect. Defects in high-purity semi-insulating (SI) SiC substrates including the carbon vacancy (V-C), silicon vacancy (V-Si), and (V-C-C-Si) pair are studied. The annealing behavior of these defects and their role in carrier compensation in SI 4H-SiC are discussed. (C) 2003 Elsevier B.V. All rights reserved.

  • 37.
    Janzén, Erik
    et al.
    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.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ellison, A
    Intrinsic defects in high-purity SiC2006In: Microelectronic Engineering, Vol. 83, 2006, Vol. 83, no 1, p. 130-134Conference paper (Refereed)
    Abstract [en]

    Intrinsic defects are of importance for different applications of SiC such as: the semi-insulating (SI) properties of SI substrates, the carrier lifetime of high-voltage, bipolar power devices and the colour of gemstones (Moissanites). In order to tailor the properties of the material, we need to understand the properties of the intrinsic defects, their energy positions in the bandgap, their ability to capture carriers from the bands, their formation and annealing as well as their interplay with other defects. High-purity SiC materials (doping less than 10(16) cm(-3)) grown by high temperature chemical vapour deposition (HTCVD), physical vapour transport (PVT) and chemical vapour deposition (CVD) have been investigated by electron paramagnetic resonance (EPR), photoluminescence (PL), absorption and electrical techniques. Vacancies (V-C(+), V-Si(0)), divacancies and anti site-related defects are found to be common. The present knowledge of intrinsic defects in SiC based on both experiments and on calculations will be presented as well as their influence on mainly the semi-insulating properties. (c) 2005 Elsevier B.V. All rights reserved.

  • 38.
    Kakanakova-Georgieva, Anelia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Forsberg, Urban
    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.
    Yakimova, Rositsa
    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.
    Growth of AlN films by hot-wall CVD and sublimation techniques: Effect of growth cell pressure2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 1469-1472Conference paper (Refereed)
    Abstract [en]

    Aluminum nitride (AlN) films were grown on off-axis, Si-terminated 4H-SiC substrates by hot-wall CVD and sublimation techniques. The films were investigated by Infrared reflectance, Optical microscopy, Energy Dispersive X-ray analysis and Cathodoluminescence in a Scanning Electron Microscope with respect to their thickness, morphological, compositional and luminescence properties, in order to examine the influence of the growth cell pressure in either of the two deposition methods. Good quality thick AlN films were obtained by hot-wall CVD at temperature of 1200degreesC and reduced pressure of 100 mbar as reflected in the near stoichiometric N/Al ratio in these layers and in the appearance of the characteristic AlN near band edge emission. The AlN sublimation grown films at temperature of 2100degreesC suffered from island growth irrespective of the background pressure. The supersaturation conditions that affect strongly the growth mode became more favorable when the temperature was reduced to 1900degreesC.

  • 39. Kassamakova-Kolaklieva, L.
    et al.
    Storasta, Liutauras
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ivanov, Ivan Gueorguiev
    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.
    Contreras, S.
    Consejo, C.
    Pernot, J.
    Zielinski, M.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Temperature-Dependent Hall Effect Measurements in Low - Compensated p-Type 4H-SiC2004In: Mater. Sci. Forum, Vol. 457-460, Trans Tech Publications Inc. , 2004, p. 677-Conference paper (Refereed)
    Abstract [en]

      

  • 40.
    Magnusson, Björn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Aavikko, R.
    Saarinen, K.
    Nguyen, Son Tien
    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.
    Optical Studies of Deep Centers in Semi-Insulating SiC2006In: Materials Science Forum, Vols. 527-529, 2006, p. 455-Conference paper (Refereed)
  • 41.
    Magnusson, Björn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, JP
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Time-resolved photoluminescence of deep centers in semi-insulating 4H-SiC2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 301-304Conference paper (Refereed)
    Abstract [en]

    Deep levels (V, Cr, UD-1 and UD-3) have been studied with time resolved photoluminescence. The decay time is determined as 193 ns, 58 mus, 247 ns and 51.5 mus for the V, Cr, UD-1 and UD-3 centers, respectively, at low temperature (2 K). The relatively long decay times indicate that the radiative recombination is dominant at low temperatures. By fitting the temperature dependence of the decay time, the activation energies of the V and UD-1 centers are determined as 160 meV and 50 meV respectively.

  • 42.
    Magnusson, Björn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ellison, A
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmet AB, SE-58330 Linkoping, Sweden.
    Carlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    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.
    As-grown and process-induced intrinsic deep-level luminescence in 4H SiC2001In: Materials Science Forum, Vols. 353-356, Trans Tech Publications Inc., 2001, Vol. 353-356, p. 365-368Conference paper (Refereed)
    Abstract [en]

    A deep level in 4H SiC is studied by photoluminescence (PL) for different annealing temperatures. The luminescence consists of four no-phonon lines between 1.09 and 1.15 eV and their phonon assisted spectra. No splitting or shifting of the lines could be observed in a magnetic field up to 5T. The defect can be introduced in the material by either ion implantation or irradiation, but may also be present in as-grown samples. The PL intensity increases with annealing up to 1000 degreesC, thereafter decreases and vanishes at 1300 degreesC. We tentatively ascribe this deep level defect to a silicon vacancy related complex.

  • 43.
    Magnusson, Björn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ellison, A
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmetic AB, SE-58330 Linkoping, Sweden.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Properties of the UD-1 deep-level center in 4H-SiC2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 505-508Conference paper (Refereed)
    Abstract [en]

    Results from absorption measurements in semi-insulating 4H-SiC HTCVD-grown substrates show that the infrared absorption spectra is dominated by the UD-1 defect. The UD-1 spectrum has two sharp lines around I eV. The activation energy of the T-dependence of the resistivity in the semi-insulating material, which has a strong absorption by the UD-1 defect, is determined to be 1.4 eV. Photo-induced absorption measurements show that the absorption of the UD-1 defect increases when the sample is illuminated with 1.4 eV. When the energy of the exciting light reaches 1.85 eV the absorption intensity starts to decrease. In this way we have been able to correlate the electrical behavior (with a thermal activation energy of 1.4 eV) of the HTCVD 4H-SiC material with the UD-1 defect which we observe in luminescence and absorption measurements.

  • 44.
    Magnusson, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ellison, A.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Deep-level luminescence at 1.0 eV in 6H SiC2001In: Mat. Res. Soc. Symp. Proc., Vol. 640, 2001Conference paper (Refereed)
    Abstract [en]

    Results from photoluminescence (PL) and Zeeman effect measurements of a PL center, labeled UD-1, in 6H SiC are presented. The spectrum consists of three no phonon-lines (NPLs) at 0.9952, 1.0015 and 1.0020 eV. The luminescence starts decreasing in intensity above 40 K and is completely quenched at 80 K. The observed Zeeman splitting reveals a spin one half of the ground state of the two highest energy lines. No splitting of the 0.9952 eV line is detected. The g-value for the 1.0015 eV and 1.0020 e lines are g = 1:4 and g = 1:7, respectively. For both lines, g = 0. The C3v symmetry indicates that the UD-1 center is either a substitutional defect or a complex with its constituents lying along the c-axis of the lattice.

  • 45.
    Magnusson, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ellison, A.
    Storasta, Liutauras
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Infrared absorption and annealing behavior of semi-insulating 4H SiC HTCVD substrates2001In: Proc. of the MRS Spring Meeting (2001), Vol. 680E, 2001, p. E5.11-Conference paper (Refereed)
  • 46.
    Magnusson, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Optical Characterization of Deep Level Defects in SiC2005In: Materials Science Forum, Vols. 483-485 / [ed] Roberta Nipoti, Antonella Poggi and Andrea Scorzoni, 2005, Vol. 483-485, p. 341-346Conference paper (Refereed)
    Abstract [en]

    Deep levels in 4H- and 6H-SiC are characterized by FTIR spectroscopy. Vanadium, chromium and the silicon vacancy related center are listed together with the unidentified defects with emission and absorption in the near IR region. We suggest the UD-1, UD-3 and I-1 to be impurity related while the UD-2 and UD-4 to be intrinsic defects based on annealing behavior and the possibility to create the defect with irradiation. We have also tentatively assigned a new defect center around 1.0 eV to the carbon vacancy-antisite pair instead of the earlier assignment to the UD- 2 defect in 4H-SiC. We have shown that to get more information about the SiC samples a combination of absorption and luminescence techniques are very useful. Further, the use of below bandgap selective excitation is necessary to obtain more information about the defects present in the sample. FTIR absorption and luminescence measurements are useful tools to characterize deep levels important for both semi-insulating material as well as low doped conducting material where the free carrier lifetime is limited by deep levels.

  • 47.
    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.

  • 48.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Carlsson, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Gällström, Andreas
    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 .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Deep levels and carrier compensation in V-doped semi-insulating 4H-SiC2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 20Article in journal (Refereed)
    Abstract [en]

    Electron paramagnetic resonance was used to study semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range of 5.5× 1015 -1.1× 1017 cm-3. Our results show that the electrical activation of V is low and hence only in heavily V-doped 4H-SiC, vanadium is responsible for the SI behavior, whereas in moderately V-doped substrates, the SI properties are thermally unstable and determined by intrinsic defects. We show that the commonly observed thermal activation energy Ea ∼1.1 eV in V-doped 4H-SiC may be related to deep levels of the carbon vacancy. © 2007 American Institute of Physics.

  • 49.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Carlsson, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gällström, Andreas
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Deep Levels Responsible for Semi-insulating Behaviour in Vanadium-doped 4H-SiC Substrates2009In: Materials Science Forum, Vols. 600-603, Trans Tech Publications , 2009, p. 401-404Conference paper (Refereed)
    Abstract [en]

    Semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range 5.5×1015 –1.1×1017 cm–3 were studied by electron paramagnetic resonance. We show that only in heavily V-doped 4H-SiC vanadium is responsible for the SI behavior, whereas in moderate V-doped substrates with the V concentration comparable or slightly higher than that of the shallow N donor or B acceptor, the SI properties are thermally unstable and determined by intrinsic defects. The results show that the commonly observed thermal activation energy Ea~1.1 eV in V-doped 4H-SiC, which was previously assigned to the single acceptor V4+/3+ level, may be related to deep levels of the carbon vacancy. Carrier compensation processes involving deep levels of V and intrinsic defects are discussed and possible thermal activation energies are suggested.

  • 50.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Carlsson, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gällström, Andreas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    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.
    Prominent defects in semi-insulating SiC substrates2007In: Physica B, Vol. 401-402, Elsevier , 2007, p. 67-Conference paper (Refereed)
    Abstract [en]

      

12 1 - 50 of 74
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