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  • 1.
    Aradi, B
    et al.
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Deak, P
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    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.
    Impurity-controlled dopant activation - The role of hydrogen in p-type doping of SiC2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 561-564Conference paper (Refereed)
    Abstract [en]

    Hydrogen is a natural contaminant of SiC growth processes, and may influence the doping efficiency. Hydrogen incorporation proportional to that of boron was observed during CVD growth while the amount of hydrogen was two orders of magnitude less than the aluminum concentration. Passivation by complex formation with hydrogen has been proven both for Al and B. The experimentally observed reactivation energy of these complexes differ by 0.9 eV. Our ab initio supercell calculations in 4H-SiC indicate, that in the absence of hydrogen, boron is incorporated as isolated substitutional and prefers the carbon site, while under typical CVD conditions boron is incorporated together with hydrogen (in equal amounts), favoring the silicon site. Therefore, the presence of H is advantageous for the activation of B as a shallow acceptor. In contrast to boron, aluminum is incorporated independently of the presence of hydrogen as isolated substitutional at the silicon site. The calculated difference between the dissociation of the stable dopant plus hydrogen complexes agrees very well with experiments. Vibration frequencies for the dopant complexes have been also calculated.

  • 2.
    Aradi, B.
    et al.
    Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    Gali, Adam
    Department of Atomic Physics, Budapest Univ. of Technol./Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    Deak, P.
    Deák, P., Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    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.
    Passivation of p-type dopants in 4H-SiC by hydrogen2001In: Physica B, Vols. 308-310, 2001, Vol. 308-310, p. 722-725Conference paper (Refereed)
    Abstract [en]

    Experimental investigations showed passivation of the p-type dopants B and Al in 4H-SiC by the formation of B+H and Al+H complexes. The dissociation energies of these complexes differed by 0.9 eV. Ab initio supercell calculations have been performed to investigate the interaction of H with B and Al in hexagonal 4H-SiC. The total energy, geometry and electronic structure of the possible complexes have been determined. Site dependencies have also been investigated. The most stable configurations were found with H at a bond center site next to B at the Si site, and with H at the antibonding site of a carbon atom which is first neighbor to Al at a Si site. Both the BSi+HBC and the AlSi+HAB(C) complexes turned out to be electrically inactive. The different structure of the passivated complexes explains the observed difference in their dissociation energy: the calculated difference of the binding energies of these complexes is 0.9 eV, which agrees well with the experimental finding. © 2001 Elsevier Science B.V. All rights reserved.

  • 3.
    Aradi, B
    et al.
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Univ Gesamthsch Paderborn, Dept Phys, DE-33095 Paderborn, Germany Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Deak, P
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Univ Gesamthsch Paderborn, Dept Phys, DE-33095 Paderborn, Germany Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Rauls, E
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Univ Gesamthsch Paderborn, Dept Phys, DE-33095 Paderborn, Germany Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Frauenheim, T
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Univ Gesamthsch Paderborn, Dept Phys, DE-33095 Paderborn, Germany Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Boron centers in 4H-SiC2001In: Materials science Forum, Vols. 353-356, 2001, Vol. 353-356, p. 455-458Conference paper (Refereed)
    Abstract [en]

    The origin of the "deep boron related acceptor level" in SIC is subject to a lot of controversy. Based on ENDOR investigations, a B-Si+V-C model was suggested, while PL studies indicated the acceptor on the carbon sublattice. Our former ab initio LDA molecular cluster calculation showed that in the B-Si+V-C complex the carbon vacancy acts as the acceptor. Now, ah initio LDA supercell calculations have been carried out for boron-related complexes to calculate the occupation levels in 4H-SiC. It has been found that the 0/- level for the B-Si+V-C complex lies in the upper half of the gap, therefore it can be disregarded as the origin of the "deep boron-related acceptor level". Investigating other feasible boron-related complexes, B-Si+Si-C appears to be the best candidate.

  • 4.
    Deak, P
    et al.
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA.
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Aradi, B
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA.
    Nguyen, Tien Son
    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.
    Choyke, WJ
    Tech Univ Budapest, Dept Atom Phys, HU-1111 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA.
    Vacancies and their complexes with H in SiC2000In: Materials Science Forum, Vols. 338-343, Stafa-Zurich, Switzerland: Trans Tech Publications Inc., 2000, Vol. 338-342, p. 817-820Conference paper (Refereed)
    Abstract [en]

    Ab initio calculations (LDA and MCSF) have been carried out for vacancies (V-Si and V-C) and interstitial H, as well as for V+H complexes in 3C SiC. Relative stability of different charge-states/configurations and occupation levels were determined in supercells with plane wave basis sets while vibration frequencies and spin distributions were calculated in clusters with localized basis functions. Both types of vacancies show amphoteric electrical activity. In equilibrium, atomic He is at the AB(C), and H is at the T-Si site, while H-0 does not appear to be stable with respect to them, so H can also act both as a deep donor and an electron trap. Hydrogen can passivate the V-Si acceptor but not the V-C donor. Conditions for the formation of the possible V+H centers and their properties are given and used to discuss experimental information (or the lack of them) about H in SiC.

  • 5. Deak, P
    et al.
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Hajnal, Z
    Frauenheim, T
    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.
    Choyke, WJ
    Ordejon, P
    A cause for SiC/SiO2 interface states: The site selection of oxygen in SiC2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 535-538Conference paper (Refereed)
    Abstract [en]

    We show that in the SiC/SiO2 system the interface states in the lower half of the gap are the consequence of the behavior of oxygen in SiC. Investigating the elemental steps of oxidation on a simple model by means of ab initio density functional calculations we find that, in course of the oxidation, carbon-vacancy (V-C) - oxygen complexes constantly arise. The V-C+O complexes have donor states around E-V+0.8 eV. Their presence gives rise to a thin transition layer which is not SiO2 but an oxygen contaminated Si-rich interface layer producing the aforementioned gap states.

  • 6.
    Gali, Adam
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Aradi, B
    Tech Univ Budapest, Dept Atom Phys, H-1111 Budapest, Hungary Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Deak, P
    Tech Univ Budapest, Dept Atom Phys, H-1111 Budapest, Hungary Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Choyke, WJ
    Tech Univ Budapest, Dept Atom Phys, H-1111 Budapest, Hungary Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Overcoordinated hydrogens in the carbon vacancy: Donor centers of SiC2000In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 84, no 21, p. 4926-4929Article in journal (Refereed)
    Abstract [en]

    Epitaxial silicon carbide is likely to contain hydrogen and vacancies (V), therefore, V + nH complexes are likely to influence its electronic properties. Using ob initio calculations we show that neutral and positive H atoms are trapped by carbon vacancies (V-C) in three-center bonds with two Si neighbors. The double positive charge state of V-C + H is not stable in equilibrium and in the triply positive state H binds only to one of the Si neighbors. At most two H atoms can be accommodated by a single V-C. The V-C + nH complexes have donor character and exhibit rather atypical vibration modes for Si-H bonds. Occupation levels and spin distributions were calculated and compared fur V-C + H and V-C.

  • 7.
    Gali, Adam
    et al.
    Department of Atomic Physics, Budapest Univ. of Technol./Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    Deak, P.
    Deák, P., Department of Atomic Physics, Budapest Univ. of Technol./Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    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.
    Hydrogen passivation of nitrogen in SiC2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 83, no 7, p. 1385-1387Article in journal (Refereed)
    Abstract [en]

    A study is performed on hydrogen passivation of nitrogen in SiC. The first-principles calculations show that hydrogen may form stable complexes with substitutional nitrogen, passivating the shallow nitrogen donor. It is found that the complex is stable with respect to negatively charged hydrogen interstitials and isolated positive donors.

  • 8.
    Gali, Adam
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Deak, P
    Budapest Univ Technol & Econ, Dept Atom Phys, HU-1111 Budapest, Hungary Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    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.
    Theoretical investigation of an intrinsic defect in SiC2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 477-480Conference paper (Refereed)
    Abstract [en]

    Ab initio calculation of the local vibrational modes of a carbon pair in the silicon vacancy (V-Si+2C) shows that it cannot be the origin of the D-II photoluminescence (PL) center, however, it seems likely, that this defect gives rise to the Ramanpeaks observed at 1080 and 1435 cm(-1) in proton irradiated samples. Occupation levels of the V-Si+2C defect are also predicted to facilitate experimental confirmation.

  • 9.
    Gali, Adam
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Deak, P
    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.
    von Bardeleben, HJ
    Monge, JL
    Calculation of hyperfine constants of defects in 4H-SiC2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 511-514Conference paper (Refereed)
    Abstract [en]

    Knowledge about the creation and diffusion of intrinsic point defects is crucial for devising annealing strategies after irradiation steps as, e.g., implantation. Experimental information can be obtained by observing the appearance and/or disappearance of characteristic electrical, optical or magnetic spectra, however, these have to be first assigned to a given defect. In case of silicon carbide even this very first task has not been accomplished yet in case of the carbon vacancy, with which two different electron spin resonance (ESR) centers (anneling out at very different temperatures) have been identified. Ab initio all-electron supercell calculations have been carried out to determine the hyperfine constants of several defects in 4H-SiC in order to justify the models of the measured ESR signals. The quality of the results were tested on the well-documented case of interstitial hydrogen in silicon.

  • 10.
    Gali, Adam
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Deak, P
    Ordejon, P
    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.
    Choyke, WJ
    Aggregation of carbon interstitials in silicon carbide: A theoretical study2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 12Article in journal (Refereed)
    Abstract [en]

    Ab initio supercell calculations have been carried out to investigate clusters of carbon interstitials in 3C- and 4H-SiC. Based on the calculated formation energies, the complex formation of carbon interstitials or their aggregation to carbon antisites is energetically favored in SiC. The electronic and vibronic properties of the carbon interstitials and their aggregates depends strongly on the polytype. Using the calculated hyperfine constants and local vibrational modes of carbon clusters the possible relation to known carbon-related centers will be discussed.

  • 11.
    Gali, Adam
    et al.
    Department of Atomic Physics, Budapest Univ. of Technol./Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    Deak, P.
    Deák, P., Department of Atomic Physics, Budapest Univ. of Technol./Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    Rauls, E.
    Theoretische Physik, Universität Paderborn, D-33098 Paderborn, Germany.
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Choyke, W.J.
    Department of Physics, University of Pittsburgh, Pittsburgh, PA 15260, United States.
    Anti-site pair in SiC: A model of the DI center2003In: Physica B, 2003, Vol. 340-342, p. 175-179Conference paper (Refereed)
    Abstract [en]

    The DI low-temperature photoluminescence center is a well-known defect stable up to 1700°C annealing in SiC, still its structure is not known after decades of study. Combining experimental and theoretical studies in this paper we will show that the properties of an anti-site pair can reproduce the measured one-electron level position and local vibration modes of the D I center and the model is consistent with other experimental findings as well. We give theoretical values of the hyperfine constants of the anti-site pair in its paramagnetic state as a means to confirm our model. © 2003 Elsevier B.V. All rights reserved.

  • 12.
    Gali, Adam
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Deak, P
    Rauls, E
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Choyke, WJ
    Correlation between the antisite pair and the D-I center in SiC2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 15Article in journal (Refereed)
    Abstract [en]

    The D-I low temperature photoluminescence center is a well-known defect stable up to 1700 degreesC annealing in SiC, still its structure is not yet known. Combining experimental and theoretical studies, in this paper we will show that the properties of an antisite pair can reproduce the measured one-electron level position and local vibration modes of the D-I center, and are consistent with other experimental findings as well. We give theoretical values of the hyperfine constants of the antisite pair in its paramagnetic state as a means to confirm a model.

  • 13. Gali, Adam
    et al.
    Deák, P.
    Rauls, E.
    Nguyen, Son Tien
    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.
    Carlsson, Fredrik
    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.
    Choyke, W.J.
    Antisites as possible origin of irradiation induced photoluminescence centers in SiC: A theoretical study on clusters of antisites and carbon interstitials in 4H-SiC2004In: Mater. Sci. Forum, Vol. 457-460, Trans Tech Publications Inc. , 2004, p. 443-Conference paper (Refereed)
  • 14.
    Gali, Adam
    et al.
    Department of Atomic Physics, Budapest Univ. of Technol./Economics, Budafoki út 8, H-1111 Budapest, Hungary.
    Gällström, Andreas
    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.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Theory of neutral divacancy in SiC: a defect for spintronics2010In: Materials Science Forum, Vols. 645-648, Trans Tech Publications , 2010, p. 395-397Conference paper (Refereed)
  • 15.
    Gali, Adam
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Umeda, T.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Morishita, N.
    Ohshima, T.
    Isoya, J.
    Identification of the Di-Carbon Antisite Defect in n-type 4H-SiC2009In: Materials Science Forum Vols. 615-617, Trans Tech Publications , 2009, p. 361-Conference paper (Refereed)
    Abstract [en]

      

  • 16.
    Gueorguiev Ivanov, Ivan
    et al.
    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.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kordina, Olle
    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.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology. 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 properties of the niobium centre in 4H, 6H, and 15R SiC2013In: SILICON CARBIDE AND RELATED MATERIALS 2012, Trans Tech Publications , 2013, Vol. 740-742, p. 405-408Conference paper (Refereed)
    Abstract [en]

    A set of lines in the photoluminescence spectra of 4H-, 6H-, and 15R-SiC in the near-infrared are attributed to Nb-related defects on the ground of doping experiments conducted with 4H-SiC. A model based on a an exciton bound at the Nb-centre in an asymmetric split vacancy configuration at a hexagonal site is proposed, which explains the structure of the luminescence spectrum and the observed Zeeman splitting of the lines.

  • 17.
    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.

  • 18. Isoya, J
    et al.
    Katagiri, M
    Umeda, T
    Koizumi, S
    Kanda, H
    Nguyen, Tien Son
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    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.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pulsed EPR studies of phosphorus shallow donors in diamond and SiC2006In: Physica B, Vols. 376-377, 2006, Vol. 376, p. 358-361Conference paper (Refereed)
    Abstract [en]

    Phosphorus shallow donors having the symmetry lower than T-d are studied by pulsed EPR. In diamond:P and 3C-SiC:P, the symmetry is lowered to D-2d and the density of the donor wave function on the phosphorus atom exhibits a predominant p-character. In 4H-SiC:P with the site symmetry of C-3v, the A(1) ground state of the phosphorus donors substituting at the quasi-cubic site of silicon shows an axial character of the distribution of the donor wave function in the vicinity of the phosphorus atom. (c) 2005 Elsevier B.V. All rights reserved.

  • 19.
    Ivady, V.
    et al.
    Hungarian Academic Science, Hungary .
    Somogyi, B.
    Budapest University of Technology and Economics, Hungary .
    Zolyomi, V.
    Hungarian Academic Science, Hungary .
    Gällström, Andreas
    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.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Transition Metal Defects in Cubic and Hexagonal Polytypes of SiC: Site Selection, Magnetic and Optical Properties from ab initio Calculations2012In: Materials Science Forum Vol 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 205-210Conference paper (Refereed)
    Abstract [en]

    Relatively little is known about the transition metal defects in silicon carbide (SiC). In this study we applied highly convergent and sophisticated density functional theory (DFT) based methods to investigate important transition metal impurities including titanium (Ti), vanadium (V), niobium (Nb), chromium (Cr), molybdenum (Mo) and tungsten (W) in cubic 3C and hexagonal 4H and 6H polytypes of SiC. We found two classes among the considered transition metal impurities: Ti, V and Cr clearly prefer the Si-substituting configuration while W, Nb, and Mo may form a complex with a carbon vacancy in hexagonal SiC even under thermal equilibrium with similar concentration. If the metal impurity is implanted into SiC or when many carbon impurities exist during the growth of SiC then complex formation between the Si-substituting metal impurity and the carbon vacancy should be considered. This complex pair configuration exclusively prefers the hexagonal-hexagonal sites in hexagonal polytypes and may be absent in the cubic polytype. We also studied transition metal doped nano 3C-SiC crystals in order to check the effect of the crystal field on the d-orbitals of the metal impurity.

  • 20.
    Ivády, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Theoretical investigation of the single photon emitter carbon antisite-vacancy pair in 4H-SiC2014In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Trans Tech Publications , 2014, Vol. 778-780, p. 495-498Conference paper (Refereed)
    Abstract [en]

    Well addressable and controllable point defects in device friendly semiconductors are desired for quantum computational and quantum informational processes. Recently, such defect, an ultra-bright single photon emitter, the carbon antisite - vacancy pair, was experimentally investigated in 4H-SiC. In our theoretical work, based on ab initio calculation and group theory analysis, we provide a deeper understanding of the features of the electronic structures and the luminescence process of this defect.

  • 21.
    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.

  • 22.
    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

  • 23.
    Nguyen, Son Tien
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Isoya, J.
    Morishita, N.
    Ohshima, T.
    Itoh, H.
    Gali, Adam
    Linköping University, The Institute of Technology. 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.
    Defects introduced by electron-irradiation at low temperatures in SiC2009In: Materials Science Forum Vols. 615-617, Trans Tech Publicarions , 2009, p. 377-380Conference paper (Refereed)
    Abstract [en]

    Defects introduced by electron irradiation at ~80-100 K in 3C-, 4H- and 6H-SiC were studied by electron paramagnetic resonance (EPR). A number of EPR spectra, labelled LE1-10, were detected. Combining EPR and supercell calculations, we will show that the LE1 center in 3C-SiC with C2v symmetry and an electron spin S=3/2 is related to the (VSi-Sii)3+ Frenkel pair between the silicon vacancy and a second neighbour Sii interstitial along the <100> direction. Results on other centers, possibly also related to interstitials, are discussed.

  • 24.
    Nguyen, Son Tien
    et al.
    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.
    Isoya, J.
    University of Tsukuba.
    Morishita, N.
    Japan Atomic Energy Agency.
    Hanaya, H.
    Japan Atomic Energy Agency.
    Takizawa, H.
    Japan Atomic Energy Agency.
    Ohshima, T.
    Japan Atomic Energy Agency.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Identification of a Frenkel-pair defect in electron-irradiated 3C SiC2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, p. 125201-Article in journal (Refereed)
    Abstract [en]

    Anelectron paramagnetic resonance (EPR) spectrum labeled LE1 was observed inn-type 3C SiC after electron irradiation at low temperatures (~80–100  K).A hyperfine interaction with four nearest C neighbors similar tothat of the well-known silicon vacancy in the negative chargestate was observed, but the LE1 center has a lowersymmetry, C2v. Supercell calculations of different configurations of silicon vacancy-interstitialFrenkel-pairs, VSi-Sii, were performed showing that pairs with a nearestneighbor Si interstitial are unstable—VSi and Sii will automatically recombine—whereaspairs with a second neighbor Sii are stable. Comparing thedata obtained from EPR and supercell calculations, the LE1 centeris assigned to the Frenkel-pair between VSi and a secondneighbor Sii interstitial along the [100] direction in the 3+charge state, V-Si. In addition, a path for the migrationof Si was found in 3C SiC. In samples irradiatedat low temperatures, the LE1 Frenkel-pair was found to bethe dominating defect whereas EPR signals of single vacancies werenot detected. The center disappears after warming up the samplesto room temperature.

  • 25.
    Nguyen, Tien Son
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Umeda, T
    Isoya, J
    Gali, Adam
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Bockstedte, M
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ellison, A
    Morishita, N
    Ohshima, T
    Itoh, H
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Identification of divacancies in 4H-SiC2006In: Physica B: Condensed Matter, Vols. 376-377, 2006, Vol. 376, p. 334-337Conference paper (Refereed)
    Abstract [en]

    The P6/P7 centers in 4H-SiC were studied by electron paramagnetic resonance (EPR) and ab initio supercell calculations. The hyperfine coupling constants of C and Si neighbors obtained by EPR are in good agreement with the calculated values for the neutral divacancy, VCVsi0. Our results suggest that the P6/P7 centers, which were previously assigned to the photo-excited triplet states of the carbon vacancy-carbon antisite pairs in the double positive charge state (VCCsi2+), are related to the triplet ground states of the C-3v/C-1h si configurations of VCVsi0 (c) 2006 Elsevier B.V. All rights reserved.

  • 26.
    Son, Nguyen Tien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivady, V.
    Hungarian Academy of Sciences, Budapest, Hungary.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Gällström, Andreas
    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.
    Kordina, Olle
    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.
    Identification of Niobium in 4H-SiC by EPR and ab Initio Studies2012In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 217-220Conference paper (Refereed)
    Abstract [en]

    In unintentionally Nb-doped 4H-SiC grown by high-temperature chemical vapor deposition (HTCVD), an electron paramagnetic resonance (EPR) center with C-lh symmetry and an electron spin S=1/2 was observed. The spectrum shows a hyperfine structure consisting of ten equal-intensity hyperfine (hf) lines which is identified as due to the hf interaction between the electron spin and the nuclear spin of Nb-93. An additional hf structure due to the interaction with two equivalent Si neighbors was also observed. Ab initio supercell calculations of Nb in 4H-SiC suggest that Nb may form a complex with a C-vacancy (V-C) resulting in an asymmetric split-vacancy (ASV) defect, Nb-Si-V-C. Combining results from EPR and supercell calculations, we assign the observed Nb-related EPR center to the hexagonal-hexagonal configuration of the AVS defect in the neutral charge state, (Nb-Si-V-C)(0).

  • 27.
    Trinh, Xuan Thang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Szasz, K.
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary.
    Hornos, T.
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary.
    Kawahara, K.
    Institute of Physics, Loránd Eötvös University, Hungary.
    Suda, J.
    Institute of Physics, Loránd Eötvös University, Hungary.
    Kimoto, T.
    Institute of Physics, Loránd Eötvös University, Hungary.
    Gali, Ádam
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary, Department of Electronic Science and Engineering, Kyoto University, Japan.
    Janzén, Erik
    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.
    Identification of the negative carbon vacancy at quasi-cubic site in 4H-SiC by EPR and theoretical calculations2014In: Silicon Carbide and Related Materials 2013, PTS 1 AND 2, Trans Tech Publications Inc., 2014, Vol. 778-780, p. 285-288Conference paper (Refereed)
    Abstract [en]

    In freestanding n-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site, V-C(-)(h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site, V-C(-)(k). The identification is further supported by hyperfine calculations.

1 - 27 of 27
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