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  • 1. Henry, A.
    et al.
    Janson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janzen, E.
    Properties of the bound excitons associated to the 3838 angstrom line in 4H-SiC and the 4182 angstrom line in 6H-SiC2004In: SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2 / [ed] Madar, R; Camassel, J, 2004, Vol. 457-460, p. 549-554Conference paper (Refereed)
    Abstract [en]

    We report the results of a photoluminescence (PL) study of the properties of a bound-exciton (BE) line observed at about 3838Angstrom in the PL spectrum of 4H-SiC and at 4182Angstrom in 6H-SiC. Both spectra have almost the same phonon structure containing localized modes. The temperature dependences show that the no-phonon (NP) lines have at least three excited states higher in energy. The most intense high-temperature lines do not split under applied magnetic field whereas the low temperature lines split into three components when the magnetic field is applied in the direction perpendicular to the c-axis. Time-resolved PL reveals several hundreds microseconds long lifetime at 2K with a second component an order of magnitude faster. Our results can be explained by an excitonic recombination at an isoelectronic center but are in conflict with the previous association of the 3838Angstrom line in 4H-SiC with the recombination of the bound exciton at the neutral shallow boron acceptor. The luminescence in our samples is increasing with excitation time. This luminescence is not observed from our as-grown material but appears after SIMS analysis. The as-grown material used was intentionally boron-doped epilayers.

  • 2.
    Janson, Martin S.
    et al.
    KTH, Superseded Departments, Electronics.
    Hallén, Anders
    KTH, Superseded Departments, Electronics.
    Linnarsson, Margareta K
    KTH, Superseded Departments, Electronics.
    Svensson, Bengt Gunnar
    KTH, Superseded Departments, Electronics.
    Nordell, Nils
    IMC, Sweden.
    Karlsson, S.
    Electric-field-assisted migration and accumulation of hydrogen in silicon carbide2000In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 61, no 11, p. 7195-7198Article in journal (Refereed)
    Abstract [en]

    The diffusion of deuterium (H-2) in epitaxial 4H-SiC layers with buried highly Al-acceptor doped regions has been studied by secondary ion mass spectrometry. H-2 was introduced in the near surface region by the use of 20-keV implantation after which the samples were thermally annealed. As a result, an anomalous accumulation of H-2 in the high doped layers was observed. To explain the accumulation kinetics, a model is proposed where positively charged H-2 ions are driven into the high doped layer and become trapped there by the strong electric field at the edges. This effect is important for other semiconductors as well, since hydrogen is a common impurity present at high concentrations in many semiconductors.

  • 3.
    Janson, Martin S.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Svensson, Bengt G.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Electronic stopping cross sections in silicon carbide for low-velocity ions with 1 <= Z(1)<= 152004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, no 1, p. 164-169Article in journal (Refereed)
    Abstract [en]

    The mean projected range R-p for a large number of H-1, H-2, Li-7, B-11, N-14, O-16, Al-27, and P-31 implantations into SiC with ion energies ranging from 0.5 keV to 4 MeV are investigated. From the R-p data the electronic stopping cross sections S-e are extracted. A plot of the extracted S-e at a fixed velocity-below the Fermi velocity of the target valence electrons-versus the ion atomic number Z(1) reveals a local maximum around Z(1)=7. Furthermore, in this velocity regime a slower than velocity-proportional energy dependence, S(e)proportional toE(0.30)-E-0.45, is found for ions with 1less than or equal toZ(1)less than or equal to8, while Al-27 and P-31 exhibit an energy dependence just above velocity-proportionality: S(e)proportional toE(0.52), for both ions. These finding are in good qualitative agreement with the low-velocity electronic stopping behavior previously reported for carbon targets.

  • 4.
    Janson, Martin S.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Svensson, Bengt G.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Achtziger, N.
    Uneus, L.
    Spetz, A. Lloyd
    Forsberg, U.
    Hydrogen in the wide bandgap semiconductor silicon carbide2004In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T108, p. 99-112Article in journal (Refereed)
    Abstract [en]

    In this paper we give a review of our recent results related to the incorporation of hydrogen (H) in silicon carbide (SiC) and its interaction with acceptor doping atoms and implantation induced defects. Hydrogen is an abundant impurity in the growth of epitaxial SiC since it is present in the precursor gases and since H-2 is used as the carrier gas. High concentrations of hydrogen are indeed incorporated into highly doped p-type epi-layers and it is shown that the main source is the carrier gas. Furthermore, it is revealed that the entire substrate becomes homogeneously filled with hydrogen during growth and that this hydrogen is more thermally stable than that in the epi-layer. Incorporation of hydrogen from an H-2 ambient, at temperatures considerably lower than those used for epitaxy, is also demonstrated in p-type samples coated with a catalytic metal film. This effect is most likely the cause for the increased series resistance observed in p-type SiC Schottky sensor devices using a catalytic metal gate after annealing at 600 degrees C in a H-2 containing ambient. Hydrogen is found to passivate the acceptors Al and B by forming electrically neutral H-acceptor complexes. Unlike in Si and GaAs, the two H-acceptor complexes in SiC exhibit very different dissociation energies, suggesting that the atomic configurations of the complexes are significantly different. The migration of mobile hydrogen in the presence of externally applied, or internal built-in, electric fields further reveals that hydrogen is present as H+ in p-type SiC. Finally, the redistribution and subsequent out-diffusion of low energy implanted H-1 and H-2 is investigated. Two annealing phases for the redistribution are observed, and the activation energies for the processes are extracted.

  • 5.
    Janson, Martin S.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Slotte, J.
    Kuznetsov, Andrej Y.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Saarinen, K.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vacancy-related defect distributions in B-11-, N-14-, and Al-27-implanted 4H-SiC: Role of channeling2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 95, no 1, p. 57-63Article in journal (Refereed)
    Abstract [en]

    The defect distributions in B-11-, N-14-, and Al-27-implanted epitaxial 4H-SiC are studied using monoenergetic positron beams. At least three types of defects are needed to account for the Doppler broadening annihilation spectra and two of the defects are tentatively identified as V-Si, and VSiVC. By comparing the defect profiles extracted from the annihilation spectra to the chemical profiles determined by secondary ion mass spectrometry, and to the primary defect profiles obtained from binary collision approximation simulations, it is concluded that the defects found at depths considerably deeper than the projected range of the implanted ions mainly originate from deeply channeled ions.

  • 6.
    Linnarsson, Margareta
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Janson, Martin S.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Forsberg, U.
    Janzen, E.
    In-diffusion, trapping and out-diffusion of deuterium in 4H-SiC substrates2006In: Silicon Carbide and Related Materials 2005, Pts 1 and 2 / [ed] Devaty, RP, 2006, Vol. 527-529, p. 637-640Conference paper (Refereed)
    Abstract [en]

    Incorporation of hydrogen/deuterium in n-, p-type, and semi-insulating 4H-SiC substrates during epitaxial growth at 1590 degrees C has been studied in detail by secondary ion mass spectrometry. Out-diffusion has been investigated in samples subsequently annealed at high temperatures. After the epitaxial growth, deuterium is detected throughout the entire substrates. Out-diffusion can be observed after anneals at 1300 degrees C, but traces of deuterium can still be found in samples annealed as high as 1700 degrees C. A trap limited diffusion mechanism is proposed with vacancy related hydrogen trapping centers in n-type and semi insulating 4H-SiC substrates.

  • 7.
    Linnarsson, Margareta K.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Janson, Martin S.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nordell, Nils
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Wong-Leung, J.
    Schoner, A.
    Formation of precipitates in heavily boron doped 4H-SiC2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5316-5320Article in journal (Refereed)
    Abstract [en]

    Secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) are utilized to study precipitation and the solubility of B in 4H-SiC epitaxial layers super saturated with B. Heat treatments are performed in Ar atmosphere in an rf-heated furnace at temperatures between 1700 and 2000 degrees C. SIMS ion images, and TEM micrographs reveal the formation of two types of precipitates where the larger, more thermally stable one is suggested to be B4C. The boron solubility is determined from SIMS depth profiles and is shown to follow the Arrhenius expression: 7.1 x 10(22) exp(-1.4 eV/k(B)T) cm(-3) over the studied temperature range.

  • 8.
    Linnarsson, Margareta K.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janson, Martin S.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Shöner, A.
    Konstantinov, A.
    Svensson, B.G.
    Boron diffusion in intrinsic, n-type and p-type 4H-SiC2004In: SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2 / [ed] Madar, R; Camassel, J, 2004, Vol. 457-460, p. 917-920Conference paper (Refereed)
    Abstract [en]

    The diffusion of boron in 4H-SiC has been studied by secondary ion mass spectrometry. Three kinds of epitaxial layers have been used, highly p-type, highly n-type and low doped n-type (intrinsic). A boron diffusion source has been introduced in the samples by ion implantation. Subsequent anneals have been carried out in Ar atmosphere in a RF-heated furnace between 1220degreesC and 2000degreesC for 5 min to 3 h. For the boron diffusion in the highly p-doped layer, 4x10(19) Al atoms/cm(3) an activation energy of 5.3 eV has been determined. A similar activation energy has been extracted in the highly n-doped layer, 1x10(19) N atoms/cm(3), although the absolute diffusivity values differ by four orders of magnitude. In the lightly n-doped layer, transient enhanced boron diffusion is observed at intrinsic conditions.

  • 9.
    Linnarsson, Margareta K.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janson, Martin S.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zhang, J.
    Janzen, E.
    Svensson, B. G.
    Self-diffusion of C-12 and C-13 in intrinsic 4H-SiC2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 95, no 12, p. 8469-8471Article in journal (Refereed)
    Abstract [en]

    Self-diffusion of carbon (C-12 and C-13) in low-doped (intrinsic) 4H-SiC has been studied using secondary ion mass spectrometry. A two layer C-13 enriched structure with C-13/C-12 ratios of 0.01 and 0.1, respectively, have been prepared by vapor phase epitaxy. Subsequent anneals have been carried out in Ar atmosphere in a rf heated furnace between 2100 and 2350 degreesC for 15 min-40 h. The C-13 depth profiles reveal a strict roott evolution for the diffusion, and the extracted carbon self-diffusion coefficients closely follow an Arrhenius temperature dependence: D-*=8.4x10(2) exp(-8.50 eV/kT) cm(2)/s. The extracted D-* are found to be 5 orders of magnitude lower than previously reported for the same temperatures in C-14 radio-tracer experiments.

  • 10. Svensson, B.G.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wong-Leung, J.
    Janson, Martin S.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linnarsson, Margareta
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kuznetsov, A. Yu.
    Alfieri, G.
    Grossner, U.
    Monakhov, E.V.
    Kortegaard Nielsen, Hanne
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jagadish, C.
    Grillenberger, J.
    Ion implantation processing and related effects in SiC2006In: Silicon Carbide and Related Materials 2005, Pts 1 and 2 / [ed] Devaty, RP, 2006, Vol. 527-529, p. 781-786Conference paper (Refereed)
    Abstract [en]

    A brief survey is given of some recent progress regarding ion implantation processing and related effects in 4H- and 6H-SiC. Four topics are discussed; an empirical ion range distribution simulator, dynamic defect annealing during implantation, formation of highly p(+)-doped layers, and deactivation of N donors by ion-induced defects.

  • 11. Wong-Leung, J.
    et al.
    Janson, Martin S.
    KTH, School of Information and Communication Technology (ICT).
    Kuznetsov, A.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Jagadish, C.
    Cockayne, D. J. H.
    Ion implantation in 4H-SiC2008In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 266, no 8, p. 1367-1372Article in journal (Refereed)
    Abstract [en]

    Silicon carbide offers unique applications as a wide bandgap semiconductor. This paper reviews various aspects of ion implantation in 4H-SiC studied with a view to optimise ion implantation in silicon carbide. Al, P and Si ions with keV energies were used. Channelling effects were studied in both a-axis and c-axis crystals as a function of tilts along major orthogonal planes and off the major orthogonal planes. Major axes such as [0 0 0 1] and the [ 1 1 (2) over bar 0] and minor axis like the [1 1 (2) over bar 3] showed long channelling tails and optimum tilts for minimising channelling are recommended. TEM analyses of the samples showed the formation of (0 0 0 1) prismatic loops and the (1 1 (2) over bar 0) loops as well,in both a and c-cut crystals. We also note the presence of voids only in P implanted samples implanted with amorphising doses. The competing process between damage accumulation and dynamic annealing was studied by determining the critical temperature for the transition between crystalline and amorphous SiC and an activation energy of 1.3 eV is extracted.

  • 12. Zhang, Y.
    et al.
    Weber, W. J.
    Jiang, W.
    Shutthanandan, V.
    Thevuthasan, S.
    Janson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Annealing behavior of Al-implantation-induced disorder in 4H-SiC2004In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 219, p. 647-651Article in journal (Refereed)
    Abstract [en]

    Single crystal 4H-SiC films were implanted at 150 K with 1.1 MeV Al-2(2+) and subsequently annealed at elevated 2 temperatures. In addition to the damage peak, an enhancement of the backscattering yield between the surface peak and damage peak is observed. Rutherford backscattering spectrometry results indicate that the relative Si disorder at the damage peak recovers significantly as the annealing temperature increases, and the near-surface peak disappears after annealing at 570 K. However, the residual Si disorder is more resistant to high-temperature annealing in the region of the implanted Al. The maximum concentration of Al profile measured by secondary ion mass spectroscopy is a factor of 1000 lower than the level of the residual Si disorder at the same region. Analysis of these results indicates that the excess residual Si disorder around the implanted Al projected range cannot be accounted for by just the Al interstitials; instead, it appears that implanted Al stabilizes or inhibits recovery Si disorder under the current experimental conditions.

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