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  • 1. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 19, p. 2908-2910Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.

  • 2. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 184, no 04-jan, p. 263-267Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.

  • 3. Alfieri, G.
    et al.
    Monakhov, E. V.
    Svensson, B. G.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Defect energy levels in hydrogen-implanted and electron-irradiated n-type 4H silicon carbide2005In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, no 11Article in journal (Refereed)
    Abstract [en]

    Using deep level transient spectroscopy (DLTS), we have studied the energy position and thermal stability of deep levels in nitrogen doped 4H-SiC epitaxial layers after 1.2 MeV proton implantation and 15 MeV electron irradiation. Isochronal annealing was performed at temperatures from 100 to 1200 degrees C in steps of 50 degrees C. The DLTS measurements, which were carried out in the temperature range from 120 to 630 K after each annealing step, reveal the presence of ten electron traps located in the energy range of 0.45-1.6 eV below the conduction band edge (E-c). Of these ten levels, three traps at 0.69, 0.73, and 1.03 eV below E-c, respectively, are observed only after proton implantation. Dose dependence and depth profiling studies of these levels have been performed. Comparing the experimental data with computer simulations of the implantation and defects profiles, it is suggested that these three new levels, not previously reported in the literature, are hydrogen related. In particular, the E-c-0.73 eV level displays a very narrow depth distribution, confined within the implantation profile, and it originates most likely from a defect involving only one H atom.

  • 4. Audren, A.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Linnarsson, Margareta K.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Possnert, G.
    Damage recovery in ZnO by post-implantation annealing2010In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 268, no 11-12, p. 1842-1846Article in journal (Other academic)
    Abstract [en]

    ZnO bulk samples were implanted with 200 key-Co ions at room temperature with two fluences, 1 x 10(16) and 8 x 10(16) cm(-2), and then annealed in air for 30 min at different temperatures up to 900 degrees C. After the implantation and each annealing step, the samples were analyzed by Rutherford backscattering spectrometry (RBS) in random and channeling directions to follow the evolution of the disorder profile. The RBS spectra reveal that disorder is created during implantation in proportion to the Co fluence. The thermal treatments induce a disorder recovery, which is however, not complete after annealing at 900 degrees C, where about 15% of the damage remains. To study the Co profile evolution during annealing, the samples were, in addition to RBS, characterized by secondary ion mass spectrometry (SIMS). The results show that Co diffusion starts at 800 degrees C, but also that a very different behavior is seen for Co concentrations below and above the solubility limit. (C) 2010 Elsevier B.V. All rights reserved.

  • 5. Audren, A.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Possnert, G.
    Damage recovery in the oxygen sublattice of ZnO by post-implantation annealing2012In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 272, p. 418-421Article in journal (Refereed)
    Abstract [en]

    Hydrothermally grown zinc oxide bulk samples were implanted with 200 key-Co ions with a fluence of 4.5 x 10(16) cm(-2) and then annealed in air during 30 min at different temperatures up to 900 degrees C. After the implantation and each annealing step, the samples were analyzed using the nuclear reaction O-16(alpha,alpha)O-16 at 3.045 MeV He in random and channeling directions to follow the annealing of the disorder profile in the O sublattice. For comparison, the disorder in the Zn sublattice was also observed by Rutherford backscattering spectrometry (RBS) in random and channeling directions. The results reveal that the disorder created during the Co implantation is slightly higher in the O sublattice than in the Zn sublattice. The disorder recovery induced by the thermal treatments, starts at 500 degrees C in the O sublattice and at 700 degrees C in the Zn sublattice. Although, the most part of the disorder recovery occurs between 700 and 800 degrees C in both sublattices.

  • 6. Ayedh, H. M.
    et al.
    Bobal, V.
    Nipoti, R.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Formation and annihilation of carbon vacancies in 4H-SiC2016In: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015, Trans Tech Publications, 2016, p. 331-336Conference paper (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is a major point defect in high-purity 4H-SiC epitaxial layers limiting the minority charge carrier lifetime. In layers grown by chemical vapor deposition techniques, the VC concentration is typically in the range of 1012 cm-3 and after device processing at temperatures approaching 2000 °C, it can be enhanced by several orders of magnitude. In the present contribution, we show that the cooling rate after high-temperature processing has a profound influence on the resulting VC concentration where a slow rate promotes elimination of VC. Further, isochronal annealing of as-grown and as-oxidized epi-layers protected by a carbon-cap was undertaken between 800 °C and 1600 °C. The results reveal that thermodynamic equilibrium of VC is established rather rapidly at moderate temperatures, reaching a VC concentration of only a few times 1011 cm-3 after 40 min at 1500 °C. Hence, the concept of eliminating VC’s by annealing at moderate temperatures under C-rich equilibrium conditions shows great promise and enables reannealing of high-temperature processed wafers, in contrast to the procedures commonly used today to eliminate VC. In-diffusion of carbon interstitials and out-diffusion of VC’s are discussed as the kinetics processes establishing the thermodynamic equilibrium.

  • 7. Ayedh, H. M.
    et al.
    Bobal, V.
    Nipoti, R.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Formation of carbon vacancy in 4H silicon carbide during high-temperature processing2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 1, p. 012005-Article in journal (Refereed)
    Abstract [en]

    As-grown and pre-oxidized silicon carbide (SiC) samples of polytype 4H have been annealed at temperatures up to 1950 degrees C for 10 min duration using inductive heating, or at 2000 degrees C for 30 s using microwave heating. The samples consisted of a n-type high-purity epitaxial layer grown on 4 degrees off-axis < 0001 > n(+)-substrate and the evolution of the carbon vacancy (V-C) concentration in the epitaxial layer was monitored by deep level transient spectroscopy via the characteristic Z(1/2) peak. Z(1/2) appears at similar to 0.7 eV below the conduction band edge and arises from the doubly negative charge state of V-C. The concentration of V-C increases strongly after treatment at temperatures >= 1600 degrees C and it reaches almost 10(15)cm(-3) after the inductive heating at 1950 degrees C. A formation enthalpy of similar to 5.0 eV is deduced for V-C, in close agreement with recent theoretical predictions in the literature, and the entropy factor is found to be similar to 5 k (k denotes Boltzmann's constant). The latter value indicates substantial lattice relaxation around V-C, consistent with V-C being a negative-U system exhibiting considerable Jahn-Teller distortion. The microwave heated samples show evidence of non-equilibrium conditions due to the short duration used and display a lower content of V-C than the inductively heated ones. Finally, concentration-versus-depth profiles of V-C favour formation in the "bulk" of the epitaxial layer as the prevailing process and not a Schottky type process at the surface.

  • 8. Ayedh, H. M.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Elimination of carbon vacancies in 4H-SiC epi-layers by near-surface ion implantation: Influence of the ion species2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 17, article id 175701Article in journal (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is a prevailing point defect in high-purity 4H-SiC epitaxial layers, and it plays a decisive role in controlling the charge carrier lifetime. One concept of reducing the VC-concentration is based on carbon self-ion implantation in a near surface layer followed by thermal annealing. This leads to injection of carbon interstitials (Ci's) and annihilation of VC's in the epi-layer "bulk". Here, we show that the excess of C atoms introduced by the self-ion implantation plays a negligible role in the VC annihilation. Actually, employing normalized implantation conditions with respect to displaced C atoms, other heavier ions like Al and Si are found to be more efficient in annihilating VC's. Concentrations of VC below ∼2 × 1011 cm-3 can be reached already after annealing at 1400 °C, as monitored by deep-level transient spectroscopy. This corresponds to a reduction in the VC-concentration by about a factor of 40 relative to the as-grown state of the epi-layers studied. The negligible role of the implanted species itself can be understood from simulation results showing that the concentration of displaced C atoms exceeds the concentration of implanted species by two to three orders of magnitude. The higher efficiency for Al and Si ions is attributed to the generation of collision cascades with a sufficiently high energy density to promote Ci-clustering and reduce dynamic defect annealing. These Ci-related clusters will subsequently dissolve during the post-implant annealing giving rise to enhanced Ci injection. However, at annealing temperatures above 1500 °C, thermodynamic equilibrium conditions start to apply for the VC-concentration, which limit the net effect of the Ci injection, and a competition between the two processes occurs.

  • 9. Ayedh, H. M.
    et al.
    Nipoti, R.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Controlling the carbon vacancy concentration in 4H-SiC subjected to high temperature treatment2016In: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015, Trans Tech Publications, 2016, p. 414-417Conference paper (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is the major charge carrier lifetime limiting-defect in 4H-SiC epitaxial layers and it is readily formed during elevated heat treatments. Here we describe two ways for controlling the VC concentration in 4H-SiC epi-layer using different annealing procedures. One set of samples was subjected to high temperature processing at 1950 °C for 3 min, but then different cooling rates were applied. A significant reduction of the VC concentration was demonstrated by the slow cooling rate. In addition, elimination of the VC’s was also established by annealing a sample, containing high VC concentration, at 1500 °C for a sufficiently long time. Both procedures clearly demonstrate the need for maintaining thermodynamic equilibrium during cooling.

  • 10. Ayedh, H. M.
    et al.
    Nipoti, R.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Elimination of carbon vacancies in 4H-SiC employing thermodynamic equilibrium conditions at moderate temperatures2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 25Article in journal (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is a major point defect in high-purity 4H-SiC epitaxial layers limiting the minority charge carrier lifetime. In layers grown by chemical vapor deposition techniques, the VC concentration is typically in the range of 1012cm-3, and after device processing at temperatures approaching 2000 °C, it can be enhanced by several orders of magnitude. In the present study, both as-grown layers and a high-temperature processed one have been annealed at 1500 °C and the VC concentration is demonstrated to be strongly reduced, exhibiting a value of only a few times 1011cm-3 as determined by deep-level transient spectroscopy measurements. The value is reached already after annealing times on the order of 1 h and is evidenced to reflect thermodynamic equilibrium under C-rich ambient conditions. The physical processes controlling the kinetics for establishment of the VC equilibrium are estimated to have an activation energy below ∼3 eV and both in-diffusion of carbon interstitials and out-diffusion of VC’s are discussed as candidates. This concept of VC elimination is flexible and readily integrated in a materials and device processing sequence.

  • 11. Ayedh, H. M.
    et al.
    Nipoti, R.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Svensson, B. G.
    Thermodynamic equilibration of the carbon vacancy in 4H-SiC: A lifetime limiting defect2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 122, no 2, article id 025701Article in journal (Refereed)
    Abstract [en]

    The carbon vacancy (V-C) is a prominent defect in as-grown 4H-SiC epitaxial layers for high power bipolar devices. V-C is electrically active with several deep levels in the bandgap, and it is an efficient "killer" of the minority carrier lifetime in n-type layers, limiting device performance. In this study, we provide new insight into the equilibration kinetics of the thermodynamic processes governing the V-C concentration and how these processes can be tailored. A slow cooling rate after heat treatment at similar to 2000 degrees C, typically employed to activate dopants in 4H-SiC, is shown to yield a strong reduction of the V-C concentration relative to that for a fast rate. Further, post-growth heat treatment of epitaxial layers has been conducted over a wide temperature range (800-1600 degrees C) under C-rich surface conditions. It is found that the thermodynamic equilibration of V-C at 1500 degrees C requires a duration less than 1 h resulting in a V-C concentration of only similar to 10(11) cm(-3), which is, indeed, beneficial for high voltage devices. In order to elucidate the physical processes controlling the equilibration of V-C, a defect kinetics model is put forward. The model assumes Frenkel pair generation, injection of carbon interstitials (C-i's) from the C-rich surface (followed by recombination with V-C's), and diffusion of V-C's towards the surface as the major processes during the equilibration, and it exhibits good quantitative agreement with experiment.

  • 12. Azarov, A. Yu.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Du, X. L.
    Liu, Z. L.
    Svensson, B. G.
    Kuznetsov, A. Yu.
    Thermally induced surface instability in ion-implanted Mg(x)Zn(1-x)O films2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 1, p. 014114-Article in journal (Refereed)
    Abstract [en]
    Thermal stability of originally single crystalline wurtzite Mg(x)Zn(1-x)O (x <= 0.3) films implanted at room temperature with (166)Er ions is studied by a combination of Rutherford backscattering spectrometry, time-of-flight elastic recoil detection analysis, x-ray diffraction analysis, and atomic force microscopy. The MgZnO films exhibit a complex behavior during postimplantation annealing associated with compositional changes and surface erosion in addition to Er accumulation at the surface. The importance of these processes depends on the Mg content, annealing temperature, and amount of implantation damage. Specifically, increases in the Mg content as well as the implantation damage enhance the compositional changes in the near-surface region and give rise to altered stoichiometry and Mg-enriched phase separation. In its turn, the rate of surface erosion in MgZnO under the thermal treatment depends on temperature, MgZnO composition, and the amount of implantation damage nontrivially, which is attributed to the compositional changes in the near-surface region assisted by the implantation damage.
  • 13. Azarov, A. Yu
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Du, X. L.
    Rauwel, P.
    Kuznetsov, A. Yu.
    Svensson, B. G.
    Effect of implanted species on thermal evolution of ion-induced defects in ZnO2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 7, p. 073512-Article in journal (Refereed)
    Abstract [en]

    Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from B-11 to Bi-209) to ion doses up to 2 x 10(16) cm(-2). The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 degrees C, while co-implantation with B (via BF2) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures similar to 500 degrees C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 degrees C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability.

  • 14. Azarov, A. Yu.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Du, X. L.
    Kuznetsov, A. Yu.
    Damage accumulation and annealing behavior in high fluence implanted MgZnO2012In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 272, p. 426-429Article in journal (Refereed)
    Abstract [en]

    Molecular beam epitaxy grown MgxZn1-xO (x <= 0.3) layers were implanted at room temperature with 150 keV Er-166(+) ions in a fluence range of 5 x 10(15-)3 x 10(16) cm(-2). Evolution of ion-induced damage and structural changes were studied by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis and time-of-flight elastic recoil detection analysis. Results show that damage production enhances in both Zn- and O-sublattices with increasing the Mg content in the MgZnO. However, MgZnO as well as pure ZnO exhibits a high degree of dynamic annealing and MgZnO can not be amorphized even at the highest ion fluence used. Annealing of heavily damaged ZnO leads to a strong surface erosion and thinning of the film. Increasing the Mg content suppresses the surface evaporation in high fluence implanted MgZnO but leads to a strong surface decomposition accompanied with a Mg-rich surface layer formation during post-implantation annealing.

  • 15. Azarov, A. Yu
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Kuznetsov, A. Yu
    Annealing of ion implanted CdZnO2012In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 45, no 23, p. 235304-Article in journal (Refereed)
    Abstract [en]

    We have studied the effect of the Cd content on the recovery of ion-induced damage in wurtzite CdxZn1-xO (x <= 0.05) films and compared with that in pure wurtzite ZnO and rock-salt CdO.200 keV Au+ and 55 keV Ar+ ion implants were performed at room temperature in the dose range of 5 x 1014-6.5 x 1015 cm-2. Rutherford backscattering/channelling spectrometry was used to characterize the damage evolution in the course of annealing (600-900 degrees C in air). A complex defect annealing behaviour is revealed in CdZnO as a function of annealing temperature, Cd content and ion dose. In particular, defects in the low dose implanted CdZnO films can be effectively removed at 800 degrees C, while the high dose implantation results in the formation of defects stable at least up to 900 degrees C. Moreover, annealing of the CdZnO films is accompanied by Cd loss at the surface for temperatures exceeding 800 degrees C. In contrast, CdO exhibits a typical damage accumulation behaviour for metals and semiconductors with high degree of ionicity, resulting in saturation and extended defect formation at high ion doses. These extended defects in pure ZnO and CdO, formed either directly during implantation or by reconstruction during post-implant annealing, are substantially more stable compared with small defects which can be efficiently removed at 700 degrees C and 600 degrees C for ZnO and CdO, respectively.

  • 16. Azarov, A. Yu
    et al.
    Jensen, J.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Aggerstam, T.
    Dopant distribution in high fluence Fe implanted GaN2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, no 5Article in journal (Refereed)
    Abstract [en]

    Undoped wurtzite GaN epilayers implanted at room temperature with 50-325 keV Fe+ ions in the fluence range of 10(15)-10(17) ions/cm(2) are studied by a combination of Rutherford backscattering/channeling spectrometry and time-of-flight elastic recoil detection analysis. The results show an enhanced Fe concentration close to the surface for high ion fluences (>1 X 10(16) cm(-2)), which increases with the ion fluence. Annealing at 800 degrees C for 30 min has a negligible effect on the Fe distribution in the material bulk, but further increases the Fe concentration near the surface. Our findings can be understood by radiation enhanced diffusion during ion implantation and an increased Fe diffusivity in the near surface region with distorted stoichiometry, or formation of secondary phases and precipitates for the highest doses. The simulation shows that, if enhanced diffusion is the reason for Fe buildup at the surface, both radiation enhanced diffusion and the thermal diffusion of Fe atoms near the surface, need to be at least five times larger than ordinary bulk diffusion to explain the increased Fe surface concentration.

  • 17. Azarov, A. Yu.
    et al.
    Svensson, B. G.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Du, X. L.
    Kuznetsov, A. Yu.
    Effect of composition on damage accumulation in ternary ZnO-based oxides implanted with heavy ions2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 3, p. 033509-Article in journal (Refereed)
    Abstract [en]

    Thin films of wurtzite MgxZn1-xO (x <= 0.3) grown by molecular beam epitaxy and wurtzite CdxZn1-xO (x <= 0.05) grown by metal organic chemical vapor deposition were implanted at room temperature with 150 keV Er+ ions and 200 keV Au+ ions in a wide dose range. Damage accumulation was studied by Rutherford backscattering/channeling spectrometry. Results show that the film composition affects the damage accumulation behavior in both MgZnO and CdZnO dramatically. In particular, increasing the Mg content in MgZnO results in enhanced damage accumulation in the region between the bulk and surface damage peaks characteristically distinguished in the pure ZnO. However, the overall damage accumulation in MgZnO layers, as well as in pure ZnO, exhibits saturation with increasing ion dose and MgZnO cannot be amorphized even at the highest ion dose used (3 X 10(16) Er/cm(2)). Increasing the Cd content in CdZnO affects the saturation stage of the damage accumulation and leads to an enhancement of damage production in both Cd and Zn sublattices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467532]

  • 18. Azarov, A. Yu.
    et al.
    Titov, A. I.
    Karaseov, P. A.
    Kucheyev, S. O.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Kuznetsov, A. Yu.
    Svensson, B. G.
    Pathak, A. P.
    Structural damage in ZnO bombarded by heavy ions2010In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 84, no 8, p. 1058-1061Article in journal (Refereed)
    Abstract [en]

    The effect of implantation parameters on damage build-up in ZnO bombarded with Bi and Er ions is studied by Rutherford backscattering/channelling spectrometry. The results show that the damage accumulation behaviour in ZnO is different dramatically from that in other semiconductors. In particular, a variation of implantation parameters, such as collision cascade density, sample temperature and ion flux, has only a minor influence on the damage accumulation in the crystal bulk for the case of such heavy ions. Moreover, an intermediate damage peak, between the surface and bulk defect peaks, is observed for all the irradiation conditions studied. The cascade density affects the behaviour of this intermediate peak with increasing ion dose.

  • 19. Azarov, Alexander
    et al.
    Rauwel, Protima
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Elektronics, Integrated devices and circuits.
    Monakhov, Edouard
    Svensson, Bengt G.
    Extended defects in ZnO: Efficient sinks for point defects2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 2, article id 022103Article in journal (Refereed)
    Abstract [en]

    Dopant-defect reactions dominate the defect formation in mono-crystalline ZnO samples implanted with Ag and B ions. This is in contrast to most other ion species studied and results in an enhanced concentration of extended defects, such as stacking faults and defect clusters. Using a combination of B and Ag implants and diffusion of residual Li atoms as a tracer, we demonstrate that extended defects in ZnO act as efficient traps for highly mobile Zn interstitials. The results imply that dynamic annealing involving interaction of point defects with extended ones can play a key role in the disorder saturation observed for ZnO and other radiation-hard semiconductors implanted with high doses.

  • 20.
    Azarov, Alexander
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Titov, A. I.
    Karaseov, P. A.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Effect of collision cascade density on radiation damage in SiC2009In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 267, no 8-9, p. 1247-1250Article in journal (Refereed)
    Abstract [en]

    The damage accumulation in 6H-SiC bombarded at room temperature with 1.3 keV/amu atomic P+ ions and small cluster ions PFn+ (n = 2 and 4) have been studied by Rutherford backscattering spectrometry in channeling mode. Results show that collision cascade density strongly affects damage buildup in SiC. The cluster ion bombardment of SiC produces more stable defects both near the surface and in the region between the surface and bulk defect peaks than irradiation by atomic ions.

  • 21.
    Azarov, Alexander
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Zamani, Atieh
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Vines, L.
    Kuznetsov, A. Yu.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Dopant incorporation in thin strained Si layers implanted with Sb2010In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 9, p. 2474-2477Article in journal (Refereed)
    Abstract [en]

    The effect of tensile strain on Sb incorporation in Si and its activation during post-implantation annealing has been Studied by a combination of Rutherford backscattering/channeling spectrometry, secondary ion mass spectrometry. X-ray diffraction and 4-point probe measurements Our results show that, for Sb implanted samples a tensile strain has an important role for dopant behavior Particularly, increasing the tensile strain in the Si layer from 0 to 0 8% leads to an enhancement of the fraction of incorporated Sb atoms in substitutional sites already during implantation from similar to 7 to 30% Furthermore, 0 8% strain in antimony doped Si gives similar to 20% reduction in the sheet resistance in comparison to the unstrained sample.

  • 22. Azarov, A.Yu.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Jensen, J.
    Aggerstam, Thomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    High dose Fe implantation of gan: Damage build-up and dopant redistribution2008In: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, 2008, Vol. 100, no PART 4Conference paper (Refereed)
    Abstract [en]

    Undoped GaN epilayers implanted at room temperature with 50-325 keV Fe + ions in the fluence range of 1015 - 1017 ions/cm are studied by a combination of Rutherford backscattering/channeling spectrometry and time-of-flight elastic recoil detection analysis. Results show that for high ion fluences (&gt;1 × 1016 cm-2) enhanced Fe concentration closer to the surface is observed. The Fe redistribution towards the surface increases as the ion fluence increases. Our findings are attributed to radiation enhanced diffusion during ion implantation and increasing of Fe diffusivity in the implantation-induced amorphous phase near the surface.

  • 23. Ber, B. Y.
    et al.
    Kazantsev, D. Y.
    Kalinina, E. V.
    Kovarskii, A. P.
    Kossov, V. G.
    Hallén, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Yafaev, R. R.
    Determination of nitrogen in silicon carbide by secondary ion mass spectrometry2004In: Journal of Analytical Chemistry, ISSN 1061-9348, E-ISSN 1608-3199, Vol. 59, no 3, p. 250-254Article in journal (Refereed)
    Abstract [en]

    The emission of atomic and complex nitrogen ions, which are the main impurity determining the n type conduction of silicon carbide, is investigated. It is shown that, among all the secondary ions of the CxN and SixN kind (x = 0, 1, 2, 3), the (26)(CN)(-) fragment exhibits the highest ion yield. The use of an ion peak with a specified mass as an analytical signal provides a detection limit for nitrogen in SiC at a level of 10(16) cm(-3). This result is attained in measurements at high mass resolution (M/DeltaM = 7500, interference peak (26)(C-13(2))(-)).

  • 24. Blank, T. V.
    et al.
    Goldberg, Y. A.
    Kalinina, E. V.
    Konstantinov, O. V.
    Konstantinov, A. O.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Temperature dependence of the photoelectric conversion quantum efficiency of 4H-SiC Schottky UV photodetectors2005In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 20, no 8, p. 710-715Article in journal (Refereed)
    Abstract [en]

    Ultraviolet Schottky photodetectors based on n-4H-SiC (N-d - N-a = 4 x 10(15) cm(-3)) epitaxial layers of high purity have been fabricated. Their spectral sensitivity range is 3.2-5.3 eV peaking at 4.9 eV (quantum efficiency is about similar to 0.3 electron/photon), which is close to the bactericidal ultraviolet radiation spectrum. The temperature dependence of the quantum efficiency of 4H-SiC Schottky structure has been investigated to determine the temperature stability and the mechanism of the photoelectric conversion process. At low temperatures (78-175 K) the quantum efficiency increases with increasing temperature for all photon energy values and then tends to saturate. We suppose that some imperfections in the space-charge region act as traps that capture both photoelectrons and photoholes. After some time the trapped electron-hole pairs recombine due to the tunnelling effect. At high temperatures (more than 300 K), the second enhancement region of the quantum efficiency is observed in the photon energy range of 3.2-4.5 eV. It is connected with a phonon contribution to indirect optical transitions between the valence band and the M-point of the conduction band. When the photon energy is close to a direct optical transition threshold this enhancement region disappears. This threshold is estimated to be 4.9 eV. At photon energies more than 5 eV a drastic fall of the quantum efficiency has been observed throughout the temperature interval. We propose that in this case the photoelectrons and photoholes are bound to form hot excitons in the space-charge region due to the Brillouin zone singularity, and do not contribute to the following photoelectroconversion process.

  • 25. Blank, T. V.
    et al.
    Gol'dberg, Y. A.
    Kalinina, E. V.
    Konstantinov, O. V.
    Konstantinov, A. O.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Temperature dependence of the quantum efficiency of 4H-SiC-Based Schottky photodiodes2001In: Technical physics letters, ISSN 1063-7850, E-ISSN 1090-6533, Vol. 27, no 9, p. 776-778Article in journal (Refereed)
    Abstract [en]

    Using metal-semiconductor structures based on a pure epitaxial layer of n-4H-SiC (N-d - N-a = 4 x 10(15) cm(-3)), UV photodetectors were created with a maximum photosensitivity at 4.9 eV and a quantum efficiency up to 0.3 el/ph. The photosensitivity spectrum of the base structure is close to the spectrum of bactericidal action of the UV radiation. For photon energies in the 3.4 - 4.7 eV range, the quantum efficiency of the photoelectric conversion exhibits rapid growth with the temperature above 300 K, which is explained by the participation of photons in indirect interband transitions. This growth is not manifested when the photon energy is close to the threshold energy of direct optical transitions in the nondirect-bandgap semiconductor, which allows the threshold energy to be evaluated (similar to4.9 eV).

  • 26. Booker, I. D.
    et al.
    Hassan, J.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Sveinbjörnsson, E. Ö
    Kordina, O.
    Bergman, J. P.
    Comparison of post-growth carrier lifetime improvement methods for 4H-SiC epilayers2012In: Silicon Carbide And Related Materials 2011, Pts 1 And 2, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 285-288Conference paper (Refereed)
    Abstract [en]

    We compare two methods for post-growth improvement of bulk carrier lifetime in 4H-SiC: dry oxidations and implantations with either 12C or 14N, followed by high temperature anneals in Ar atmosphere. Application of these techniques to samples cut from the same wafer/epilayer yields 2- to 11-fold lifetime increases, with the implantation/annealing technique shown to give greater maximum lifetimes. The maximum lifetimes reached are ∼5 μs after 12C implantation at 600 °C and annealing in Ar for 180 minutes at 1500 °C. At higher annealing temperatures the lifetimes decreases, a result which differs from reports in the literature.

  • 27. Borseth, T. M.
    et al.
    Christensen, J. S.
    Maknys, K.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Svensson, B. G.
    Kuznetsov, A. Y.
    Annealing study of Sb+ and Al+ ion-implanted ZnO2005In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 38, no 4-6, p. 464-471Article in journal (Refereed)
    Abstract [en]

    In this work we have studied diffusion and electrical activation in Al+ and Sb+ implanted ZnO samples using secondary ion mass spectrometry (SIMS), scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM). The samples were hydrothermally grown and post-implant annealing was performed at 800, 900 and 1000 degrees C in pure oxygen atmosphere, After each annealing step the samples were characterized with SSRM/SCM and SIMS. The thermal treatments did not induce any significant impurity redistribution as measured by SIMS, while electrical compensation is observed by SSRM/SCM for the Sb-implanted sample yielding less n-doping than in the as-grown samples. In the Al-implanted samples, an increase in carrier concentration is observed; we ascribe this to Al-related donors and possibly interstitial lithium, a common residual impurity in the samples that have been shown to be very mobile by SIMS.

  • 28. Bratus, V. Y.
    et al.
    Petrenko, T. T.
    von Bardeleben, H. J.
    Kalinina, E. V.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vacancy-related defects in ion-beam and electron irradiated 6H-SiC2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 184, no 04-jan, p. 229-236Article in journal (Refereed)
    Abstract [en]

    A brief review is given on EPR study of irradiation-induced defects in SiC. The results of low-temperature study of Ky1 and Ky2 centers reveal for both of them the C-S symmetry, spin S = 1/2 and close coincidence of the g-tensor components. For Ky2 defect the principal values of g-tensor have been determined as g(z) = 2.0048, g(x) = 2.0022 and g(y) = 2.0037, where z and x directions reside in the (11 (2) over bar0) plane and the z-axis makes up an angle 65 degrees with the c-axis. The same residence of z- and x-axis and an angle 59 degrees are found for Ky1 center, g(z) = 2.0058, g(x) = 2.0025 and g(y) = 2.0023. A comparison of experimental and calculated hyperfine (HF) parameters is presented which suggests that Ky2 and Ky1 defects can be assigned to the positively charged carbon vacancy in 6H-SiC. The EPR study of defects created along the Al+ ion track in n-type 6H-SiC shows that lineshape, linewidth and integral intensity of the EPR signal reflect the state of damaged layer generated by ion implantation. A variation of defect density with annealing is reported and defect origin is discussed.

  • 29. Chulapakorn, T.
    et al.
    Primetzhofer, D.
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Suvanam, Sethu Saveda
    KTH, School of Information and Communication Technology (ICT).
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Impact of H-uptake by forming gas annealing and ion implantation on photoluminescence of Si-nanoparticles2018In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 215, no 3, article id 1700444Article in journal (Refereed)
    Abstract [en]

    Silicon nanoparticles (SiNPs) are formed by implanting 70 keV Si+ into a SiO2-film and subsequent thermal annealing. SiNP samples are further annealed in forming gas. Another group of samples containing SiNP is implanted by 7.5 keV H+ and subsequently annealed in N2-atmosphere at 450 °C to reduce implantation damage. Nuclear reaction analysis (NRA) is employed to establish depth profiles of the H-concentration. Enhanced hydrogen concentrations are found close to the SiO2surface, with particularly high concentrations for the as-implanted SiO2. However, no detectable uptake of hydrogen is observed by NRA for samples treated by forming gas annealing (FGA). H-concentrations detected after H-implantation follow calculated implantation profiles. Photoluminescence (PL) spectroscopy is performed at room temperature to observe the SiNP PL. Whereas FGA is found to increase PL under certain conditions, i.e., annealing at high temperatures, increasing implantation fluence of H reduces the SiNP PL. Hydrogen implantation also introduces additional defect PL. After low-temperature annealing, the SiNP PL is found to improve, but the process is not found equivalently efficient as conventional FGA.

  • 30.
    Chulapakorn, T.
    et al.
    Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden..
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Ottosson, M.
    Uppsala Univ, Dept Chem, Angstrom Lab, Inorgan Chem, POB 538, SE-75121 Uppsala, Sweden..
    Primetzhofer, D.
    Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden..
    Moro, M. V.
    Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden..
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT).
    Luminescence of silicon nanoparticles from oxygen implanted silicon2018In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 86, p. 18-22Article in journal (Refereed)
    Abstract [en]

    Oxygen with a kinetic energy of 20 keV is implanted in a silicon wafer (100) at different fluences, followed by post-implantation thermal annealing (PIA) performed at temperatures ranging from 1000 to 1200 degrees C, in order to form luminescent silicon nanoparticles (SiNPs) and also to reduce the damage induced by the implantation. As a result of this procedure, a surface SiOx layer (with 0 < x < 2) with embedded crystalline Si nanoparticles has been created. The samples yield similar luminescence in terms of peak wavelength, lifetime, and absorption as recorded from SiNPs obtained by the more conventional method of implanting silicon into silicon dioxide. The oxygen implantation profile is characterized by elastic recoil detection (ERD) technique to obtain the excess concentration of Si in a presumed SiO2 environment. The physical structure of the implanted Si wafer is examined by grazing incidence X-ray diffraction (GIXRD). Photoluminescence (PL) techniques, including PL spectroscopy, time-resolved PL (TRPL), and photoluminescence excitation (PLE) spectroscopy are carried out in order to identify the PL origin. The results show that luminescent SiNPs are formed in a Si sample implanted by oxygen with a fluence of 2 x 10(17) atoms cm(-2) and PIA at 1000 degrees C. These SiNPs have a broad size range of 6-24 nm, as evaluated from the GIXRD result. Samples implanted at a lower fluence and/or annealed at higher temperature show only weak defect-related PL. With further optimization of the SiNP luminescence, the method may offer a simple route for integration of luminescent Si in mainstream semiconductor fabrication.

  • 31. Chulapakorn, T
    et al.
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Suvanam, Sethu Saveda
    KTH, School of Information and Communication Technology (ICT).
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Primetzhofer, D
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT).
    Influence of swift heavy ion irradiation on the photoluminescence of Si-nanoparticles and defects in SiO22017In: Nanotechnology, Vol. 28, article id 375606Article in journal (Refereed)
    Abstract [en]

    The influence of swift heavy ion (SHI) irradiation on the photoluminescence (PL) of silicon nanoparticles (SiNPs) and defects in SiO2-film is investigated. SiNPs were formed by implantation of 70 keV Si+ and subsequent thermal annealing to produce optically active SiNPs and to remove implantation-induced defects. Seven different ion species with energy between 3-36 MeV and fluence from 10(11)-10(14) cm(-2) were employed for irradiation of the implanted samples prior to the thermal annealing. Induced changes in defect and SiNP PL were characterized and correlated with the specific energy loss of the employed SHIs. We find that SHI irradiation, performed before the thermal annealing process, affects both defect and SiNP PL. The change of defect and SiNP PL due to SHI irradiation is found to show a threshold-like behaviour with respect to the electronic stopping power, where a decrease in defect PL and an anticorrelated increase in SiNP PL after the subsequent thermal annealing are observed for electronic stopping exceeding 3-5 keV nm(-1). PL intensities are also compared as a function of total energy deposition and nuclear energy loss. The observed effects can be explained by ion track formation as well as a different type of annealing mechanisms active for SHI irradiation compared to the thermal annealing.

  • 32. Chulapakorn, T.
    et al.
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Suvanam, Sethu Saveda
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Linnros, Jan T.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Primetzhofer, D.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    MeV ion irradiation effects on the luminescence properties of Si-implanted SiO2-thin films2016In: Physica Status Solidi (C) Current Topics in Solid State Physics, ISSN 1862-6351, Vol. 13, no 10-12, p. 921-926Article in journal (Refereed)
    Abstract [en]

    The effects of MeV heavy ion irradiation at varying fluence and flux on excess Si, introduced in SiO2 by keV ion implantation, are investigated by photoluminescence (PL). From the PL peak wavelength (λ) and decay lifetime (τ), two PL sources are distinguished: i) quasi-direct recombination of excitons of Si-nanoparticles (SiNPs), appearing after thermal annealing (λ &gt; 720 nm, τ ∼ μs), and ii) fast-decay PL, possibly due to oxide-related defects (λ ∼ 575-690 nm, τ ∼ ns). The fast-decay PL (ii) observed before and after ion irradiation is induced by ion implantation. It is found that this fast-decay luminescence decreases for higher irradiation fluence of MeV heavy ions. After thermal annealing (forming SiNPs), the SiNP PL is reduced for samples irradiated by MeV heavy ions but found to stabilize at higher level for higher irradiation flux; the (ii) band vanishes as a result of annealing. The results are discussed in terms of the influence of electronic and nuclear stopping powers.

  • 33. Chulapakorn, T.
    et al.
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Suvanam, Sethu Saveda
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Wolff, M.
    Primetzhofer, D.
    Possnert, G.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits. Uppsala University, Sweden.
    Si-nanoparticle synthesis using ion implantation and MeV ion irradiation2015In: Physica Status Solidi (C) Current Topics in Solid State Physics, ISSN 1862-6351Article in journal (Refereed)
    Abstract [en]

    A dielectric matrix with embedded Si-nanoparticles may show strong luminescence depending on nanoparticles size, surface properties, Si-excess concentration and matrix type. Ion implantation of Si ions with energies of a few tens to hundreds of keV in a SiO<inf>2</inf> matrix followed by thermal annealing was identified as a powerful method to form such nanoparticles. The aim of the present work is to optimize the synthesis of Si-nanoparticles produced by ion implantation in SiO<inf>2</inf> by employing MeV ion irradiation as an additional annealing process. The luminescence properties are measured by spectrally resolved photoluminescence including PL lifetime measurement, while X-ray reflectometry, atomic force microscopy and ion beam analysis are used to characterize the nanoparticle formation process. The results show that the samples implanted at 20%-Si excess atomic concentration display the highest luminescence and that irradiation of 36 MeV 127I ions affects the luminosity in terms of wavelength and intensity. It is also demonstrated that the nanoparticle luminescence lifetime decreases as a function of irradiation fluence.

  • 34. David, M. L.
    et al.
    Alfieri, G.
    Monakhov, E. M.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Blanchard, C.
    Svensson, B. G.
    Barbot, J. F.
    Electrically active defects in irradiated 4H-SiC2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 95, no 9, p. 4728-4733Article in journal (Refereed)
    Abstract [en]

    4H-SiC epilayers were irradiated with either protons or electrons and electrically active defects were studied by means of deep level transient spectroscopy. Motion of defects has been found to occur at temperature as low as 350-400 K. Indeed, the application of an electric field has been found to enhance modifications in defect concentrations that can also occur during long time annealing at elevated temperature. Two levels have been revealed and labeled B and M. Two other levels, referred to as S-1 and S-2 and located at 0.40 and 0.71 eV below the conduction band edge have been studied in detail (capture cross sections, profiling, formation energy, activation energy during annealing). The S-1 and S-2 levels have been found to exhibit a one to one relation and are proposed to be two charge states of the same acceptor center, labeled the S center.

  • 35.
    Dentoni Litta, Eugenio
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hellström, Per-Erik
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Henkel, Christoph
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Valerio, Sven
    KTH, School of Information and Communication Technology (ICT).
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    High-Deposition-Rate Atomic Layer Deposition of Thulium Oxide from TmCp3 and H2O2013In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, no 11, p. D538-D542Article in journal (Refereed)
    Abstract [en]

    A novel process for atomic layer deposition of thulium oxide (Tm2O3) has been developed, employing TmCp3 as metal precursor and H2O as oxidizing agent. The use of a highly reactive oorganometallic precursor eliminates the need for a strong oxidizing agent (such as O-3) and provides a high deposition rate of similar to 1.5 angstrom/cycle. A thorough characterization of the process has been performed, identifying true ALD-type film growth in the temperature range 200-300 degrees C. The ALD process has been further investigated by extensive physical and electrical characterization of the deposited films in terms of-composition, crystalline phase, surface roughness and extraction of the dielectric constant. The films were found to be oxygen-rich Tm2O3, with low carbon impurity content at low deposition temperature and after annealing at 600 degrees C. The developed process produced polycrystalline films, with a surface roughness <1 nm RMS. Integration in MOS capacitors demonstrated well-behaved CV curves after annealing at 600 degrees C, with a relative dielectric constant of similar to 16.

  • 36. Edmondson, P. D.
    et al.
    Parish, C. M.
    Zhang, Y.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Miller, M. K.
    Helium bubble distributions in a nanostructured ferritic alloy2013In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 434, no 1-3, p. 210-216Article in journal (Refereed)
    Abstract [en]

    A 14YWT nanostructured ferritic alloy (NFA) was implanted with He + ions to fluences of 6.75 × 1021 He m-2 at 400 °C in order to simulate the effects of high He concentrations produced in advanced fission and future fusion reactors at an accelerated timescale. The He bubble size distributions associated with specific microstructural features were characterized by a combination of transmission electron microscopy and atom probe tomography. Helium bubbles were observed on grain boundaries, dislocations, and on the surfaces of nanoclusters and larger Ti(N,C) precipitates. A polydisperse distribution of bubble sizes was observed in the ferrite matrix. With the exception of He bubbles on dislocations, bubbles were observed to increase in size with increasing fluence. The combined TEM and APT data indicates that ∼4.4% of the bubbles are located on coarse precipitates, ∼12.2% at dislocations, ∼14.4% at grain boundaries, and ∼48.6% on nanoclusters, and the remainder as isolated bubbles in the ferrite matrix. The abundances of these different trapping sites, especially the nanoclusters, might reduce the availability and mobility of He, and possibly the susceptibility of these alloys to He embrittlement.

  • 37. Edmondson, P. D.
    et al.
    Parish, C. M.
    Zhang, Y.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Miller, M. K.
    Helium entrapment in a nanostructured ferritic alloy2011In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 65, no 8, p. 731-734Article in journal (Refereed)
    Abstract [en]

    A nanostructured ferritic alloy was irradiated with He+ to simulate service in a nuclear reactor and to test the hypothesis that the surface of nanoclusters is a preferential nucleation site for He bubbles. Transmission electron microscopy and atom probe tomography showed direct evidence of He bubble nucleation on the surfaces of nanoclusters and Ti(N,C) precipitates, and along grain boundaries and dislocations, thereby demonstrating an alloy design approach to improve the radiation tolerance of structural steels in the extreme environments found in nuclear reactors.

  • 38.
    Emmoth, Birger
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kreter, A.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jakubowski, M.
    Lehnen, M.
    Litnovsky, A.
    Petersson, P.
    Philipps, V.
    Possnert, G.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Schweer, B.
    Sundelin, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Unterberg, B.
    Wienhold, P.
    In-situ measurements of carbon and deuterium deposition using the fast reciprocating probe in TEXTOR2009In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 390-91, p. 179-182Article in journal (Refereed)
    Abstract [en]

    Silicon samples were exposed in the scrape-off layer of the TEXTOR plasma using a fast reciprocating probe, with the aim of studying carbon deposition and deuterium retention during Dynamic Ergodic Divertor (DED) operation. Separate samples were exposed for 300 ms at the flat-top phase of neutral beam heated discharges. The exposure conditions were varied on a shot-to-shot basis by external magnetic perturbations generated by the DED in the m/n = 3/1, DC regime, base configuration. Nuclear Reaction Analysis (NRA) was used to characterise collector sample surfaces after their exposure. Enhanced concentrations of both carbon and deuterium (C 3-10 x 10(16) at./cm(2), D 8-60 x 10(15) at./cm(2)) were found. The D/C ratio was less than unity which indicates that most of the carbon and deuterium were co-deposited. Carbon e-folding lengths of about 2 cm were found on both toroidal sides of the probe independent of DED perturbations.

  • 39. Gabrysch, Markus
    et al.
    Majdi, Saman
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Linnarsson, Margareta K
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Schoner, Adolf
    Twitchen, Daniel
    Isberg, Jan
    Compensation in boron-doped CVD diamond2008Article in journal (Refereed)
    Abstract [en]

    Hall-effect measurements on single crystal boron-doped CVD diamond in the temperature interval 80-450 K are presented together with SIMS measurements of the dopant concentration. Capacitance-voltage measurements on rectifying Schottky junctions manufactured on the boron-doped structures are also presented in this context. Evaluation of the compensating donor (N-D) and acceptor concentrations (N-A) show that in certain samples very low compensation ratios (N-D/N-A below 10(-4)) have been achieved. The influence of compensating donors on majority carrier transport and the significance for diamond device performance are briefly discussed.

  • 40. Galeckas, A.
    et al.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Majdi, S.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Pirouz, P.
    Combined photoluminescence-imaging and deep-level transient spectroscopy of recombination processes at stacking faults in 4H-SiC2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 23Article in journal (Refereed)
    Abstract [en]

    We report on electronic properties of single- and double-layer stacking faults in 4H-SiC and provide an insight into apparent distinctions of recombination-enhanced defect reactions at these faults. Photoluminescence imaging spectroscopy and deep-level transient spectroscopy experiments reveal key constituents of radiative recombination and also provide firm evidence of nonradiative centers at E-V+0.38 eV responsible for recombination-enhanced mobility of silicon-core partial dislocations. A comprehensive energy level model is proposed allowing for a qualitative description of recombination activity at different types of stacking faults and the corresponding bounding partial dislocations.

  • 41.
    Galeckas, Augustinas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallen, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schoner, A.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Pirouz, P.
    Investigation of structural stability in 4H-SiC structures with heavy ion implanted interface2006In: Silicon Carbide and Related Materials 2005, Pts 1 and 2, 2006, Vol. 527-529, p. 395-398Conference paper (Refereed)
    Abstract [en]

    We investigate the possibility of controlling formation of stacking faults (SFs) at the interface region by implanting the 4H-SiC substrate with low-energy antimony ions (75 keV Sb+) prior to conventional CVD growth of the homoepitaxial layers. This approach is based on the solidsolution hardening concept, according to which interaction of impurity atoms with dislocations makes the motion of the latter more difficult. Photoluminescence imaging spectroscopy is employed to investigate incorporation of Sb+ implants at the buried interface and also to assess its impact on structural degradation. Spectral results are analyzed considering both the onset of n-type doping and irradiation damage. The latter factor was estimated separately from supplementary measurements of high-energy (2.5 MeV H+) proton-irradiated 4H-SiC epilayers. We compare results of optically stimulated SF formation in virgin and Sb implanted regions and provide a comprehensive picture of the defect evolution, including microscopic details of the imminent nucleation sites.

  • 42.
    Galeckas, Augustinas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kortegaard Nielsen, Hanne
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Svensson, Bengt G.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Pirouz, P
    Investigation of stacking fault formation in hydrogen bombarded 4H-SiC2005In: SILICON CARBIDE AND RELATED MATERIALS 2004 / [ed] Nipoti, R; Poggi, A; Scorzoni, A, 2005, Vol. 483, p. 327-330Conference paper (Refereed)
    Abstract [en]

    The effects of hydrogen and proton irradiation on stacking fault formation in 4H-SiC are investigated by an optical pump-probe method of imaging spectroscopy. We report optically stimulated nucleation and expansion of stacking faults (SFs) in 0.6 keV H-2(+) implanted n-/n+ and p+/n-/n+ structures. The activation enthalpy for recombination enhanced dislocation glide (REDG) in hydrogenated samples (&SIM; 0.25 eV) is found to be similar to that in a virgin material. Our results indicate that SFs mainly nucleate at the internal n-/n+ interface, beyond reach of hydrogen, thus justifying minor SF passivation effect. No REDG could be initiated optically in 2.5 MeV proton irradiated samples due to radiation defects providing alternative recombination channels to bypass the REDG mechanism. The radiation damage was verified by DLTS, revealing several new levels below E-C in the range 0.4-0.80 eV, and by PL, showing the onset of D-center related luminescence band and concurrent increase of the nonradiative recombination rate.

  • 43.
    Garcia-Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Grzonka, J.
    Gilbert, M. R.
    Fortuna-Zalesna, E.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Impact of helium implantation and ion-induced damage on reflectivity of molybdenum mirrors2016In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584Article in journal (Refereed)
    Abstract [en]

    Molybdenum mirrors were irradiated with Mo and He ions to simulate the effect of neutron irradiation on diagnostic first mirrors in next-generation fusion devices. Up to 30 dpa were produced under molybdenum irradiation leading to a slight decrease of reflectivity in the near infrared range. After 3×1017 cm-2 of helium irradiation, reflectivity decreased by up to 20%. Combined irradiation by helium and molybdenum led to similar effects on reflectivity as irradiation with helium alone. Ion beam analysis showed that only 7% of the implanted helium was retained in the first 40nm layer of the mirror. The structure of the near-surface layer after irradiation was studied with scanning transmission electron microscopy and the extent and size distribution of helium bubbles was documented. The consequences of ion-induced damage on the performance of diagnostic components are discussed.

  • 44. Gulbinas, Karolis
    et al.
    Grivickas, Vytautas
    Mahabadi, Haniyeh P.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Usman, Muhammad
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Surface Recombination Investigation in Thin 4H-SiC Layers2011In: Materials Science-Medziagotyra, ISSN 1392-1320, Vol. 17, no 2, p. 119-124Article in journal (Refereed)
    Abstract [en]

    n- and p-type 4H-SiC epilayers were grown on heavily doped SiC substrates. The thickness of the p-type layer was 7 mu m and the doping level around 10(17) cm(-3), while the n-type epilayers were 15 mu m thick and had a doping concentration of 3-5x10(15) cm(-3). Several different surface treatments were then applied on the epilayers for surface passivation: SiO(2) growth, Al(2)O(3) deposited by atomic layer deposition, and Ar-ion implantation. Using collinear pump - probe technique the effective carrier lifetimes were measured from various places and statistical lifetime distributions were obtained. For surface recombination evaluation, two models are presented. One states that surface recombination velocity (SRV) is equal on both the passivation/epi layer interface (S(2)) and the deeper interface between the epilayer and the SiC substrate (S(1)), i.e. (S(1) = S(2)). The other model is simulated assuming that SRV in the epilayer/substrate (S(1)) interface is constant while in the passivation layer/epilayer (S(2)) interface SRV can be varied S(2) < S(1). Empirical nomograms are presented with various parameters sets to evaluate S(2) values. We found that on the investigated 4H-SiC surfaces S(2) ranges from 3x10(4) to 5 x 10(4) assuming that the bulk lifetime is 4 mu s. In Ar(+) implanted surfaces S(2) is between (10(5)-10(6)) cm/s.

  • 45.
    Gustafsson, Oscar
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101).
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Höglund, L.
    Karim, A.
    Noharet, B.
    Wang, Q.
    Gromov, A.
    Almqvist, S.
    Zhang, A.
    Acreo, Sweden.
    Junique, S.
    Andersson, J. Y.
    Asplund, C.
    von Würtemberg, R. Marcks
    Malm, H.
    Martijn, H.
    Long-wavelength infrared quantum-dot based interband photodetectors2011In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 54, no 3, p. 287-291Article in journal (Refereed)
    Abstract [en]

    We report on the design and fabrication of (Al)GaAs(Sb)/InAs tensile strained quantum-dot (QD) based detector material for thermal infrared imaging applications in the long-wavelength infrared (LWIR) regime. The detection is based on transitions between confined dot states and continuum states in a type-II band lineup, and we therefore refer to it as a dot-to-bulk (D2B) infrared photodetector with expected benefits including long carrier lifetime due to the type-II band alignment, suppressed Shockley-Read-Hall generation-recombination due to the relatively large-bandgap matrix material, inhibited Auger recombination processes due to the tensile strain and epitaxial simplicity. Metal-organic vapor-phase epitaxy was used to grow multiple (Al)GaAs(Sb) QD layers on InAs substrates at different QD nominal thicknesses, compositions, doping conditions and multilayer periods, and the material was characterized using atomic force and transmission electron microscopy, and Fourier-transform infrared absorption spectroscopy. Dot densities up to 1 x 10(11) cm(-2), 1 x 10(12) cm(-2) and 3 x 10(10) cm(-2) were measured for GaAs, AlGaAs and GaAsSb QDs, respectively. Strong absorption in GaAs, AlGaAs and GaAsSb multilayer QD samples was observed in the wavelength range 6-12 mu m. From the wavelength shift in the spectral absorption for samples with varying QD thickness and composition it is believed that the absorption is due to an intra- valance band transition. From this it is possible to estimate the type-II inter-band transition wavelength, thereby suggesting that (Al)GaAs(Sb) QD/InAs heterostructures are suitable candidates for LWIR detection and imaging.

  • 46.
    Hallén, Anders.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janson, M. S.
    Kuznetsov, A. Y.
    Aberg, D.
    Linnarsson, Margareta K
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Svensson, B. G.
    Persson, P. O.
    Carlsson, F. H. C.
    Storasta, L.
    Bergman, J. P.
    Sridhara, S. G.
    Zhang, Y.
    Ion implantation of silicon carbide2002In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 186, p. 186-194Article in journal (Refereed)
    Abstract [en]

    Ion implantation is an important technique for a successful implementation of commercial SiC devices. Much effort has also been devoted to optimising implantation and annealing parameters to improve the electrical device characteristics. However, there is a severe lack of understanding of the fundamental implantation process and the generation and annealing kinetics of point defects and defect complexes. Only very few of the most elementary intrinsic point defects have been unambiguously identified so far. To reach a deeper understanding of the basic mechanisms SiC samples have been implanted with a broad range of ions, energies, doses, etc., and the resulting defects and damage produced in the lattice have been studied with a multitude of characterisation techniques. In this contribution we will review some of the results generated recently and also try to indicate where more research is needed. In particular, deep level transient spectroscopy (DLTS) has been used to investigate point defects at very low doses and transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) are used for studying the damage build-up at high doses.

  • 47.
    Hallén, Anders.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Keskitalo, N.
    Defect distributions in silicon implanted with low doses of MeV ions2002In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 186, p. 344-348Article in journal (Refereed)
    Abstract [en]

    Deep level transient spectroscopy (DLTS) is used to study the distributions as a function of depth of the single negative divacancy complex in n-type FZ silicon implanted with low doses of H, He and O ions, The energies of the incoming ions are chosen to correspond to the same projected range, i.e. about 24 mum. The defect distribution is found to be relatively broad as compared to Monte Carlo simulations of the initially created vacancy distribution, particularly for the case of proton implantation. Furthermore, it is shown that the yield of divacancies, per generated vacancy, increases slightly with incoming ion mass and is three times higher at half the projected range than in the damage peak.

  • 48.
    Hallén, Anders
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Linnarsson, Margareta K.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Ion implantation technology for silicon carbide2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 306, p. 190-193Article in journal (Refereed)
    Abstract [en]

    Ion implantation is a key process technique for semiconductor materials, in particular silicon, for local tailoring of the semiconductor properties. The wide bandgap semiconductor silicon carbide (SiC) features outstanding material properties for high power and high temperature electronic devices, but the properties of SiC also make it difficult to manufacture and process the material. The development of implantation technology for SiC has therefore necessitated several changes, from mainstream silicon implantation technology. This paper will discuss the difficulties with implantation of SiC for manufacturing of electronic devices and also describe how the problems have been overcome, for instance by implantation at elevated temperatures and using high temperature post-implant annealing. (C) 2016 Elsevier B.V. All rights reserved.

  • 49.
    Hallén, Anders
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Moschetti, Giuseppe
    RBS channeling measurement of damage annealing in InAs/AlSb HEMT structures2014In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 332, p. 172-175Article in journal (Refereed)
    Abstract [en]

    Electrical isolation of InAs/AlSb high electron mobility transistors has been achieved by the ion implantation isolation technique. The multilayered structures are grown by molecular beam epitaxy on GaAs substrates. The optimal isolation is provided by damaging patterned areas by 100 keV Ar ions implanted at room temperature using fluence of 2 x 10(15) cm(-2), and then annealing the samples in 365 degrees C for 30 min. The damage build-up and annealing is studied by channeling Rutherford backscattering spectrometry (RBS) and compared to sheet resistance measurements. Only a low level of damage annealing can be seen in RBS for the post-implant annealed samples, but for Ar fluence higher than 2 x 10(14) cm(-2), a strong electrical resistivity increase can still be achieved.

  • 50.
    Hallén, Anders
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nawaz, Muhammad
    Zaring, Carina
    Usman, Muhammad
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Domeij, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Low-Temperature Annealing of Radiation-Induced Degradation in 4H-SiC Bipolar Junction Transistors2010In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 31, no 7, p. 707-709Article in journal (Refereed)
    Abstract [en]

    Radiation hardness is tested for 4H-SiC n-p-n bipolar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 x 107 cm(-2) of 10 MeV C-12 can be clearly detected in the forward-output characteristics, I-C(V-CE). At this low dose, no influence of ion radiation is seen in the open-collector characteristics, I-B(V-EB), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420 degrees C for 30 min, a complete recovery of the electrical characteristics is accomplished.

12345 1 - 50 of 210
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