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  • 201.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Employing discontinuous and continuous growth modes for preparation of AlN nanostructures on SiC substrates2007In: ECSCRM 2006, Newcastle, UK: Materials Science Forum Vols. 556-557, Trans Tech Publications, Switzerland , 2007, Vol. 556-557, p. 1031-1034Conference paper (Refereed)
    Abstract [en]

    In this report we present results on growth and characterization of AlN wires and thinfilms on SiC substrates. We have employed PVT technique in close space geometry for AlNdeposition on SiC off oriented substrates, most of which were prepared to have scratch-free smoothas-grown surface by SiC sublimation epitaxy. By manipulating the surface kinetics we have beenable to determine growth conditions yielding discontinuous or continuous morphologiescorresponding to nanowires and thin films, respectively. A particular feature of the latterexperiments is the fast temperature ramp up at the growth initiation. The AlN surface morphologywas characterized by optical, AFM and XRD tools, which showed good crystal quality independentof the growth mode.

  • 202.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Aligned AlN nanowires and microrods by self-patterning2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 12, p. 123103-Article in journal (Refereed)
    Abstract [en]

    Self-patterned AlN microrods and nanowires were grown on 4H-SiC substrate by a physical vapor transport method. AlN hexagonal pyramids were found to be nucleation sites for the evolution of the observed morphological forms. The average diameter and length of the nanowires are about 200  nm and 90  µm, respectively. The density of microrods corresponds to the concentration of the pyramids, while the nanowires are less compact. Low-temperature cathodoluminescence spectra of microrods show band gap emission of AlN at 208  nm, which confirms that they are AlN single crystals. A formation mechanism of the AlN structures is suggested.

  • 203.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Formation of needle-like and columnar structures of AlN2007In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 300, no 1, p. 130-135 Article in journal (Refereed)
    Abstract [en]

    The present study focused on understanding the formation of needle-like and columnar structures by investigating the initial nucleation of aluminium nitride (AlN) on SiC substrates with SEM, AFM, and XRD. The grown AlN consisted of high concentration (8×104 cm−2) hexagonal hillocks (HHs) that originate from threading dislocations in the substrate. The KOH etching technique has been used to examine the origin and formation process of HHs and defect reduction in the grown AlN crystals. A model is introduced to explain the AlN HH formation. The SEM result shows that the AlN columnar structure was formed by merging of needles, which are grown exactly on completed AlN HHs, followed by a lateral growth.

  • 204.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Growth and morphology of AlN crystals2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T126, p. 127-130Article in journal (Refereed)
    Abstract [en]

    This study focused on growth dependencies, morphological forms and initial nucleation of aluminium nitride (AlN) crystals. Epitaxial layers of AlN have been grown on 4H-SiC substrates by sublimation recondensation in a radio frequency (RF) heated graphite furnace. Both AlN nuclei size and growth rate increased as temperature was increased and decreased as the pressure was increased. The results of these effects are different kinds of surface morphology. We have observed three modes of AlN single crystals: plate-like, columnar and needle-like. Optical microscopy and scanning electron microscopy (SEM) along with atomic force microscopy (AFM) were used to characterize the crystal surface morphology. Cathodoluminescence (CL) and x-ray diffraction (XRD) were applied to determine crystal quality and crystallographic orientation of the grown crystals.

  • 205.
    Yazdi, Gholamreza
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Novel approach to AlN growth for power device applications2007In: WASMPE 2007,2007, 2007, p. 29-30Conference paper (Other academic)
  • 206.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, Alexei
    Lund University, Sweden .
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Growth of large area monolayer graphene on 3C-SiC and a comparison with other SiC polytypes2013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 57, p. 477-484Article in journal (Refereed)
    Abstract [en]

    Epitaxial graphene growth was performed on the Si-terminated face of 4H-, 6H-, and 3C-SiC substrates by silicon sublimation from SiC in argon atmosphere at a temperature of 2000 degrees C. Graphene surface morphology, thickness and band structure have been assessed by using atomic force microscopy, low-energy electron microscopy, and angle-resolved photoemission spectroscopy, respectively. Differences in the morphology of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. The uniformity of silicon sublimation is a decisive factor for obtaining large area homogenous graphene. It is also shown that a lower substrate surface roughness results in more uniform step bunching with a lower distribution of step heights and consequently better quality of the grown graphene. Large homogeneous areas of graphene monolayers (over 50 x 50 mu m(2)) have been grown on 3C-SiC (1 1 1) substrates. The comparison with the other polytypes suggests a similarity in the surface behaviour of 3C- and 6H-SiC.

  • 207.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Fabrication of free-standing AlN crystals by controlled microrod growth2008In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 300, no 5, p. 935-939 Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to propose a growth procedure for preparation of crack-free thick aluminum nitride (AlN) layers that can be easily separated from the substrate. The overall process is based on the physical vapor transport method employing a seed and a source material. In this case, the substrate is an epitaxial 4H-SiC layer and the growth of AlN is initiated at etch pits formed during the ramp up time prior to establishing growth temperature. Development of hexagonal pyramids on which arrays of microrods are formed is the core of the growth procedure. Free-standing wafers having 10 mm diameter and about 120 μm thick have been fabricated.

  • 208.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vassilevski, K.
    Newcastle University.
    Cordoba Gallego, Jose Manuel
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Gogova, Daniela
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Nikitina, I. P.
    Newcastle University.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Wright, N.G.
    Newcastle University.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Free standing AIN single crystal grown on pre-patterned and in situ patterned 4H-SiC substrates2010In: Materials Science Forum, Vols. 645-648, Transtec Publications; 1999 , 2010, Vol. 645-648, p. 1187-1190Conference paper (Refereed)
    Abstract [en]

    Free standing AIN wafers were grown on pre-patterned and in situ patterned 4H-SiC substrates by a physical vapor transport method. It is based on the coalescence of AIN microrods, which evolve from the apex of SiC pyramids grown on the SIC substrate during a temperature ramp up for in situ patterned substrate and SiC pyramids formed by reactive ion etching (RIE). This process yields stress-free (according XRD and Raman results) AIN single crystals with a thickness up to 400 mu m and low dislocation density.

  • 209.
    Zhu, Xiaolong
    et al.
    Technical University of Denmark, Lyngby.
    Ou, Yiyu
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hansen, Ole
    Technical University of Denmark, Lyngby.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Mortensen, N. Asger
    Technical University of Denmark, Lyngby.
    Xiao, Sanshui
    Technical University of Denmark, Lyngby.
    Broadband light-extraction enhanced by arrays of whispering gallery resonators2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 24Article in journal (Refereed)
    Abstract [en]

    We demonstrate a light-extraction approach using a whispering gallery resonators array. The wavelength-scale resonant dielectric nanospheres support whispering gallery modes, which can be coupled with the confined waveguide modes inside the bulk material, thus dramatically improving light extraction. Broadband light-extraction enhancement across the entire visible spectral range is achieved by exciting three low-order and low-quality-factor resonances. As an example, the broadband extraction enhancement of about 50% is obtained for the emission of fluorescent SiC at all the tested angles. The experimental results are supported by numerical simulations. Our light-extraction strategy could enable the manufacturing of high-throughput, nondestructive, and affordable optical coating in a variety of optical devices.

  • 210. Ziane, D
    et al.
    Bluet, JM
    Guillot, G
    Godignon, P
    Monserrat, J
    Ciechonski, Rafal
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, L
    Mawby, P
    Characterizations of SiC/SiO2 interface quality toward high power MOSFETs realization2004In: Materials Science Forum, Vols. 457-460, 2004, Vol. 457-460, p. 1281-1286Conference paper (Refereed)
    Abstract [en]

    The low channel mobility in N-MOS 4H-SiC transistor is a major key issue for the development of power devices with satisfactory on state characteristics. Previous works have demonstrated that this low channel mobility is due to high interface state density (Dit) near the conduction band edge. Furthermore, the realization of SiC MOSFETs sustaining high reverse field necessitates thick epitaxial layer growth. An important thickness (> 30 gm) unfortunately involves important surface roughness which may result in a high interface trap density (Dit) and surface potential fluctuation (sigma(s)) at the SiC/SiO2 interface. In this study, we focus on SiO2/SiC MOS interface quality characterization as a function of process conditions and material properties (dopant type, thick layer growth technique). Investigations of the oxide quality on thick layers grown by CVD and PVT has been realized using CV under UV lightening and GV techniques. We evidenced that the Dit value (between 10(10) cm(-2).eV(-1) and 9x10(10) cm(-2).eV(-1) from 0.9 Ev to 0.2 eV below Ec) and sigma(s) value (60 mV) were slightly lower for thick PVT layers. A discrepancy in the Dit values obtained from C-V and G-V measurements is attributed to the large surface potential standard deviation. Results from an original oxide growth process using a deposited sacrificial silicon layer under UHV conditions are also presented.

  • 211.
    Zoulis, G.
    et al.
    CNRS, Montpellier, France.
    Sun, Jianwu
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lorenzzi, J.
    Laboratoire des Multimateriaux et Interfaces, University Claude Bernard Lyon 1, Villeurbanne, France.
    Peyre, H.
    Université Montpellier 2, France.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ferro, G.
    Laboratoire des Multimateriaux et Interfaces, University Claude Bernard Lyon 1, Villeurbanne, France.
    Juillaguet, S.
    Université Montpellier 2, France.
    Yakimova, Rositza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Camassel, J.
    CNRS, Montpellier, France .
    Seeding layer influence on the low temperature photoluminescence intensity of 3C-SiC grown on 6H-SiC by sublimation epitaxy2012In: HETEROSIC and WASMPE 2011 / [ed] Daniel Alquier, Trans Tech Publications Inc., 2012, Vol. 711, p. 149-153Conference paper (Refereed)
    Abstract [en]

    We report on n-type 3C-SiC samples grown by sublimation epitaxy. We focus on the low temperature photoluminescence intensity and show that the presence of a first conversion layer, grown at low temperature, is not only beneficial to improve the homogeneity of the polytype conversion but, also, to the LTPL signal intensity. From the use of a simple model, we show that this comes from a reduced density of non-radiative recombination centers.

  • 212.
    Zoulis, Georgios
    et al.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Sun, Jian Wu
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Beshkova, Milena
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Juillaguet, S.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Peyre, H.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Camassel, J.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Investigation of Low Doped n-Type and p-Type 3C-SiC Layers Grown on 6H-SiC Substrates by Sublimation Epitaxy2010In: Silicon Carbide and Related Materials 2009, 2010, Vol. 645, p. 179-182Conference paper (Refereed)
    Abstract [en]

    Both, n-type and p-type 3C-SiC samples grown on 6H-SiC substrates by sublimation epitaxy have been investigated. From low temperature photoluminescence studies, we demonstrate a low level of residual (n and/or p-type) doping with weak compensation, which is confirmed by secondary ion mass spectroscopy in the case of p-type samples.

2345 201 - 212 of 212
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