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  • 1
    Electronic Resource
    Electronic Resource
    Hexagonal voids and the formation of micropipes during SiC sublimation growth (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4625-4630 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hexagonal voids observed in sublimation grown SiC boules were examined using optical microscopy, atomic force microscopy (AFM), scanning electron microscopy, KOH etching, and synchrotron white-beam x-ray topography. Voids formed at imperfections in the attachment layer between the seed and crucible cap. They are platelet-like in shape with lateral sizes between 50 and 750 μm and thickness along the c axis between 5 and 25 μm. Growth steps were observed on the void facets closest to the seed and evaporation steps were observed on void facets closest to the growth surface, providing evidence for void movement during crystal growth. AFM images revealed that growth steps nucleate at a void sidewall, flow across the bottom of the void, and terminate in a trench-like depression. KOH etching of waters between the void and seed revealed dislocations lining up along the trace of the void path, often with higher densities corresponding to the location of the trench. X-ray topographs showed a random distribution of screw dislocations in the crystal volume above the void, and an absence of screw dislocations in the volume directly below the void. Hollow-core superscrew dislocations, called micropipes, were found at the corners of the void trace. Image forces associated with growth steps and void sidewalls are used to explain the formation of micropipes. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355716
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  • 2
    Electronic Resource
    Electronic Resource
    Micropipe Dissociation through Thick n〈sup〉+〈/sup〉 Buffer Layer Growth (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 600-603 (Sept. 2008), p. 167-170 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Thick (〉 25 µm) 4H n+ epitaxial layer growth was performed on 4H n+ substrates utilizing chlorine containing etch chemistries in a hot wall CVD system. Optimization of the n+ epitaxial layer growth was achieved by varying C/Si ratio and N2 flow. Desired epitaxial layers have doping levels 〉 5x1018 cm-3, epitaxial surface roughness 〈10 nm on a 20x20 µm area and overall micropipe density reduction. To confirm the conversion of micropipes into closed core screw dislocations, microscopic examination of the epitaxial and wafer surfaces was carried out after KOH etching. Grazing incidence x-ray topography (XRT) as well as cross sectional XRT and microscopy were also performed. The cross sectional evaluation showed that the dissociation of the micropipes occurs very close to the epitaxy/wafer interface
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/20/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.600-603.167.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Sense Determination of c-Axis Screw Dislocations in 4〈i〉H〈/i〉-SiC (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 600-603 (Sept. 2008), p. 297-300 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Grazing-incidence synchrotron topography studies of micropipes (MPs) and closed-corethreading screw dislocations (TSDs) have been carried out and the results compared with ray-tracingsimulations. Simulations indicate that both MPs and TSDs appear as roughly elliptically shaped whitefeatures which are canted to one side or the other of the g-vector depending on the dislocation senseand which have asymmetric perimeters of dark contrast which are greatly enhanced on the sidetowards which the feature is canted (again depending on the dislocation sense). For MPs,observations are generally consistent with this although the cant of the features is more obviouslydiscerned than the asymmetry in the perimeter contrast. Sense assignment for MPs has been validatedusing back-reflection reticulography. For TSDs, observation are again generally consistent with thesimulations although the smaller feature size and the variability in the line direction of the TSDs makethe asymmetry of perimeter contrast a more obvious and reliable way to determine the dislocationsense than the sense of cant. TSD dislocation senses so obtained were validated using back-reflectionimages of same-sign and opposite-sign pairs
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/20/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.600-603.297.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Non-Equilibrium Carrier Diffusion and Recombination in Semi-Insulating PVT Grown Bulk 6H-SiC Crystals (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 527-529 (Oct. 2006), p. 469-472 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We applied a non-degenerate four wave mixing (FWM) technique to investigate carriergeneration, diffusion and recombination processes in PVT-grown semi-insulating wafers of 6H-SiCat 300 K. The resistivity of samples, cut from different places of a boule as well as from differentboules, varied in range from a few [removed info]⋅cm up to 1010 [removed info]⋅cm. Interband excitation (at 355 nm) and belowbandgap excitation (at 532 nm) allowed to study dynamics of the bipolar plasma and the contributionof deep levels to carrier generation and recombination. The nonequilibrium carrier lifetime wasshorter in the samples of higher resistivity, in accordance with the increasing density of deep levels.The bipolar plasma diffusion in high-resistivity samples (~109 [removed info]⋅cm) provided the value of thediffusion coefficient D = 4.4 cm2/s and hole mobility μh = (88 ± 6) cm2/Vs
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.527-529.469.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Resistivity Distribution in Undoped 6H-SiC Boules and Wafers (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 527-529 (Oct. 2006), p. 51-54 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: For undoped 6H-SiC boules grown by physical vapor transport the variations of resistivity,of the type and density of deep electron and hole traps, and of the concentration of nitrogen and boronwere studied as a function of position in the cross section normal to the growth axis and along thegrowth direction. It was observed that the concentrations of all deep electron and hole traps decreasedwhen moving from seed to tail of the boule and from the center to the edge of the wafers. Modeling ofthe growth process suggests that the C/Si ratio increases in a similar fashion and could be responsiblefor observed changes. We also discuss the implications of such stoichiometry changes oncompensation mechanisms rendering the crystals semi-insulating and on electrical uniformity ofSI-SiC wafers
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.527-529.51.pdf
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