Papers by Keyword: Si-Face

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Authors: Yuichi Nagahisa, Yoshisige Tsuchiya, Eisuke Tokumitsu
Abstract: Effects of residual oxygen in an annealing chamber on graphitization of SiC along with surface pre-treatment process have been investigated. As a pre-treatment process, SiO2 was formed on 4H-SiC(0001) substrates by thermal oxidation before graphene formation annealing. Epitaxial graphenes were formed in several O2 pressures and effects on graphitization of SiC were evaluated. It is shown that quality of graphene on SiC substrates which formed without pre-oxidation degraded by the presence of residual O2 in the chamber. It is demonstrated that SiO2 pre-oxidation films (about 10nm) were effective to prevent such degradations, for all O2 pressures that we examined in this work. In addition, at O2 pressure of 1.1x10-1Pa, with SiO2 pre-oxidation, a graphene growth rate was increased, which indicates that a certain level of O2 pressure enhances graphene growth.
Authors: Hidenori Koketsu, Tomoaki Hatayama, Hiroshi Yano, Takashi Fuyuki
Abstract: The sub-trenches in 4H-SiC Si- and C-faces could be disappeared by the thermal treatment in chlorine ambience at 900-1000oC. The surface morphologies of the thermally treated trench-sidewalls were unchanged. It is considered that the sub-trench is selectively removed because thermally Cl2 etching rate of the (0001) Si- and (000-1) C-face are different to the (11-20) and (1-100).
Authors: Takashi Aigo, Wataru Itoh, Tatsuo Fujimoto, Takayuki Yano
Abstract: In this paper, we present a comparison of defects in 4H-SiC epilayers grown on 4o off-axis (0001) and (000-1) substrates. It was confirmed using high sensitive surface observation and micro-Raman spectroscopy that the generation of epitaxial defects on (000-1) C-face substrates was less susceptible to substrate morphological defects such as pits than that on (0001) Si-face substrates and 'comet-like' defects on (000-1) C-faces were caused by the inclusion of 3C-SiC. Moreover, PL imaging observation showed that stacking fault densities decreased when increasing the growth temperature, and they increased when increasing the C/Si ratio, irrespective of the face polarity. The densities, however, were lower for C-faces at higher growth temperature and C/Si ratio. The present results indicated that C-faces were preferable to Si-faces to achieve smooth step-flow growth suppressing epitaxial defects and stacking faults, which were influenced by the substrate morphological defects and the fluctuation of C/Si ratio in the epitaxial growth.
Authors: Tetsuo Hatakeyama, Kyoichi Ichinoseki, Hiroshi Yamaguchi, N. Sugiyama, Hirofumi Matsuhata
Abstract: The origins of certain types of micrometer-scale surface morphological defects on SiC epitaxial layers are clarified using X-ray topography. Two types of surface morphological defects are commonly observed on Si- and C-face epitaxial layers. Relatively large pits (around 4μm×2μm) originate from threading screw dislocations (TSDs). Relatively small pits (around 1.5μm×1μm) originate from threading edge dislocations (TEDs). The shapes and depths of these surface morphological pits depend on the fabrication history of the epitaxial wafers.
Authors: Markus Ostler, Roland J. Koch, Florian Speck, Felix Fromm, Hendrik Vita, Martin Hundhausen, Karsten Horn, Thomas Seyller
Abstract: Epitaxial graphene (EG) grown on SiC(0001) resides on the so-called buffer layer. This carbon rich (6√3×6√3)R30° reconstruction is covalently bound to the topmost silicon atoms of the SiC. Decoupling the graphene buffer layer from the SiC interface is a well studied topic since successful intercalation has been shown for hydrogen [1-3]. Recently, intercalation was also shown for oxygen [4, 5]. We present ARPES, XPS and Raman spectroscopy studies to determine the quality of oxygen intercalated buffer layer samples in terms of decoupling and integrity of the transformed graphene layer. The decoupling effect is demonstrated by ARPES measurements showing a graphene-like π band. XPS shows whether the oxidation takes place in the buffer layer or at the interface. Raman spectroscopy is well suited to investigate oxygen induced defects in graphene-like material.
Authors: Frank Schmid, Michael Laube, Gerhard Pensl, Günter Wagner, Manfred Maier
Authors: Michael Grieb, Masato Noborio, Dethard Peters, Anton J. Bauer, Peter Friedrichs, Tsunenobu Kimoto, Heiner Ryssel
Abstract: In this work, the electrical characteristics and the reliability of 80nm thick deposited oxides annealed in NO and N2O on the 4H-SiC Si-face for gate oxide application in MOS devices is analyzed by C-V, I-V measurements and by constant current stress. Compared to thermally grown oxides, the deposited oxides annealed in N2O or NO showed improved electrical properties. Dit-values lower than 1011cm-2eV-1 have been achieved for the NO sample. The intrinsic QBD-values of deposited and annealed oxides are one order of magnitudes higher than the highest values reported for thermally grown oxides. Also MOSFETS were fabricated with a channel mobility of 20.05 cm2/Vs for the NO annealed deposited oxide. Furthermore annealing in NO is preferred to annealing in N2O regarding µFE- and QBD-values.
Authors: Hiroki Miyake, Tsunenobu Kimoto, Jun Suda
Abstract: We demonstrate 4H-SiC bipolar junction transistors (BJTs) with an enhanced current gain over 250. High current gain was achieved by utilizing optimized device geometry as well as optimized surface passivation, continuous epitaxial growth of the emitter-base junction, combined with an intentional deep-level-reduction process based on thermal oxidation to improve the lifetime in p-SiC base. We achieved a maximum current gain (β) of 257 at room temperature and 127 at 250°C for 4H-SiC BJTs fabricated on the (0001)Si-face. The gain of 257 is twice as large as the previous record gain. We also demonstrate BJTs on the (000-1)C-face that showed the highest β of 439 among the SiC BJTs ever reported.
Authors: Brenda L. VanMil, Rachael L. Myers-Ward, Joseph L. Tedesco, Charles R. Eddy, Glenn G. Jernigan, James C. Culbertson, Paul M. Campbell, J.M. McCrate, S.A. Kitt, D. Kurt Gaskill
Abstract: Graphene layers were created on both C and Si faces of semi-insulating, on-axis, 4H- and 6H-SiC substrates. The process was performed under high vacuum (<10-4 mbar) in a commercial chemical vapor deposition SiC reactor. A method for H2 etching the on-axis substrates was developed to produce surface steps with heights of 0.5 nm on the Si-face and 1.0 to 1.5 nm on the C-face for each polytype. A process was developed to form graphene on the substrates immediately after H2 etching and Raman spectroscopy of these samples confirmed the formation of graphene. The morphology of the graphene is described. For both faces, the underlying substrate morphology was significantly modified during graphene formation; surface steps were up to 15 nm high and the uni-form step morphology was sometimes lost. Mobilities and sheet carrier concentrations derived from Hall Effect measurements on large area (16 mm square) and small area (2 and 10 m square) samples are presented and shown to compare favorably to recent reports.
Authors: Stefano Leone, Henrik Pedersen, Anne Henry, Olof Kordina, Erik Janzén
Abstract: The homoepitaxial chloride-based CVD growth is demonstrated on Si-face on-axis 4H-SiC substrates. The use of chloride-based CVD has allowed growth of 100% 4H-SiC epitaxial layers with a growth rate of 20µm/h, thus about seven times higher than with standard precursors. It was also found that chlorine etches preferentially the 3C-SiC inclusions that tends to nucleate on Si-face on-axis substrates. Therefore the Cl/Si ratio is a fundamental process parameter to optimize.
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