Silicon Carbide and Related Materials 2004

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Authors: Andreas Fissel
Abstract: The different aspects of molecular beam epitaxy (MBE) for producing two-dimensional (Quantum well), one-dimensional (Quantum wire and rod), and zero-dimensional (Quantum dot) structures based on SiC for functional applications are discussed. Development and implementation of a suitable MBE growth procedure for fabrication of heteropolytypic layer sequences are demonstrated in context with thermodynamic considerations. Furthermore, the growth of onedimensional structures based on cubic wires and nanorod arrays, also grown on Si(111), is shown. Moreover, the perspectives of quantum dot structures and a novel way to form 3C-SiC-dot structures within α-SiC has been discussed.
163
Authors: K.L. Safonov, Yuri V. Trushin, Oliver Ambacher, Jörg Pezoldt
Abstract: Solid source molecular beam epitaxy was applied to create silicon carbide nanoclusters on silicon. The island size distribution can be controlled by an appropriate substrate temperature, carbon fluxes and process times. Rate equation computer simulation was applied to simulate the experimental obtained nano scale nuclei properties.
169
Authors: Petia Weih, Henry Romanus, Thomas Stauden, Lothar Spieß, Oliver Ambacher, Jörg Pezoldt
Abstract: In the present work cubic 3C-(Si1-xC1-y)Gex+y solid solutions were grown at different^temperatures by molecular beam epitaxy on on-axis 4H-SiC (0001) substrates. Two different growth methods are compared in order to explore the optimal growth conditions for the incorporation of Ge into the SiC lattice during the low temperature epitaxy. For this reason simultaneous growth and migration enhanced epitaxy were used. The chemical composition of the grown layers were analyzed by energy dispersive x-ray methods during transmission electron microscopy investigations. It was found that the migration enhanced epitaxy is a more suitable technique for the formation of high quality (Si1-xC1-y)Gex+y solid solutions. Additionally, polytypes transition from 4H-SiC to 3C-SiC occurs during the growth independent of the applied growth technique.
173
Authors: S. Sugishita, A. Shoji, Yoshihiko Mukai, Taro Nishiguchi, K. Michikami, Toshiyuki Isshiki, Satoru Ohshima, Shigehiro Nishino
Abstract: Lateral epitaxial overgrowth (LEO) is known as method of defects reduction for GaN. LEO is expected to reduce crystal defects on hetero-epitaxial growth of 3C-SiC. (100) Si substrate patterned with SiO2 mask was used as the substrate. Before CVD process, V shape crater was made on Si surface by HCl etching. And growth condition of CVD was optimized. Single crystal of 3C-SiC was grown laterally on SiO2 layer. Cross-sectional transmission electron microscopic observation indicated that crystal quality of LEO region was single and no defect crystal.
177
Authors: Mitsutaka Nakamura, Toshiyuki Isshiki, Taro Nishiguchi, Koji Nishio, Satoru Ohshima, Shigehiro Nishino
Abstract: Hetero-epitaxial CVD growth of 3C-SiC on a Si(110) substrate gives a (111) crystal with low defects density. However, double positioning growth often disturbs growth of a single crystal. The growth on an off-axis Si(110) substrate suppressed propagation of the double positioning defects in the grown layer effectively. Cross-sectional transmission electron microscopy revealed the details of the suppression process on the off-axis substrate. The suppression mechanism and the origin of the defects formation at double positioning boundaries were interpreted by the growth model based on an anisotropic growth rate on (111) plane of 3C-SiC.
181
Authors: Toshiyuki Isshiki, Mitsutaka Nakamura, Taro Nishiguchi, Koji Nishio, Satoru Ohshima, Shigehiro Nishino
Abstract: Interfaces between a Si(110) substrate and 3C-SiC crystals grown hetero-epitaxially by CVD were investigated by cross-sectional transmission electron microscopy. Gas flow condition during the carbonization process affects the roughness of the substrate surface and there is an optimum condition to preserve the flat surface. High quality 3C-SiC crystals grew only on the flat substrate, with crystallographic relationship of Si[1-10]//SiC[1-10] and Si[001]//SiC[1-1 - 2], because the well-lattice-match relationship was limited in a two-dimensional region at the SiC(111)/Si(110) interface. Using the optimum condition, some kinds of roughness at an atomic scale remained on the surface of the substrate. Nanoscopic observation of the crystals grown on an off-axis substrate revealed the influence of the roughness on the epitaxial growth and the defects generation at the interface.
185
Authors: David Méndez, A. Aouni, Daniel Araújo, Gabriel Ferro, Yves Monteil, Etienne Bustarret
Abstract: One of the problems with Si(001)/3C-SiC templates is that they involve highly defective interfaces due to the presence of misfit dislocations, voids and planar defects that degrade the SiC layer quality. A way to accommodate the high lattice mismatch between these materials and reduce the voids density is to carbonize the Si substrate before the epitaxial growth. In this contribution an alternative way to reduce planar defects density is presented by analyzing the relationship between planar defects and voids. Planar view and cross section transmission electron microscopy micrographs show a diminution of planar defects in the regions surrounding the voids. Due to the lower elastic energy over the voids and/or to a lateral growth in these regions, the generation of planar defects is partially deactivated, improving locally the crystalline quality of the SiC layer. The introduction of such cavities can be thus seen as a new parameter of Si/SiC templates design.
189
Authors: Taro Nishiguchi, Mitsutaka Nakamura, Koji Nishio, Toshiyuki Isshiki, Satoru Ohshima, Shigehiro Nishino
Abstract: Chemical vapor deposition of (111) 3C-SiC on (110) Si substrate was carried out, and the effect of the substrate off-axis introduced on (110) Si substrate for suppressing the twin formation in 3C-SiC hetero-epitaxial layers was investigated. From the growth on hemispherically polished (110) Si substrate, it was found that the off-axis toward the [001] Si axis had a noble effect for suppressing the twin formation, while the off-axis toward the [110] Si axis was ineffective. The growth of single 3C-SiC crystal containing few double positioning boundaries, which are related with the twin formation, was demonstrated on the (110) Si substrate 3° off-axis toward the [001] Si axis. Transmission electron microscopic observation revealed that double positioning boundaries on the (110) Si substrate off-axis toward the [001] Si axis were nearly eliminated within the initial a few hundreds nano meter in thickness.
193
Authors: Hugues Mank, Catherine Moisson, Daniel Turover, Mark E. Twigg, Stephen E. Saddow
Abstract: In this work, we have investigated the 3C-SiC re-growth on planarized 3C-SiC epitaxial layers, grown on (001)Si, after the application of a chemical mechanical polishing (CMP) process. A specific polishing process was developed for 3C-SiC to achieve a flat, high-quality surface. The interface between the deposited 3C-SiC and the polished 3C-SiC on Si film was studied by TEM characterization to determine if defects appear at this interface. It was observed that no additional defects were nucleated at the interface. The resulting re-grown film roughness, as a function of film thickness, was studied and is reported along with recommendations for future work.
197
Authors: Christian Förster, Volker Cimalla, Oliver Ambacher, Jörg Pezoldt
Abstract: In the present work an UHVCVD method was developed which allows the epitaxial growth of 3C-SiC on Si substrates at temperatures below 1000°C. The developed method enable the growth of low stress or nearly stress free single crystalline 3C-SiC layers on Si. The influence of hydrogen on the growth process are be discussed. The structural properties of the 3C-SiC(100) layers were studied with reflection high-energy diffraction, atomic force microscopy, X-ray diffraction and the layer thickness were measured by reflectometry as well as visible ellipsometry. The tensile strain reduction at optimized growth temperature, Si/C ratio in the gas phase and deposition rate are demonstrated by the observation of freestanding SiC cantilevers.
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