Nucleation of 3C–SiC on 6H–SiC from a liquid phase Maher Soueidan a,b, * , Gabriel Ferro a , Olivier Kim-Hak a , Florence Robaut c , Olivier Dezellus a , Jacques Dazord a , Franc ¸ois Cauwet a , Jean-Claude Viala a , Bilal Nsouli b a Laboratoire des Multimateriaux et Interfaces, UMR-CNRS 5615, Universite ´ Claude Bernard Lyon 1, 43 Bd du 11 nov. 1918, 69622 Villeurbanne, France b Lebanese Atomic Energy Commission – CNRS, P.O. Box 11-8281, Riad El Solh 1107 2260 Beirut, Lebanon c Consortium des Moyens Technologiques Communs, INPG, 120 rue de la piscine, 38502 St Martin d’He `res, France Received 11 June 2007; received in revised form 28 August 2007; accepted 29 August 2007 Available online 18 October 2007 Abstract The aim of this work is to elucidate the mechanism involved in the 3C–SiC formation during growth by a vapor–liquid–solid mech- anism on 6H–SiC substrate. Polytype selection is shown to occur at the first stage of the experiments, before propane injection into the reactor. The contact of the seed with a Si–Ge melt during the initial heating ramp causes the formation of 3C–SiC islands on the seed surface, probably below 1200 °C. The proposed mechanism first involves a partial dissolution of the seed in a Ge-rich liquid which becomes C-supersaturated. Then the Si content of the liquid rapidly increases, which provokes the precipitation of the dissolved carbon in the form of 3C–SiC islands. When growth starts upon propane injection, these islands enlarge and coalesce to form a continuous 3C– SiC layer. If the growth temperature is too high (P1550 °C), the initial 3C–SiC islands are dissolved and homoepitaxial layers are obtained. Ó 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Thin films; Atomic force microscopy (AFM); Electron backscattering diffraction (EBSD); Carbides; Semiconductor 1. Introduction Silicon carbide is a strategic wide-bandgap semiconduc- tor with high thermal conductivity, excellent thermal stabil- ity, high breakdown field and high electron saturation velocity, which makes it a good candidate for high temper- ature, high power, high frequency and radiation-resistant applications [1]. There are many possible crystallographic structures (polytypes) for SiC. The difference between each polytype comes only from the periodicity of the stacking sequence of tetrahedrally bonded Si–C bilayers [2]. 3C– SiC is the only SiC polytype with a cubic crystal (diamond like) structure, and thus presents additional interest com- pared with the other SiC polytypes, which should cause it to be considered increasingly in the forthcoming years. For instance, its reduced density of near-interface traps may help increase drift mobility [3,4], and its lower band- gap would be more appropriate for inversion channel MOS applications [5]. 3C–SiC layers are usually grown on Si substrate using chemical vapor deposition (CVD). Major problems are, however, encountered in this heteroepitaxial system, such as the large lattice mismatch of 20% and the difference in thermal expansion coefficients between SiC and Si. Notice- able improvement in crystalline quality was obtained by Nagasawa et al. using undulant Si substrate and high growth rates [6]. Further improvement was demonstrated later with the switch-back epitaxy process but the wafer bending, due to expansion mismatch, is not solved on this improved material [7]. 1359-6454/$30.00 Ó 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actamat.2007.08.046 * Corresponding author. Address: Laboratoire des Multimateriaux et Interfaces, UMR-CNRS 5615, Universite ´ Claude Bernard Lyon 1, 43 Bd du 11 nov. 1918, 69622 Villeurbanne, France. Tel.: +33 4 72 43 82 31; fax: +33 4 72 44 06 18. E-mail address: maher.soueidan@univ-lyon1.fr (M. Soueidan). www.elsevier.com/locate/actamat Available online at www.sciencedirect.com Acta Materialia 55 (2007) 6873–6880