Experimental investigation of different configurations for the seeded growth of SiC crystals via a VLS mechanism

Abstract

The growth of SiC crystals or epilayers from the liquid phase has already been reported for many years. Even if the resulting material can be of very high structural quality and the possibility to close micropipes was demonstrated, handling the liquid phase still is a challenge. Moreover, it is highly difficult to stabilize the C dissolution front and then to stabilize the growth front over a long growth time. Based on the Vapour-LiquidSolid (VLS) mechanism, we present a new configuration for the growth of SiC single crystal which should allow first to simplify the liquid handling at high temperature and second to precisely control the crystal growth front. The process consists in a modified top and bottom seeded solution growth method, in which the liquid is held under electromagnetic levitation and fed from the gas phase. 3C-SiC crystals exhibiting wellfaceted morphology were successfully obtained at 1100-1200°C with exceptional growth rates, varying from 1 to 1.5 mm/h in Ti-Si melt. It was shown that the nucleation density decreases simultaneously with increasing propane partial pressure. At 1200-1400°C, thick homoepitaxial 6H-SiC layers were successfully obtained in Co-Si and Ti-Si melts, with growth rate up to 200 µm/h. Large terraces with smooth surfaces are observed suggesting a layer by layer growth mode, and the influence of the system pressure was demonstrated. It was shown that the terrace size decrease simultaneously with increasing propane partial pressure which suggests the beginning of a two dimensional to three dimensional growth mode transition.