Hollow defect elimination during solution growth of SiC
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Hollow defect elimination during solution growth of SiC B.M. Epelbaum, D. Hofmann, M. Müller and A. Winnacker University of Erlangen-Nürnberg, Dept of Materials Science 6, Martensstr. 7, D-91058 Erlangen, Germany ABSTRACT Using pure and alloyed silicon melt saturated with carbon we investigated systematically hollow defect elimination during SiC solution growth over a wide temperature range from 1500°C to 2100°C. In the process of solution growth all hollow defects present in a substrate demonstrate an evident tendency to act as growth centers and after an adequate period of treatment they were overgrown. Growth morphologies observed in the vicinity of hollow defects are rather different. A new visualization method is proposed, which reveals crystalline defects associated with hollow cores and allows to detect the quantity and the distribution of HD in a whole SiC wafer. Classification of hollow defects based on these observations is presented and the corresponding closing mechanisms are discussed. INTRODUCTION Liquid phase epitaxy (LPE) has been shown to be a promising method to close hollow defects (HD) in SiC wafers prepared by the physical-vapor-transport (PVT) technique [1-3]. Hollow defects in SiC usually are referred to as screw-dislocation based micropipes (MP) [4] and they are known to be one of the critical factors limiting the successful application of this important semiconductor material. In this regard the understanding of HD origin during the PVT crystal growth process and their behavior during subsequent LPE treatment is of marked importance. In spite of numerous literature reports on micropipes in SiC crystals grown under various conditions, the nature of HD is still uncertain. In agreement with Frank prediction [4] hollow core becomes evident in screw dislocation lying along the [0001] axis with large Burgers vector b=nc, if n≥2 for 6H SiC and n≥3 for 4H SiC. The diameter of the corresponding hollow cores varies in the range 0.2-3µm for 2
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