PVT Growth of 6H SiC Crystals and Defect Characterization
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PVT Growth of 6H SiC Crystals and Defect Characterization Govindhan Dhanaraja, Feng Liua, Michael Dudleya, Hui Zhangb and Vish Prasadc a Dept. of Materials Science and Engineering b Dept. of Mechanical Engineering State University of New York at Stony Brook Stony Brook, NY 11794 c Dept. of Mechanical Engineering, Florida International University, Miami, FL 33199 ABSTRACT SiC single crystals have been grown by seeded sublimation method using physical vapor transport (PVT) system designed and fabricated in our laboratory. A novel multi-segmented graphite insulation has been used for improved heat containment in the hot-zone. Numerical modeling was used to obtain the temperature field and predict various growth parameters. The grown crystals were characterized using AFM, SWBXT and chemical etching. INTRODUCTION Silicon carbide (SiC) is a potential semiconductor material to replace and outperform the conventionally used silicon crystal in several electronic devices for high power and high frequency and high temperature applications because of its unique combination of properties such as high electric field break down strength, high electron velocity and high thermal conductivity (1-7). The wide bandgap of SiC results in a low leakage current even at high temperature. Among the numerous SiC polytypes, 4H and 6H polytypes are the most interesting from the device point of view because they can be grown in bigger sizes. Physical vapor transport (PVT) growth, also known as seeded sublimation growth, has been the most successful method to date for growing large SiC single crystals. In this method, SiC powder in a semisealed crucible is sublimed and recrystallized on a seed crystal maintained at a slightly lower temperature. The crystal growth process of SiC is complex and difficult to optimize due to the fact that the operating temperatures are extreme (2100°C- 2500°C) and monitoring and control are difficult. Since the growth process occurs in an almost air-tight graphite crucible it is not feasible to observe the growing boule or determine experimentally the exact thermal conditions in the growth zone due to high operating temperatures and the opacity of the graphite crucible (3,7-8). The temperature field in the hot-zone is predicted using numerical modeling (9). We have grown SiC crystals using a PVT system designed and fabricated in our laboratory. The crystals have been characterized using Atomic Force Microscope (AFM), chemical etching and Synchrotron White Beam X-ray Topography (SWBXT) techniques. This was achieved as a primary part of our research program aimed at developing an understanding of the origin of micropipe nucleation during the growth of SiC crystals by PVT process.
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EPERIMENTAL DETAILS AND RESULTS PVT system and modeling The PVT SiC crystal growth system designed and fabricated in our laboratory (8) consists of an induction power-supply, a growth chamber, a hot-zone, IR pyrometers for non-contact temperature measurement, a high vacuum system with a control to monitor and maintain the A
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