Characterization of 4H-SiC Monocrystals Grown by Physical Vapor Transport

SiC is gaining importance as a wide band gap semiconductor for high temperature and high frequency devices. This technology has been rejuvenated with advent of the modified version of the Lely process, capable of producing single crystal boules of SiC. However, the presence of microstructural defects such as micropipes has limited widespread device applications; results from commercially available wafers, and from our in-house experiments reveal a continuing decrease in the micropipe density due to a better understanding of their formation processes. In this paper we review studies of factors contributing to the formation of micropipes. Both N⁺ and semi-insulating crystals of 4H-SiC with <10 micropipes cm⁻² can be produced by careful control of growth conditions. The current trend in the reduction of micropipe density bodes well for the fabrication of high power devices such as thyristors, which require large defect free areas for successful operation.