Abstract

Scanning electron micrographs have been obtained from the edges of Lely vapour grown single crystals of silicon carbide, parallel to the (0001) direction. These edges contain a superposition of various polytypes in syntactic coalescence with each other and adjoining regions of one-dimensional disorder (1DD). The exact location of the common low period 6H, 15R & 4H polytypes along the c-axis has been established with the technique of SRS XRDT [1]. Synchrotron X-ray topography has the ability not only to map dislocation density but also resolve detail that enables models of the polytype content along the edges to be built up. A unique database on the spatial distribution of polytypes has thus been compiled.

A comparative study has been made of the location of the features observed using white radiation SRS XRDT and the regions of Cathodoluminescence (CL) observed from the same hexagonal edges [2]. The coincidence of defect bands and one-dimensionally disordered (1DD) layers with the regions exhibiting CL is examined. The widespread interest in SiC as a high temperature, power semiconductor device can be attributed to its wide band gap electronic properties. Further SiC can display a mosaic spatial distribution of polytypes each of known location, which has the potential for optical emission.

References

[1] Kelly J.F., Barnes P., Fisher G.R., Radiat. Phys. Chem., 45, 509-522 (1995).

[2] Saparin G.V., Obyden S.K., Mokhov E.N., Roenkov A.D., Ahmedov B.A., Scanning, 16, 21-25 (1994).