Interaction of micropipes with foreign polytype inclusions in SiC

Synchrotron phase sensitive radiography, optical and scanning electron microscopies, and color photoluminescence have been used to study the interaction of micropipes with foreign polytype inclusions in 4H-SiC bulk crystals grown on 6H-SiC substrates. This combination of techniques confirms that micropipes agglomerate at the polytype inclusions and merge into pores. A mechanism for this phenomenon is suggested based on a three-dimensional theoretical model; the inclusion boundaries elastically interact with micropipes, causing them to migrate from the bulk to their equilibrium positions at the polytype boundaries. The turning of micropipes towards the inclusions is experimentally demonstrated, and the reduction of their density in nearby regions is revealed. Supported by experimental observations, our model helps to understand the pore formation and expansion in SiC bulk crystals. (c) 2006 American Institute of Physics.