Inequivalent Sites and Multiple Donor and Acceptor Levels in SiC Polytypes

Abstract

There is now experimental evidence of three nitrogen donor levels in $6H$ SiC. The possibility of such multiple levels is a result of crystallographically inequivalent sites in the large unit cells of the common SiC polytypes. The existence of multiple levels indicates departures from the hydrogenic approximation. For x-ray scattering, the usual structure factor approximation, in which polytypes are considered as various stacking orders of equivalent planes, may be inadequate.