ENERGY-BAND STRUCTURE OF SIC POLYTYPES BY INTERFACE MATCHING OF ELECTRONIC WAVE-FUNCTIONS

We interpret SiC polytypes as natural superlattices, consisting of mut ually twisted cubic layers. A method is presented to calculate the ele ctron band structure of any polytype, based on an empirical pseudopote ntial description of cubic SiC. Bloch and evanescent waves belonging t o cubic layers are matched at interfaces in order to make up the wave functions of the respective polytypes. Band gaps of hexagonal and rhom bohedral modifications are in excellent agreement with experimental da ta such that the nearly linear relationship between the indirect gap a nd the hexagonal nature is reproduced. A simple explanation of this re lationship is given in terms of a Kronig-Penney-like model.