Thermal and doping dependence of 4H-SiC polytype transformation

We have observed characteristic temperatures, anneal times, and doping densities that lead to stacking faults and 3C-SiC-like bands in 4H-SiC epilayers. Low energy cathodoluminescence spectroscopy measurements reveal a temperature threshold of 800 degreesC for emergence of these features in thermally oxidized or argon annealed 4H-SiC with an activation energy approximate to2.5 eV. Stacking fault generation and polytype transformation exhibits a strong doping dependence, appearing only in a range of highly doped n-type 4H-SiC. Systematics of these strain and/or electronic effects induced by high N concentrations can be used to control structural instabilities during SiC device fabrication. (C) 2002 American Institute of Physics.