The microscopic and electronic structure of shallow donors in SiC

Nitrogen donors in 6H-, 4H- and 3C-SiC were investigated using conventional electron paramagnetic resonance (EPR) and electron nuclear double resonanc e (ENDOR) and the experimental results are discussed. An attempt is present ed to interpret the experimentally found large differences in hyperfine int eractions of the N-14 nuclei on the various inequivalent sites in the diffe rent polytypes of SiC in terms of valley-orbit splitting and "central-cell corrections" in the framework of the effective mass theory (EMT). Phosphoru s doping by neutron transmutation in 6H-SiC resulted in various phosphorus- related EPR spectra previously associated with shallow phosphorous donors a nd phosphorus-vacancy complexes. In analogy to the new interpretation of th e nitrogen donor spectra in various polytypes, it is proposed that all phos phorus-related spectra found hitherto in 6H-SiC are due to isolated phospho rus donors in ground and excited EMT states.