Neutral aluminum and gallium four particle complexes in silicon carbide polytypes

Optical studies provide a great amount of information about acceptors in SiC. The optical recombination of neutral acceptor four particle (bound exciton) complexes has been observed in 4H, 6H, 15R and 3C SiC for Al; 4H, 6H and 3C SiC for Ga; and in 4H SiC for the shallow B acceptor. A model for the electronic structure of neutral acceptor four particle complexes based on symmetry provides a description of the no-phonon spectra for Al and Ga, when the possibility of lattice strain is included. This model is consistent with the numbers of no-phonon lines observed for Al and Ga in 3C, 4H and 6H SiC, but there are too many no-phonon lines for Al in 15R SiC. The model is further developed and applied to Zeeman spectra of Al and Ga four particle complexes in 6H SiC, providing further insight into their electronic structure.