Electron nuclear interactions and electronic structure of spin 3/2 color centers in silicon carbide: A high-field pulse EPR and ENDOR study

High-frequency pulse electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) were used to clarify the electronic structure of the color centers with an optically induced high-temperature spin-3/2 alignment in hexagonal 4H-, 6H- and rhombic 15R- silicon carbide (SiC) polytypes. The identification is based on resolved ligand hyperfine interactions with carbon and silicon nearest, next nearest and the more distant neighbors and on the determination of the spin state. The ground state and the excited state were demonstrated to have spin S = 3/2. The microscopic model suggested from the EPR and ENDOR results is as follows: a paramagnetic negatively charged silicon vacancy that is noncovalently bonded to a non-paramagnetic neutral carbon vacancy, located on the adjacent site along the SiC symmetry c-axis.