ELECTRONIC-STRUCTURE OF THE SHALLOW BORON ACCEPTOR IN 6H-SIC - A PULSED EPR ENDOR STUDY AT 95 GHZ/

A high-frequency pulsed electron paramagnetic resonance electron-nucle ar double-resonance (ENDOR) study on a C-13-enriched 6H-SiC single cry stal is reported. This type of spectroscopy, owing to its superior spe ctral resolution, allows us to obtain detailed information about the e lectronic structure of the shallow boron acceptor centers in 6H-SiC. I t is concluded that around 40% of the spin density is localized in the p(z) orbital of a carbon which is nearest to boron. The p(z) orbital is directed along the C-B connection line and is parallel to the c axi s for the hexagonal site and 70 degrees away from the c axis for the t wo quasicubic sites. We conclude that the C-B bond is a dangling bond, that boron is neutral, and that there is no direct spin density on bo ron. There is a relaxation of the carbon atom, carrying the spin densi ty, and the boron atom away from each other. From a Si-29 and C-13 END OR study it is further concluded that around 60% of the spin density i s distributed in the crystal with a Bohr radius of 2.2 Angstrom.