Transition metals in silicon carbide -SiC- - vanadium and titanium

Vanadium, substituting for silicon in SiC-polytypes, has been identified as an amphoteric deep level defect. Electron Spin Resonance (ESR) is observed for the neutral state Vhigh4plus (3dhigh1), S is equal to 1/2 and for the Ahighminus-state Vhigh3plus(3dhigh2), S is equal to 1. By photo-ESR, the position of the (0/plus) donor level is found to occur near midgap in 6H-SiC. Near-infrared, 1.3 - 1.5 Mym, photoluminescence and absorption, arising from internal 3d-shell transitions, high2Tsub2 <-> high2E, are observed for the neutral state Vhigh4plus (3dhigh1) . These sharp-line spectra were found to be very specific for a given SiC-polytype. Isoelectronic, electrically inactive, titanium impurities have been found, by ESR, to complex preferentially with shallow nitrogen donors. The resulting TisubSi-Nsubc pair then acts as deep donor, Esubc - 0.6 eV, in 6H-SiC. The isolated titanium defect forms a deep acceptor state in 4H-SiC, but not in the 6Hpolytype.