ELECTRON-PARAMAGNETIC-RESONANCE OF SCANDIUM IN SILICON-CARBIDE

The EPR spectra of scandium accepters and Sc2+(3d) ions are observed i n 6H-SiC crystals containing a scandium impurity. The EPR spectra of s candium accepters are characterized by comparatively small hyperfine i nteraction constants, whose values are consistent with the constants f or other group III elements in SiC: boron, aluminum, and gallium accep ters. The EPR spectra of scandium accepters undergo major changes in t he temperature interval 20-30 K. In the low-temperature phase the EPR spectra are characterized by orthorhombic symmetry, whereas the high-t emperature phase has higher axial symmetry. The EPR spectra observed a t temperatures above 35 K and ascribed by the authors to Sc2+(3d) ions , or to the A(2-) state of scandium, have significantly larger hyperfi ne structure constants and narrower lines in comparison with the EPR s pectra of scandium accepters. The parameters of these EPR spectra are close to those of Sc2+(3d) in ionic crystals and ZnS, whereas the para meters of the EPR spectra of scandium accepters correspond more closel y to the parameters of holes localized at group III atoms, in particul ar, at scandium atoms in GeO2. It is concluded that in all centers the scandium atoms occupy silicon sites. (C) 1997 American Institute of P hysics.