Electron paramagnetic resonance of the scandium acceptor in 4H and 6H silicon carbide

In Sc-doped 6H-SiC epitaxial layers we observed several different electron paramagnetic resonance (EPR) spectra with a Sc-45 hyperfine interaction pat tern. The spectra are explained as being due to the isolated Sc-0(S = 1/2) acceptor on carbon sites but with different microscopic configurations. The spectra show a pronounced temperature dependence. At low temperatures the hole of the Sc-0 acceptor is located in a Sc-0-Si bond either along the c-a xis forming an axial centre or along one of the three other C-Si bonds givi ng rise to a monoclinic centre. At higher temperature the hole changes plac e rapidly between the three Sc-Si bonds resulting in an axial centre. All t hree Sc-0 hole configurations have different ionisation levels. The ionizat ion level of the low-temperature monoclinic-high-temperature axial centre i s significantly influenced by an entropy term. In 4H-SiC spectra were only observed from a single Sc-0 centre with monoclinic symmetry. (C) 1999 Elsev ier Science B.V. All rights reserved.