Pressure-sensitive impurity luminescence centres in 6H SiC crystals

An account is presented on the pressure-sensitive impurity centres in hard silicon carbide crystals, characterized by relatively large hydrostatic pressure shifts of the narrow photoluminescence lines belonging to these centres. Two examples of such centres are considered: a quasimolecular centre comprising Ti atom and a centre formed by an impurity atom from the Sc subgroup, most likely Y. In both cases the individual emission lines in the corresponding ABC and abc spectra exhibit considerable blue shifts amounting to 1.08-1.25 meV/kbar for ABC spectrum and 1.68-1.80 meV/kbar for abc spectrum, thus exceeding the red shifts of the well-known R emission lines in ruby (-0.094 meV/kbar) by more than an order of magnitude. For both impurity centres in SiC crystals the pressure-induced quenching of the luminescence is predicted.