Pressure effects on zero-phonon lines in the impurity photoluminescence spectra of 6 H SiC crystals

Abstract

Comparative data about the effect of hydrostatic pressure up to 10.5 kbar at 77 K on the visible ABC and the near-infrared abc photoluminescence spectra in 6 H SiC crystals are presented. In both spectra rather large pressure shifts of zero-phonon lines and their vibrational replicas towards higher energies are found, the shifts for individual lines ranging from 1.08 to 1.25 meV/kbar in ABC spectrum and from 1.68 to 1.80 meV/kbar in abc spectrum. The pressure shifts and also the calculated hydrostatic deformation potentials for ABC lines exceed in the absolute value by more than 10 times those of the well-known R emission lines in ruby. The high pressure sensitivity of ABC lines is interpreted in terms of a ligand field model for an impurity centre where a Ti atom substitutes a Si atom in the SiC host lattice. Even larger pressure shifts obtained for the near-infrared abc lines are in conformity with an assumption that this emission is due to an impurity atom from the scandium subgroup, most likely yttrium Y.