Detailed information on the neutral Si vacancy in 4H- and 6H-type material was obtained by using photoluminescence techniques. The excited states and ground states which were involved in the characteristic luminescence of the defect with no-phonon lines at 1.438 and 1.352eV in 4H-type material, and at 1.433, 1.398 and 1.368eV in 6H-type material were shown to be singlets. The orbital degeneracy of the excited states was lifted by the crystal field for the highest-lying no-phonon lines which corresponded to one of the inequivalent lattice sites in both polytypes. This led to the appearance of hot lines at slightly higher energies. Polarization studies of the no-phonon lines revealed differing behaviours for the inequivalent sites. In strained samples, an additional fine structure of the no-phonon lines was resolved, and splitting was suggested to be due to strain variations in the samples.

Electronic Structure of the Neutral Silicon Vacancy in 4H and 6H Si. M.Wagner, B.Magnusson, W.M.Chen, E.Janzén, E.Sörman, C.Hallin, J.L.Lindström: Physical Review B, 2000, 62[24], 16555-60