Pressure dependence of deep electronic levels in semiconductors: Phosphorus-vacancy pair (or SiEcenter) and divacancy in silicon

The effects of hydrostatic pressure on the electron thermal emission rates and capture cross sections of three deep electronic levels in phosphorus-doped silicon were investigated. Included were the $E_c$-0.44 eV acceptor associated with the phosphorus-vacancy pair defect (or Si E center), the $E_c$-0.23 eV acceptor associated with the 2 -/- charge state of the divacancy, and a level of uncertain origin at $E_c$-0.40 eV. The results allow determination of the shift of the energies of these levels with pressure and of the breathing-mode lattice relaxations which accompany electron emission and capture by these levels. This is the first determination of these properties. For the phosphorus-vacancy acceptor, pressure shifts the level deeper into the band gap, and an outward (inward) volume relaxation accompanies electron emission (capture). These results can be qualitatively understood in terms of the accepted model for this defect and the bondinglike nature of its level. Qualitatively similar results are obtained for the $E_c$-0.40 eV level, but opposite effects are seen for the divacancy level. Specifically, with pressure, this latter level moves higher in the band gap, and the lattice relaxes inward (outward) on electron emission (capture). These results can also be understood in terms of the accepted model for the defect and the antibondinglike nature of its level.