Mercury-related luminescent center in silicon.

Abstract

We report a photoluminescence (PL) study of silicon subject to mercury-ion implantation and subsequent annealing. A luminescence center is observed with a characteristic bound-exciton (BE) spectrum consisting of a narrow no-phonon line at 1067.9 meV and a series of equidistant phonon replicas with a phonon energy of about 8 meV. The effects of the various external perturbations in the photoluminescence experiments, such as variations in temperature and excitation power, are reported. The transient PL results give a thermal activation energy (25 meV) consistent with the temperature dependence of the PL intensity. All PL lines are shown to arise from a single isoelectronic center. The absence of splitting in a magnetic field shows that the PL line is a magnetic singlet, consistent with a tightly bound purely spinlike hole in the BE. The electronic structure can therefore be described as a typical pseudodonor case, where the hole is strongly bound at a level 78.6 meV above the valence band, while the electron is a weakly bound effective-mass-like particle, bound by only 23 meV in the BE state. Although the chemical nature of the center is not yet established, the conditions for formation of the center suggest that this luminescent spectrum is due to a mercury-related-complex defect, possibly also involving carbon.