Isoelectronic bound exciton photoluminescence from a metastable defect in sulphur-doped silicon

Abstract

We establish that two deep photoluminescence (PL) systems in Si:S arise from the decay of isoelectronic bound excitons (IBEs) at two metastable configurations of the constituents of a single defect. Each system has two principal zero-phonon lines. We establish from Zeeman measurements that these lines are associated with an isotropic ( g = 2) spin triplet ( S = 1) lower energy state, with a small spin-forbidden transition probability, and a spin single ( S = 0) higher energy state, from which transitions to the S = 0 crystal ground state are allowed. We show, from temperature-dependent PL measurements, that the transition probability ratio for the higher and lower energy states of the bound excitons is about 1800 for the shallower IBE system and about 3000 for the deeper IBE system. The energy separation of the triplet and singlet states is determined to be about 9 meV from temperature dependence measurements, for both IBE systems, in close agreement with the spectroscopically observed line separations.