SULFUR-RELATED METASTABLE LUMINESCENCE CENTER IN SILICON

Optical detection of magnetic resonance; (ODMR) and photoluminescence (PL) studies are described for the sulfur-related metastable defect in silicon first reported by Brown and Hall. It is established that its two configurations, A and B, are of triclinic (C-1) symmetry, and the incorporation of a single impurity atom with nuclear spin I= 3/2 is co nfirmed directly by resolving its hyperfine structure in each ODMR spe ctrum. Detailed study of the conversion kinetics indicates the dominan t A-->B mechanism under below band-gap excitation to be the result of direct optical excitation, not the result of exciton capture or the en ergy release accompanying the luminescence. The barrier for thermally activated B-->A return is 0.10+/-0.02 eV, with no evidence of an inter mediate configuration. Stress-induced splittings of the PL are satisfa ctorily analyzed as the sum of that for a highly localized hole plus t hat for a shallow Coulombically bound effective-mass electron. A:tenta tive model is proposed involving a substitutional sulfur atom paired w ith an interstitial copper atom in two different nearby configurations . The low symmetry results from the tendency of the Cu interstitial to go off-center from the tetrahedral interstitial position.