Uniaxial-Stress and Zeeman Measurements on the 943 Mev Luminescence Band in Silicon

The photoluminescence from silicon lightly doped with copper and rapidly quenched from ~ 1100° C is dominated by a vibronic band with zero--phonon lines (ZPL) in the region of 943 meV. We have studied the effect of external fields on the electronic properties of this band and the results are consistent with the luminescence occurring at a defect with Td symmetry. The Zeeman measurements indicate that the luminescence is due to the recombination of excitons in J = 1, J = 2 states with the normal ordering of these levels reversed. This reversal is explained by the different response of these states to hydrostatic strains, and it is also argued that strain at the defect provides the binding potential for the exciton.