A study of broad band photoluminescence from Si 1-xGe x⧸Si superlattices

Abstract

Using photoluminescence (PL) obtained with ultraviolet (UV) laser excitation, we have examined Si 1- x Ge x ⧸Si long-period superlattices (SLs) grown by molecular beam epitaxy at 500°C and annealed post-growth at 550 to 750°C. Our as-grown samples show broad PL bands, 120 meV below the band gap when the effects of quantum confinement of holes are added in. The broad PL band peak positions shift to higher energies as the anneal temperature increases. This coincides with a reduction in the activation energies of the broad PL bands. The broad bands from both the as-grown and annealed samples shift to lower energies as the sample temperature increases.