Quantum confined luminescence in Si/SiO2 superlattices

Superlattices of Si/SiO2 have been grown at room temperature with atomic layer precision using state of the art molecular beam epitaxy and ultraviolet ozone treatment. Photoluminescence was observed at wavelengths across the visible range for Si layer thicknesses 1 < d < 3 nm. The fitted peak emission energy E(eV) = 1.60 + 0.72d(-2) is in accordance with effective mass theory for quantum confinement by the wide-gap SiO2 barriers and also with the bulk amorphous Si band gap. Measurements of the conduction and valence band shifts by x-ray techniques correlate with E(d), confirming the role of quantum confinement and indicating a direct band-to-band recombination mechanism.