Quantum confined luminescence in Si/SiO2 superlattices

Amorphous Si/SiO2 superlattices with periodicities between 2 and 5 nm have now been grown on (1 0 0) Si wafers by several different techniques: molecu lar beam epitaxy, magnetron sputtering, and plasma enhanced chemical vapor deposition (PECVD). With the first two methods little or no hydrogen is inc orporated during growth and visible photo-luminescence (PL) is obtained at wavelengths from 520 to 800 nm. The shift in the PL peak position with Si l ayer thickness is consistent with quantum confined band-to-band recombinati on. Annealing the sputtered superlattices at temperatures up to 1100 degree s C results in avery bright red PL that is similar in intensity to that obs erved in porous Si samples. For large numbers of periods (e.g., 425) the PL is strongly modulated in intensity owing to optical interference within th e superlattice. Similar quantum confined, but defect induced, PL is also ob served in the PECVD grown superlattices, where the amorphous Si layers are heavily hydrogenated.