All-porous silicon-coupled microcavities: Experiment versus theory

A detailed study of coupled porous silicon (PS) microcavities (PSM's) is re ported. The samples are investigated by room temperature photoluminescence and reflectivity. A splitting of the eigenmodes of the coupled cavity struc ture is observed, as well as a difference between the intensities of the ca vity peaks related to mismatch between the two cavity thicknesses. The resu lts are interpreted by a transfer matrix calculation of the optical respons e of the PSM, where the single PS layer is modeled by Si nanocrystals with a distribution of sizes. Comparison of calculations and experiments allows us to deduce the PS oscillator strength at the band gap. The oscillator str ength per cell is found to be f(cell)similar to 4x10(-5), i.e., small, whic h is consistent with the interpretation of the visible photoluminescence of PS as being due to indirect transitions of quantum confined electrons in S i nanocrystals. [S0163-1829(98)02139-0].