Dielectric effects in the photoluminescence from porous silicon

Polarization dependent photoluminescence (PL), time-resolved PL and PL exci tation experiments are performed in order to clarify the origin of the line ar polarization of the PL of porous silicon excited by lineally polarized l ight. It is shown that this effect, when PL is excited significantly above the detection energy, is not related to a coherent exciton alignment or sel ective optical excitation of those nanocrystals whose transition dipole mom ents are oriented parallel to the polarization vector of the exciting light . The experimental results are interpreted in the framework of a dielectric model assuming aspheric nanocrystals.