Porous Si anisotropy from photoluminescence polarization

Abstract

We report the observation of the anisotropic linear polarization of porous Si photoluminescence measured in two excitation geometries. In the normal excitation geometry (exciting beam normal to the sample (100) surface) linear luminescence polarization of as much as 20% is seen parallel to the excitation polarization. In the edge excitation geometry (exciting light incident on a cleaved edge of the sample) the luminescence polarization is aligned mainly in the [100] direction (normal to the surface). The effect is described within the framework of a dielectric model in which porous Si is considered as an aggregate of slightly deformed, elongated and flattened, dielectric elliptical Si nanocrystals with preferred orientation in the [100] direction.