Polarization memory induced by polarized light-assisted anodization of n-type Si

Abstract

We report a study on the polarization memory effect in n-type, microporous Si anodized in the presence of above-bandgap light. Using unpolarized light, the memory effect parameter ϱ=(I∥−Iτ)/(I∥+Iτ) is quite small, reaching values of only 5% at the upper end of the photoluminescence (PL) band extending to 2.3 eV for excitation with 3.8 eV light. When the same anodization is carried out under linearly polarized light, the value of ϱ increases fourfold to ∼20% at 2.3 eV. The enhancement is maximal when the PL is excited with the linear polarization aligned with direction of that of the etching illumination. A well-defined anisotropy of ϱ in the (100) sample plane is found tied to the polarization direction of the etching light and independent of the crystal axes ([100] or [110]). We discuss these observations in terms of a texture of the porous layer with preferential alignment induced by the polarized light-assisted etching.