Characterization of photoluminescent porous Si by small-angle scattering of x rays

Abstract

A microstructural study of high-porosity porous silicon layers formed on lightly P-doped wafers has been performed by x-ray small-angle scattering (SAXS) using the powerful and parallel beam of the synchrotron radiation. When the porosity of the sample is increased from 55% to 85% there is a continuous modification in the shape of the scattering profiles. The silicon skeleton mass fractal dimension decreases continuously. For porosity around 85%, the value for which the sample starts to display a strong photoluminescence at room temperature, there is a large increase in the pore size. The scattering profiles are characteristic of an isotropic three-dimensional structure.