A comparison of the properties of porous silicon formed on polished and textured (1 0 0) Si: High resolution XRD and PL studies

Porous silicon (PS) layers formed by anodization on polished and textured substrates of (1 0 0) Si at different current densities for a fixed anodization time of 30 min have been characterized by high resolution X-ray diffraction (HRXRD), and photoluminescence (PL) techniques. Porosity and thickness of PS layers were estimated by gravimetric analysis. PS layers and their interfaces have been characterized by recording topographs, diffraction curves, measuring lattice mismatch/strain and the radius of curvature due to induced biaxial stress caused by the lattice expansion of PS film due to pores. The strain in PS films formed on textured substrates varies linearly upto larger current densities without elastic relaxation. Porosity and strain measurements made on both the types of PS films show that stable and highly porous PS films having different strain values corresponding to wide range of band gaps can be formed on textured substrate. PS films formed on textured substrate show higher PL intensity and higher life time values as compared to those formed on polished substrates for the same current density. The present studies indicate that the structural, mechanical and optical properties of thick PS films formed on textured samples are superior to that formed on polished specimens.