Anisotropy investigations and photoluminescence properties of porous silicon

Porous silicon layers have been investigated using reflectance and photoluminescence techniques at room and liquid nitrogen temperatures. We observe a noticeable anisotropy of porous silicon samples. The measured parallel and normal components of the refractive index for samples with moderate porosity were 1.25 and 1.30, respectively. Possible mechanisms for the origin of the photoluminescence are discussed.