Abstract
A detailed structural and optical investigation of several porous Si-Ge samples has been performed. Raman spectroscopy indicates phonon confinement in two classes of nanostructures; small Ge particles (2–3 nm) and larger Si-Ge particles (less than 6 nm). The photoluminescence reflects this distribution of nanoparticles showing blue-green and red emission. Decay times for blue green photoluminescence are of the order of 100 ns while, for the red emission, times one order of magnitude lower than in porous Si are found.