ON THE ROLE OF GERMANIUM IN POROUS SILICON-GERMANIUM LUMINESCENCE

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