Raman spectroscopy of Si1-xGex epilayers

The first systematic investigation of the vibrational properties of epitaxial Si1-xGex alloys in the entire composition range (0<=x<=1) is presented. Reciprocal Space Mapping measurements and a Raman spectroscopy study have been undertaken on alloys grown by LowEnergy Plasma Enhanced Chemical Vapour Deposition (LEPECVD) in order to investigate the phonon mode frequency dependence on structural and elastic parameters. It is concluded that the strain relaxation process in the LEPECVD virtual substrates is very effective in the entire composition range and that in these fully relaxed epitaxial SiGe alloys the presence of ordering effects and of local composition fluctuations can be excluded.