For studying the material properties of nanostructured group IV materials, we have developed a pulsed laser ablation method into inert background gases. SiGe alloy nanocrystallites have possibility of novel band structure engineering by controlling not only compositions but also particle sizes. An ArF excimer laser was focused onto the surface of the powder-sintered SixGe1-x target. During the laser ablation, He gas was introduced into a vacuum chamber and was maintained at a constant pressure. Size distribution of the SixGe1-x ultrafine particles decreases with decreasing composition x under fixed conditions of deposition such as background gas pressure. Raman scattering spectra of the deposited SiGe ultrafine particles show three peaks ascribed to mixed crystalline SiGe after annealing, and the linewidths of the peaks broaden due to the reduced size of the crystallites. The frequencies and intensities of the peaks depend on the composition x. Visible PL spectra have broad peaks from 2.25 eV to 2.10 eV, at room temperature. The peak positions show blue shifts with increasing x. Electroluminescent diodes with the Si0.8Ge0.2 nanocrystallite active region were fabricated, and emit visible high peaked at around 1.8 3V, at room temperature.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.