Annealing effects in short period Si-Ge strained layer superlattices

Annealing effects in Si/Ge strained layer superlattices (SLS) are studied by Raman scattering. Spectra from optical and folded acoustic phonons are recorded after each temperature treatment. Above 600 degrees C the Ge LO phonon shifts to lower frequencies and the Si-Ge alloy mode gains in intensity due to diffusion of Si into the Ge layers. The Si mode remains unchanged up to annealing temperatures of about 800 degrees C. The intensity ratios of folded LA phonons are also sensitive to the annealing process. Their frequencies shift only slightly. Raman spectroscopy allows the authors to separate a different interdiffusion process of species in adjacent layers.