OPTICAL PHONON PROBES OF THE LATERAL SCALE OF INTERFACE ROUGHNESS - ATHEORETICAL INVESTIGATION

We study the effect of the different lateral scale of interface roughn ess on the optical photon spectrum of thin Si/Ge (001) superlattices. We find that the first Si-like confined optical mode does localize eit her in the thinnest or in the thicker part of the Si well already for relatively small lateral sizes of the interface terraces, contrary to the corresponding behaviour in GaAs/AlAs structures. We show that this gives rise to distinct changes in the Raman lineshape, which should b e useful to discriminate between short-range intermixing and long-rang e interface corrugation in Si/Ge superlattices. We finallyy discuss th e optimal conditions to allow experimental observations of this effect .