INTERFACIAL MICROSTRUCTURES OF ULTRATHIN GE LAYERS ON SI PROBED BY X-RAY-SCATTERING AND FLUORESCENCE YIELD

Angular dependence of grazing-incidence x-ray scattering and Ge Kalpha fluorescence yield were measured for buried ultrathin Ge layers grown on bulk Si by molecular beam epitaxy. Results obtained for samples wi th different Ge layer thickness are compared. The data reveal informat ion on microstructures in these layered materials in terms of the aver age interfacial roughness, correlation lengths of height fluctuations, and Ge density profile. Structural parameters are obtained by compari son of experimental data with theoretical models. The results also ind icate that the interfacial roughness at neighboring interfaces is high ly correlated. Significant changes of microstructures in the Ge epilay er are found as the layer thickness approaches the critical thickness. The x-ray scattering techniques are demonstrated to be capable of det ecting a precursor of lattice relaxation in multilayers of lattice-mis matched compound semiconductors.