Variations of interfacial roughness with epilayer thickness and scaling behavior in Si_1-xGe_x grown on Si(100) substrates

Roughness parameters of sample surface and buried interfaces in a series of thin layers of Si_0.4Ge_0.6 grown on Si(100) by molecular beam epitaxy (MBE) were measured by using the technique of grazing-incidence x-ray scattering (GIXS). The strain in the layer and the critical thickness of the film were determined from x-ray diffraction of the Si(004) peak. The roughness parameters can be described by a scaling-law with an exponent β = 0.71 for both the surface and interfacial roughness. Establishment of a scaling law thus allows a possibility of predicting the interfacial roughness as a function of the epilayer thickness.