INTERFACIAL ROUGHNESS IN (111)-ORIENTED Si/Si_1-xGe_x MULTILAYERS. J.H. Li, Y. Yamaguchi, P. M. Reimer, O. Sakata, and H. Hashizume, Tokyo Institute of Technology

Interfacial roughness of semiconductor heteroepitaxial structures has been a subject of extensive studies in recent years, driven by the thought that the interfacial roughness might become a crucial limit for high carrier mobility when the quantum well is down-sized to nanometer scales. Characterization of the nature of the interfacial roughness is important both for understanding the physical mechanism involved in roughening and for controlling it. X-ray reflectivity and diffuse scattering measurements are powerful techniques for such studies, due to its high sensitivity to a wide range of length scales (say, from atomic to micrometer order), and its non-destructive nature. Among the previous studies, (001)-oriented Si/Si_1-xGe_x multilayers have received a great attention because its potential applications in infrared detectors and high-speed field-effect transisitors. In this work, x-ray specular reflectivity and diffuse scattering, combined with high-angle Bragg diffraction, were employed to study the interfacial properties of (111)-oriented Si/Si_1-xGe_x multilayers. The samples contain 10 pairs of Si/Si_1-xGe_x layers with a nominal periodicity of 10nm (5nm for each of the two component layers), and x of either 0.1 or 0.3. Interfaces are characterized by a quasi-periodically undulated morphology, which is believed to be originated from the terraced surfaces of the substrates due to an unintentional miscut. Our x-ray results have been compared to atomic force microscopy measurements.