Ge segregation during the initial stages of Si1-xGex alloy growth.

Segregation of Ge in the ‘‘leading edge’’ of Si1-xGex alloys grown by molecular beam epitaxy is investigated using x-ray photoelectron spectroscopy (XPS). Alloys of 5%, 10%, 20%, and 40% Ge were grown in varying thickness (0–20 nm) at 500 °C to observe segregation during the initial stages of alloy growth. The length of the leading edge was found to decrease with increasing Ge concentration (4.8, 2.8, 2.4, and 2.0 nm, respectively). The amount of segregated Ge was found to increase with Ge concentration. A complete monolayer of Ge was found on the surface for all Ge concentrations and an increasing amount of Ge (20%, 55%, 80%, and 95%, respectively) was found in the second atomic layer. [ABSTRACT FROM AUTHOR]