Organization of self-assembled quantum dots in SiGe/Si multilayers: effect of strain and substrate curvature

The organization of Ge ‘dome’ islands in Ge/Si multilayers has been investigated by cross-sectional transmission electron microscopy. Ge ‘domes’ are found to spontaneously arrange in oblique stacks, replicating at a well-defined angle from one bilayer to the next. The formation of oblique island stacks is governed by a complex interplay of surface strain—generated by the already buried islands—and surface curvature—caused by the inherent tendency of large ‘domes’ to carve out material from the surrounding planar substrate.