Hierarchical self-assembly of epitaxial semiconductor nanostructures

We describe a new route to hierarchical assembly of semiconductor nanostructures, employing guided organization of self-assembling epitaxial quantum dot molecules in the Ge _xSi _1-x/Si(100) system. The quantum dot molecule comprises a shallow strain relieving pit, defined by {105} facets, and bounded by 4-fold {105}-faceted islands. Through topographic "forcing functions" fabricated on the substrate surface, the quantum dot molecules may be organized into arrays, enabling hierarchical structures spanning length scales from tens of nanometers to macroscopic dimensions.