Formation of compositionally abrupt axial heterojunctions in silicon-germanium nanowires.

We have formed compositionally abrupt interfaces in silicon-germanium (Si-Ge) and Si-SiGe heterostructure nanowires by using solid aluminum-gold alloy catalyst particles rather than the conventional liquid semiconductor-metal eutectic droplets. We demonstrated single interfaces that are defect-free and close to atomically abrupt, as well as quantum dots (i.e., Ge layers tens of atomic planes thick) embedded within Si wires. Real-time imaging of growth kinetics reveals that a low solubility of Si and Ge in the solid particle accounts for the interfacial abruptness. Solid catalysts that can form functional group IV nanowire-based structures may yield an extended range of electronic applications.