Band engineered epitaxial Ge--Si[sub x]Ge[sub 1 - x] core-shell nanowire heterostructures

We report the growth of germanium (Ge)—silicon-germanium (SixGe1−x) epitaxial core-shell nanowire (NW) heterostructures, with tunable Si and Ge shell content. The Ge NWs are grown using the vapor-liquid-solid growth mechanism, and the SixGe1−x shells are grown in situ, conformally on the Ge NWs using ultrahigh vacuum chemical vapor deposition. We use transmission electron microscopy to demonstrate epitaxial shell growth, and scanning energy dispersive x-ray spectroscopy to determine the shell thickness and content. The Si and Ge shell content can be tuned depending on the SiH4 and GeH4 partial pressures during the shell growth, enabling band engineered core-shell NW heterostructures.