Hexagonal Silicon-Germanium Nanowire Branches with Tunable Composition

Hexagonal SiGe-2H has been recently shown to have a direct bandgap, and holds the promise to be compatible with silicon technology. Hexagonal Si (Ge) has been grown on an epitaxial lattice matched template consisting of wurtzite GaP (GaAs). Here, we present the growth of hexagonal Si and SiGe nanowire branches grown from a wurtzite stem by the Vapor-Liquid-Solid (VLS) growth mode, which is substantiated by <em>in-situ</em> transmission electron microscopy. We show that the composition can be tuned through the whole range of stoichiometry from Si to Ge, and the possibility to realize Si and SiGe heterostructures in these branches.