Crystal Phase Selective Growth in GaAs/InAs Core-Shell Nanowires

We present a novel type of core-shell nanowires in which only certain parts of the core are covered by the shell. This is achieved by the crystal phase selective growth of the In As shell on zinc blende GaAs nanowires with controlled wurtzite inclusions. The shell grows on the zinc blende phase, but its growth is hindered on the wurtzite crystal phase. Nucleation of In As occurs exclusively on the zinc blende GaAs regions. The wurtzite segments are placed inside self-catalyzed GaAs nanowires by partially consuming and refilling the Ga droplet. The crystal phase selective growth of In As on the side facets of the GaAs nanowires is explained by the local environment of each new In atom. Because of unbalanced neighbors on the wurtzite side facets, the growth of a highly lattice mismatched material is hindered. This happens not only on the wurtzite segments, but also on regions being characterized by a high density of twins.