Formation of GaAs/GaSb Core-Shell Heterostructured Nanowires Grown by Molecular-Beam Epitaxy

In this paper, we demonstrated the growth of GaAs/GaSb core-shell heterostructured nanowires on GaAs substrates, with the assistance of Au catalysts by molecular-beam epitaxy. Time-evolution experiments were designed to study the formation of GaSb shells with different growth times. It was found that, by comparing the morphology of nanowires for various growth times, lateral growth was taking a dominant position since GaSb growth began and bulgy GaSb particles formed on the nanowire tips during the growth. The movement of catalyst Au droplets was witnessed, thus, the radial growth was enhanced by sidewall nucleation under the vapor-solid mechanism due to the lack of driving force for axial growth. Moreover, compositional and structural characteristics of the GaAs/GaSb core-shell heterostructured nanowires were investigated by electron microscopy. Differing from the commonly anticipated result, GaSb shells took a wurzite structure instead of a zinc-blende structure to form the GaAs/GaSb wurzite/wurzite core-shell heterostructured nanowires, which is of interest to the research of band-gap engineering. This study provides a significant insight into the formation of core-shell heterostructured nanowires.