  Zinc phosphide, Zn3P2, nanowires constitute prospective building blocks for
next generation solar cells due to the combination of suitable optoelectronic
properties and an abundance of the constituting elements in the Earths crust.
The generation of periodic superstructures along the nanowire axis could
provide an additional mechanism to tune their functional properties. Here we
present the vapour-liquid-solid growth of zinc phosphide superlattices driven
by periodic heterotwins. This uncommon planar defect involves the exchange of
Zn by In at the twinning boundary. We find that the zigzag superlattice
formation is driven by reduction of the total surface energy of the liquid
droplet. The chemical variation across the heterotwin does not affect the
homogeneity of the optical proerties, as measured by cathodoluminescence. The
basic understanding provided here brings new perspectives on the use of II-V
semiconductors in nanowire technology.
