Contact angle selection and the related crystal phase of vapor-liquid-solid III-V ternary nanowires

It is well documented that the contact angle of droplets catalyzing the vapor-liquid-solid growth of III-V binary nanowires (NWs) plays the central role in their crystal phase, which can be either cubic zincblende or hexagonal wurtzite. Here, we develop a model for the contact angle selection in III-V ternary NWs. We demonstrate that the stable contact angle of ternary AₓB_1-xC NWs based on group-III intermix increases with their composition x for larger incorporation rates of atoms A relative to B and decreases with x otherwise. This trend is reversed for AₓB_1-xC NWs based on group-V intermix. The effect is due to the total balance of the effective V/III ratio for atomic fluxes entering the droplet and used for NW growth. We present some calculations of the stable contact angles vs composition for AlₓGa_1-xAs, InₓGa_1-xAs, and GaPₓAs_1-x NWs and compare them to the recently obtained crystal phase diagrams. The developed approach unravels the role of NW radius, diffusion lengths of group-III adatoms, incorporation rates of group-V atoms in the contact angle selection, and the related crystal phase change and should be useful for understanding and controlling the crystal phase of III-V ternary NWs by the growth parameter tuning.