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Pseudomorphic planar III-V transition layers greatly facilitate the epitaxial integration of vapor liquid solid grown III-V nanowires (NW) on Si(111) substrates. Heteroepitaxial (111) layer growth, however, is commonly accompanied by the formation of rotational twins. We find that rotational twin boundaries (RTBs), which intersect the surface of GaP/Si(111) heterosubstrates, generally cause horizontal NW growth and may even suppress NW growth entirely. Away from RTBs, the NW growth direction switches from horizontal to vertical in the case of homoepitaxial GaP NWs, whereas heteroepitaxial GaAs NWs continue growing horizontally. To understand this rich phenomenology, we develop a model based on classical nucleation theory. Independent of the occurrence of RTBs and specific transition layers, our model can generally explain the prevalent observation of horizontal III V NW growth-in lattice mismatched systems and the high crystal quality of horizontal nanowires.
iii-v on silicon; preferential interface nucleation; transition layer; nucleation model; nanowire growth directions; planar nanowires; 3d twinning