Vertical alignment of InN- and GaN-based nanopillar crystals grown on a multicrystalline Si substrate

•InN nanocrystals vertically grow on multicrystalline Si by the steering crystal.•At nitrogen-rich conditions, InN nanocrystals randomly grow on the substrate.•The steering crystal is also effective for vertical growth of other nitrides. In this study, alignments of nanopillar crystals consisting of indium nitride (InN) and gallium nitride (GaN) based semiconductors were successfully controlled by inserting “steering” nanocrystals between a multicrystalline Si substrate and nanopillar crystals. The directions of the axes of the nanopillar crystals were vertically aligned owing to the effect of the steering nanocrystals even when the nanopillar crystals were grown in conditions in which the directions of the crystal axes tended to be randomly oriented. This technique will enable the realization of novel optoelectronic devices that use nanopillar-shaped crystals consisting of group-III nitride semiconductors fabricated on various non-single crystalline substrates.