Arrangement of GaN nanowires grown by plasma-assisted molecular beam epitaxy on silicon substrates with amorphous Al sub(2)O sub(3) buffers

We report on catalyst-free growth of GaN nanowires (NWs) by plasma-assisted molecular beam epitaxy on Si(111) substrates with a thin amorphous Al sub(2)O sub(3) buffer layers deposited at low temperature by atomic layer deposition. We show that nanowires obtained are homogenously distributed and well aligned with the c-axis perpendicular to the substrate in a similar way as their counterparts grown without the Al sub(2)O sub(3) buffer. However, NWs are twisted nearly randomly and do not show any in-plane alignment with the substrate even for the thinnest (~2 nm) buffer used, which is quite opposite to the behavior observed for NWs grown on a bare silicon.