Facet and in-plane crystallographic orientations of GaN nanowires grown on Si(111)

We have determined the in-plane orientation of GaN nanowires relative to the Si ( 111) substrate on which they were grown. We used x-ray diffraction pole figure measurements to evidence two types of crystallographic orientation, all the nanowires having {10 (1) over bar0} lateral facets. The proportion of these two orientations was determined and shown to be influenced by the pre-deposition of Al(Ga)N intermediate layers. In the main orientation, the GaN basal < 10 (1) over bar0 > directions are aligned with the Si < 110 > directions. This orientation corresponds to an in-plane coincidence of GaN and Si lattices.