The determining factor of a preferred orientation of GaN domains grown on m-plane sapphire substrates

Epitaxial lateral overgrowth in tandem with the first-principles calculation was employed to investigate the determining factor of a preferred orientation of GaN on SiO2-patterned m-plane sapphire substrates. We found that the (1[Image: see text]00)-orientation is favored over the (1[Image: see text]0[Image: see text])-orientation in the region with a small filling factor of SiO(2), while the latter orientation becomes preferred in the region with a large filling factor. This result suggests that the effective concentration determines the preferred orientation of GaN: the (1[Image: see text]00)- and (1[Image: see text]0[Image: see text])-orientations preferred at their low and high concentrations, respectively. Our computational study revealed that at a low coverage of Ga and N atoms, the local atomic arrangement resembles that on the (1[Image: see text]0[Image: see text]) surface, although the (1[Image: see text]00) surface is more stable at their full coverage. Such a (1[Image: see text]0[Image: see text])-like atomic configuration crosses over to the local structure resembling that on the (1[Image: see text]00) surface as the coverage increases. Based on results, we determined that high effective concentration of Ga and N sources expedites the growth of the (1[Image: see text]0[Image: see text])-orientation while keeping from transition to the (1[Image: see text]00)-orientation. At low effective concentration, on the other hand, there is a sufficient time for the added Ga and N sources to rearrange the initial (1[Image: see text]0[Image: see text])-like orientation to form the (1[Image: see text]00)-orientation.