GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy

Abstract

a b s t r a c tAmmonia-based molecular beam epitaxy (NH 3 -MBE) was used to grow catalyst-assisted GaN nanowires on ð1102Þ r-plane sapphire substrates. Dislocation free ½1120 oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar f1010g side facets, which appear due to a decrease in relative growth rate of the f1010g facets to the f1011g and f1011g facets under the growth regime in NH 3 -MBE. Compared to GaN nanowires grown by Ni-catalyzed metal-organic chemical vapor deposition, the NH 3 -MBE grown GaN nanowires show more than an order of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.

Morphology and composition controlled growth of polar c-axis and nonpolar m-axis well-aligned ternary III-nitride nanotube arrays

“…The growth rates of the (0001 ˉ), nonpolar, and semipolar facets are much lower than that of the (0001) facet, leading to the appearance of these facets in the m-axis nanostructures. 57,58 For a more clear view, a schematic illustration of the nanotubes on the r-plane sapphire is shown in Fig. 5d.…”