Structural and electronic properties of [0001] AlN nanowires: A first-principles study.

Using first-principles methods, we investigated the atomic relaxations, electronic structure, and formation energies of nonpassivated AlN nanowires along [0001] directions. We find that all the nanowires prefer to have [formula] lateral facets and all the wires with [formula] lateral facets are semiconductors with a direct band gap. However, surface states that arise from the facet atoms exist inside the bulklike band gap, which can have a large effect on the optoelectronic properties of the nanowires. Our calculated formation energies of the nanowires show that there is a sublinear relationship between the formation energy and surface-to-volume ratio, indicating that the surface effect is localized and becomes more important for small nanowires. [ABSTRACT FROM AUTHOR]