How Do Surface and Edge Effects Alter the Electronic Properties of GaN Nanoribbons?

Density functional theory computations were performed to investigatethe surface and edge effects on the structural and electronic properties of wurtzite GaN nanoribbons. For 2D GaN sheets terminated with (0001) direction, the surface effect is dominant and leads to a semiconductor-to-metal transition in both bare and surface hydrogenated GaN sheets. To investigate the edge effects, we constructed the 2D infinitely thick GaN nanoribbons with fixed (0001) crystal orientation to exclude the surface states, and such ribbons are always nonmagnetic semiconductors for both bare and hydrogenated systems, regardless of the edge shapes (armchair or zigzag). Two representative models for ID GaN nanoribbons with finite width and thickness, namely, 7-bilayer 13-armchair and 9-zigzag GaN nanoribbons, were studied, which exhibit versatile electronic properties and variable band structures. These tunable properties could be extrapolated to wider (thicker) ribbons. Therefore, the surface effect, edge effect, and quantum size effect are three important factors that significantly alter the electronic properties of GaN ribbon systems.