Structural properties and energetics of GaAs nanowires

Using the first-principles density functional theory, we have investigated the geometric structure and electronic properties of GaAs nanowires. Compared with bulk GaAs, wurtzite nanowires are found to be more stable over zinc-blende nanowires. A revised cohesive energy is provided based on the influence of different kinds of surface dangling bonds. Our calculation indicates that GaAs nanowires display bistability namely both zinc-blende and wurtzite nanowire will form around 90 Å diameters. Furthermore, most GaAs nanowires are found to be semiconducting except for the zinc-blende nanowires. In zinc-blende nanowires, it is mainly due to the twofold coordinated atoms associated with the surface state will decrease the band gap. Upon H passivation, these nanowires become semiconducting and the trend of the band gap decreases with the diameter increases.