Effects of dangling bonds and diameter on the electronic and optical properties of InAs nanowires

In this article we explore the effects of dangling bonds and diameter on the electronic properties of the wurtzite InAs nanowires (NWs) using the density functional theory. The NWs are confined in the hexagonal supercell and are simulated in the [0001] direction. The calculations have been carried out by applying the periodic boundary conditions along the NW axis, i.e., z-Cartesian coordinate, providing enough vacuum to isolate the system from its neighbors. The optical properties of a material are directly related to the band-gap; therefore a relationship between the band-gap and diameter of the nanowires is obtained by using two models, where the band-gap for a larger diameter NW can be estimated. The results of these models are compared with each other and the effects of the dangling bonds on the band-gaps are also investigated. The band-gap of the nanowires decreases and the dangling bond ratio increases with the increase in the diameter of the nanowire, and hence we expect that for large diameter nanowires the band-gap will approach the band gap of the bulk material. An interesting feature of the shift in the band-gap from indirect to direct, i.e. optically inactive to active, is also observed in these NWs with the increase in the diameter.