Surface Li effects on the electronic properties of GaAs nanowires: A first principles approach

Abstract

The quest for the improvement of Li-Ion batteries has directed attention towards semiconductor nanostructures, like nanowires. However, the surface interactions and effects of Li on the electronic properties of these nanostcrutures has been less explored. Especially the possible modifications to the properties of GaAs nanowires that arise from having Li on its surface have been seldom studied. In this work, we employed Density Functional Theory to study the effects of surface Li on the electronic properties of H passivated GaAs nanowires grown along the [111] direction. To determinate the isolated effects of Li on either surface Ga or As, only Li bonded to either Ga[GaAsNW_Ga-Li] or As[GaAsNW_As-Li] were considered, and up to 6 Li were placed on the respective nanowire surfaces. The results indicate that the energy gap is a function of the Li concentration, the nanowire diameter and the placement of Li on the nanowire surface. The binding energy is independent of the number of Li on the nanowire surface, where the GaAsNW_Ga-Li has slower binding energies compared to the GaAsNW_As-Li, but the binding energies and band gaps in both cases are high, which would hinder the application of these nanowires in Li ion batteries.