Influence of Surface States on Electronic Band Structure and Electron Density in InAs Nanowires and InAs Shell Nanowires

Abstract

We report on a theoretical study of the impact of surface states on the electronic band structure and on the electron density in intrinsic cylindrical InAs nanowires and InAs shell nanowires (nanotubes). Solving coupled Poisson and Schroedinger equations we show that the electric field induced by the positively charged donor-type surface states bends the conduction band. For a surface states density above 1012 cm-2 the Fermi level is pinned above the conduction band edge in the vicinity of the neutrality level. Downwards bending of the conduction band leads to the formation of a triangular-shaped n-type channel at the nanowire surface and a square-shaped n-type channel in the nanotube. The square-type profile of the conduction band in the nanotubes enables to reach a higher electron density in comparison with nanowires, if the shell thickness exceeds 15 nm. In nanotubes, the stronger confinement leads to the occupation of only the lowest energy subband, whereas in the triangular well of InAs nanowires typically at least subbands are occupied.