Probing nanoscale potential modulation by defect-induced gap states on GaAs(110) with light-modulated scanning tunneling spectroscopy

摘要

We investigated charged defects on an n-GaAs(110) surface using light-modulated scanning tunneling spectroscopy. Tunneling via a single defect-induced gap state under photoillumination was observed for the isolated atomic defects. Screened Coulomb potentials induced around a charged Ga vacancy and a step edge were visualized, for the first time, with a nanometer spatial resolution. Furthermore, the charge states of the individual defects were determined on the atomic level.