Si donors (SiGa) in GaAs observed by scanning tunneling microscopy

Abstract

We report the direct observation of SiGa donors in the top six layers of GaAs(110). Surface SiGa has a localized electronic feature due to its dangling bond, while subsurface SiGa produces delocalized protrusions in filled and empty state scanning tunneling microscopy images, with a full width at half-maximum of ∼25 Å and a height from ∼0.2 to 2 Å, depending on the sample bias and location under the surface. The delocalized features of subsurface SiGa can be understood in terms of the perturbation of the local band structure by the Coulomb potential of SiGa.