Atomically precise delineation of As antisite defect states from undoped gallium arsenide host lattice by STM/STS measurements and DFT calculations

Using a combination of scanning tunneling microscopy (STM) and spectroscopy with density functional theory calculations, we unambiguously delineate the electronic properties of the sub-surface arsenic antisite defect (AsGa) from those of the surrounding As atoms in undoped gallium arsenide (GaAs) lattice with atomic precision. In the GaAs(110) surface with AsGa located at the second layer (2-AsGa), we found that the mid-gap state induced by 2-AsGa manifests as a bright contrast at the AsGa-As bond site. Furthermore, we show that STM images taken at large magnitudes of negative sample bias are dominated by the local density of states of neighboring surface As atoms. These states lead to a four-lobe symmetric contrast in the filled state STM image around the 2-AsGa defect. These results provide insights for surface/sub-surface defect engineering at the atomic scale. This article is protected by copyright. All rights reserved.