Atomically Precise Delineation of As Antisite Defect States from Undoped Gallium Arsenide Host Lattice by Scanning Tunneling Microscopy and Spectroscopy Measurements and Density Functional Theory Calculations

Using a combination of scanning tunneling microscopy (STM) and spectroscopy with density functional theory calculations, the electronic properties of the subsurface arsenic antisite defect (As-Ga) are unambiguously delineated from those of the surrounding As atoms in undoped gallium arsenide (GaAs) lattice with atomic precision. In the GaAs(110) surface with As-Ga located at the second layer (2-As-Ga), it is found that the midgap state induced by 2-As-Ga manifests as a bright contrast at the As-Ga-As bond site. Furthermore, it is shown 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-As-Ga defect. These results provide insights for surface/subsurface defect engineering at the atomic scale.