True bulk As-antisite defect in GaAs(1 1 0) identified by DFT calculations and probed by STM/STS measurements.

• The third layer As-antisite defect in GaAs(1 1 0) mimics that of bulk GaAs. • STM image from experiment and theory present a unique asymmetric two-lobe contrast. • Calculated LDOS and STS spectra reveal three prominent peaks as surface signatures. We reveal the As-antisite (As Ga) defect close to the surface of GaAs(1 1 0) with bulk characteristics using first-principles methods with experimental verifications. We found that the As Ga in the third-layer mimics the geometry, partial charge density and more importantly, the density of states of As Ga in bulk GaAs. Notably, the mid-gap state induced by As Ga in bulk GaAs is well-reproduced by the As Ga in the third layer of GaAs(1 1 0). Simulated and experimental STM images show an "asymmetric two-lobe" feature in the region around the defect. Using local density of states (LDOS) and STS spectra, we propose three prominent peaks with characteristic energy levels corresponding to the third layer As Ga. The above results present the first report of surface electronic signatures of true bulk defect near the surface of GaAs(1 1 0). [ABSTRACT FROM AUTHOR]