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

Abstract

We reveal the As-antisite (AsGa) defect close to the surface of GaAs(1 1 0) with bulk characteristics using first-principles methods with experimental verifications. We found that the AsGa in the third-layer mimics the geometry, partial charge density and more importantly, the density of states of AsGa in bulk GaAs. Notably, the mid-gap state induced by AsGa in bulk GaAs is well-reproduced by the AsGa 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 AsGa. The above results present the first report of surface electronic signatures of true bulk defect near the surface of GaAs(1 1 0).