Observation of bulk defects by scanning tunneling microscopy and spectroscopy: Arsenic antisite defects in GaAs

The scanning tunneling microscope is used to study arsenic-related point defects in low-temperature-grown GaAs. Tunneling spectroscopy reveals a band of donor states located near ${\mathit{E}}_{\mathit{v}}$+0.5 eV arising from the defects. Images of this state reveal a central defect core, with two satellites located about 15 Å from the core. The structure of the defect is found to be consistent with that of an isolated arsenic antisite defect (As on a Ga site) in a tetrahedral environment.