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 Ev+0.5 eV arising from the defects. Images of this state reveal a central defect core, with two satellites located about 15 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. © 1993 The American Physical Society.