Adsorption of atomic oxygen on GaAs(001)-(2×4) and the resulting surface structures

The naturally occurring oxide of GaAs has a high density of defects that pin the Fermi level at the GaAs surface. The principle electronic defect causing the Fermi level pinning is widely believed to be an arsenic antisite double donor. We have used scanning tunneling microscopy to show that the arsenic antisite defects are formed during the initial period of oxidation of GaAs(001) by atomic oxygen. Atomic oxygen displaces a single arsenic atom …