Using the scanning tunneling microscope, Au adsorbates are found to bond to Ga atoms on the GaAs(110) surface. A characteristic spectrum of band-gap states is observed for the Au adsorbates. Both donor and acceptor states are seen, and they are identified with the first and second electron states of the Au-Ga bond, respectively.

• Received 1 June 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.1412