Abstract
Ab initio pseudopotential calculations of C and Si impurity atoms on an As-terminated GaAs(001) surface have been performed. First, the C atom is found to stay near a midpoint between the As atoms on the surface and the Si atom a cation site. Secondly, we find that the C atom is more strongly bound to the GaAs surface than the Si atom. Geometrically as well as energetically, the C atom is more difficult to remove from the GaAs surface. The present results agree with an experimental fact that in contrast with the case of Si, eliminating the C impurity through the surface requires thermal etching at such a high temperature of 750°C.
