DEFECT PROCESSES IN GAP - IMPLICATIONS FOR THE BEHAVIOR OF EXCITED SURFACE-DEFECTS

We have investigated the different charge states and geometries of the P vacancy and Ga antisite defects in bulk GaP as well as on the GaP(110) surface. Similar behavior is observed for both the bulk and surface. The charged P vacancy V(P)+ exhibits symmetric outward relaxations from the vacancy site while V(P)0 and V(P)- display distortions that lower the symmetry. For the Ga antisite defect (Ga(P)), the neutral Ga(P)0 has a broken-bond configuration with one of its Ga nearest neighbors, while Ga(P)- and Ga(P)2- both have the centered configuration. However, due to their lack of symmetry, the atoms at the surface display a larger distortion. The effects of excitations initially lead to a more positive charge state of the surface defects and subsequently to bond weakening.