Point defects as result of surface deformation on a GaAs wafer

Scratches on the surface of an undoped semi-insulating GaAs wafer have been produced by a wedge-shaped single diamond grain. The subsurface damage has been analyzed by a positron microprobe. This instrument provides laterally resolved positron annihilation measurements, which are sensitive to lattice defects like vacancies and dislocations. We can clearly identify different regions of damage which have been characterized both by conventional scanning electron microscopy and the positron microbeam. The latter reveals indications of plastic deformation due to the trace of created defects observed. We discuss the possible implications of the observed ductile behavior of GaAs usually known to be brittle at room temperature and under atmospheric pressure. (C) 2003 American Institute of Physics.