OBSERVATION OF POINT-DEFECTS AND DISLOCATIONS ON GAAS (110) BY SCANNING TUNNELING MICROSCOPY

Scanning Tunneling Microscopy has been used to study the penetration of dislocations on the {110} surface of plastically deformed GaAs single crystals (p-type). Only perfect dislocations producing a double atomic step at the surface were observed. The dislocation cores were localized within two lattice constant at the surface. This led to a considerable strain field around the dislocation core, which could be directly seen in the bending of the As rows in front of the dislocation core. As in n-type material no band bending was observed around the dislocation cores. From this it can be concluded that the dislocations do not carry a strong electrical charge. In contrast to this, positively charged point defects on the As sublattice were observed around the dislocation cores, which can be interpreted as As vacancies.