Electrostatic force microscopy was used to study defects in GaAs films grown on Ge. In the case of GaAs films with surface antiphase boundaries, the surface contact potentials at the antiphase boundaries were 30mV higher than those at the domains. This was due to the surface Fermi level at the antiphase boundaries being pinned closer to the valence band maximum. In the case of a thick film which contained buried antiphase boundaries and wedge-shaped depressions on the surface, it was found that the surface contact potential of the wedge-shaped depressions was 25mV lower than that of the GaAs surface. These wedge-shaped depressions therefore had defect electronic states which were different to those of the antiphase boundaries. It was demonstrated that a new form of electrostatic force microscopy could be used to distinguish different types of defect by measuring variations in the relative surface contact potential.

Electrostatic force microscope studies of surface defects on GaAs/Ge films Q.Xu, J.W.P.Hsu: Journal of Applied Physics, 1999, 85[5], 2465-72