Oscillating contrast in room-temperature scanning tunneling microscope images of localized charges in III-V semiconductor cleavage surfaces

Positively and negatively charged defects and dopant atoms in n-doped GaAs(110) surfaces give rise, at room temperature, in occupied-state scanning tunneling microscope images to a bright elevation, which is surrounded by a dark depression ring. This oscillating contrast is not observed in empty-state images. A similar effect is found on n-doped GaP(110) surfaces. A simulation of the contrast induced by localized charges on (110) surfaces of III-V semiconductors suggests that the oscillation in room-temperature scanning tunneling microscope images can be explained as the image of the local potential change (screened Coulomb potential) induced by the presence of the charge. (C) 1998 American Vacuum Society. [S0734-211X(98)00105-X].