Interpretation of GaAs(110) scanning tunneling microscopy image contrast by the symmetry of the surface Bloch wave functions

A simple qualitative correlation between the corrugation anisotropy observed in scanning tunneling microscope (STM) images of GaAs(110) surfaces and the symmetry properties of the surface states is presented. We show that as a function of bias, tunneling from different electronic states near high-symmetry points of the surface Brillouin zone gives rise to a distinct corrugation along [11̄0] and [001] in STM images. Existing models of the surface band structure are used to identify these states. We show that at small bias, due to band bending effects, the same surface state near the conduction-band edge determines the image corrugation in both filled and empty states images of n-type GaAs.