Observation of cleaved GaAs (110) surfaces is performed by scanning tunneling microscopy in ultrahigh vacuum. Monoatomic steps and anomalously large corrugation regions of a few tens of square angstroms in the atomically flat terrace are observed. Since the number of the large corrugations corresponds to the number of the dopant within a few atomic layers, these corrugation regions are probably induced by the dopant. Voltage-dependent morphology, which originates from the local density of states of each constituent at the surface, is also discussed.