Electron energy loss spectroscopy (EELS) is used to obtain direct information on the morphology of Al, In, Se, and Sb overlayers deposited on GaAs(110). We study particularly the 20.0 eV GaAs surface exciton (SE), a transition which involves the surface Ga empty dangling bond, and correlate its amplitude with the continuity of the deposited layer. We confirm the results obtained for these interfaces with Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) and demonstrate that the SE peak can be used as a highly sensitive indicator of effective surface coverage.