The effect of surface states and band bending change on reflectivity of cleaved GaAs(110) and GaP(110)

New accurate surface differential reflectivity data of the GaAs and GaP cleavage faces are presented. Surface state transitions have been detected near 2.9 eV in GaAs(110), while in GaP(110) they appear at 2.8 and 3.5 eV. In both cases a small bulk-like Franz-Keldish effect is superimposed on the surface contribution to differential reflectivity. A method for subtracting this term out is described. The relevance of the present results in the context of the debate on surface excitons is also discussed.