Using the optical methods of reflection anisotropy spectroscopy, surface photovoltage spectroscopy, and contactless electroreflectance, we have conducted an ex situ investigation of (a) the InP/In0.53Ga0.47As(001) heterojunction interface as a function of InP overlayer thickness (50-1000 nm) and (b) the surfaces of n- and p-doped In0.53Ga0.47As(001). All samples were fabricated by organometallic vapor phase epitaxy. The results from these optical probes make it possible to form a comprehensive quantitative picture of the InP/InGaAs heterojunction, including conduction and valence band offsets of 275 and 325 meV, respectively, as well as the (001) surface of InGaAs(surface Fermi level = 200 mV from the conduction band edge).