[en] The effect of 2 MeV electron irradiation on interface states of a Au/Langmuir-Blodgett film/InP MIS diode has been studied. It was found by deep-level transient spectroscopy measurement that a broad peak induced by the interface states decreased significantly after electron irradiation. Moreover the surface photovoltaic measurement showed two orders of magnitude reduction of the surface recombination velocity. All this evidence shows that electron irradiation could reduce the density of interface states between InP and the Langmuir-Blodgett film. (author)