[en] Highlights: • Passivation causes increase of the surface band bending of InN by 0.7–0.8 eV. • Sulfide passivation causes increase in photoluminescence intensity of InN. • Passivation causes increase in red light induced photovoltage of InN. • Electronic properties of passivated InN remain stable for 20 months of the air exposure. - Abstract: Surface electronic properties of the native-oxide-covered and sulfide-passivated InN grown on the Si(111) substrate were studied by photoemission spectroscopy induced by synchrotron radiation, as well as by photoluminescence and atomic-force microscopy. It was found that the treatment of the native-oxide-covered InN surface with the solution of ammonium sulfide in 2-propanol results in the increase of the surface band bending by 0.7–0.8 eV. Sulfide passivation causes increase in the photoluminescence intensity of InN, as well as the appearance of the photovoltage induced by illumination with red light, which is the evidence of the reduction of the surface recombination velocity due to sulfide passivation. These improved electronic properties remain stable for at least 20 months of the exposure in air.