The subject invention comprises the realization of a superlattice photodiode with polyimide surface passivation. Effective surface passivation of type-II InAs/GaSb superlattice photodiodes with cutoff wavelengths in the long-wavelength infrared is presented. A stable passivation layer, the electrical properties of which do not change as a function of the ambient environment, nor time, can be realized by a solvent-based surface preparation, vacuum desorption, and the application of an insulating polyimide layer.