The surface recombination velocity (SRV) of minority electrons in a type-II InAs/GaSb superlattice photodiode is quantitatively investigated using the electron beam induced current technique and its value used to evaluate the effects of two different passivation methods. Before passivation, the SRV was determined to be (5.0±0.2)×104cm/s. The SRVs of two samples passivated at room temperature are compared with that of the unpassivated sample. One passivation method, using a neutralized (NH4)2S solution for 60min, reduces the SRV by a factor of 2. The other passivation method, using 4% (NH4)2S solution for 30min, reduces the SRV by more than one order of magnitude.