Wet chemical etching of InAs-based InAs/Ga（As）Sb superlattice long wavelength infrared photodiodes was studied in this paper. The etching experiments using citric acid, orthophosphoric acid and hydrogen peroxide were carried out on InAs, GaSb bulk materials and InAs/Ga（As）Sb superlattices with different solution ratios. An optimized etching solution for the InAs-based superlattices has been obtained. The etched surface roughness is only 1 nm. InAs-based superlattice LWIR detectors with 50 % cut-off wavelength of 12 μm were fabricated. The photodetectors etched with optimized solution ratio show low surface leakage characteristic. At 81 K temperature, the surface resistivity ρ_Surface of the detector is 4.4 × 10³ Ωcm.