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 peroxidewere 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 ρSurface of the detector is 4. 4 × 103 Ωcm.