The roughness and the crystallographic orientation selectivity of etched antimonide-based infrared materials are examined and are used to optimize the chemical mesa etching process of the InAs/GaSb superlattice photodiode with the goal of reducing the dark current.The etchant used is based on phosphoric acid(H_3PO_4),citric acid(C_6H_8O_7) and hydrogen peroxide(H_2O_2).The roughness of the mesa sidewalls and etching rates are compared and used to find an optimized etchant,with which we obtain optimized mid-wavelength infrared photodiodes possessing an R_OA value of 466Ω·cm~2 and a detectivity of 1.43 × 10~(11) cm·Hz~(1/2)W~(-1).Crystallographic orientation selectivity is seen in InAs etching,and also is seen in the InAs/GaSb superlattice wet chemical etching process. The roughness and the crystallographic orientation selectivity of etched antimonide-based infrared materials are examined and are used to optimize the chemical mesa etching process of the InAs / GaSb superlattice photodiode with the goal of reducing the dark current. The etchant used is based on phosphoric acid (H_3PO_4), hydrogenric acid (C_6H_8O_7) and hydrogen peroxide (H_2O_2). The roughness of the mesa sidewalls and etching rates are compared and used to find an optimized etchant, with which we can obtain optimized mid-wavelength infrared photodiodes possessing an R_OA value of 466 Ω · cm ~ 2 and a detectivity of 1.43 × 10 ~ (11) cm · Hz ~ (1/2) W ~ .Crystallographic orientation selectivity was seen in InAs etching and also in the InAs / GaSb superlattice wet chemical etching process.