We have studied the theoretical and experimental properties of InAs/AlSb/GaSb based type-II superlattice (T2SL) pin photodetector called N-structure. Electronic properties of the superlattice such as HH-LH splitting energies was investigated using first principles calculations taking into account InSb and AlAs as possible interface transition alloys between AlSb/InAs layers and individual layer thicknesses of GaSb and InAs. T2SL N-structure was optimized to operate as a MWIR detector based on these theoretical approaches tailoring the band gap and HH-LH splitting energies with InSb transition layers between InAs/AlSb interfaces. Experimental results show that AlSb layers in the structure act as carrier blocking barriers reducing the dark current. Dark current density and RoA product at 125 K were obtained as 1.8 x 10(-6) A cm(-2) and 800 Omega cm(2) at zero bias, respectively. The specific detectivity was measured as 3 x 10(12) Jones with cut-off wavelengths of 4.3 mu m at 79 K reaching to 2 x 10(9) Jones and 4.5 mu m at 255 K. (C) 2014 Elsevier Ltd. All rights reserved.