N-structure based on InAs/AlSb/GaSb superlattice photodetectors

• N-structure is a new design of barrier infrared detector.
• The structure is based on InAs/AlSb/GaSb based type-II superlattice system.
• HH–LH splitting energies are calculated for AlSb and InSb interfaces.
• AlSb barriers perform enhanced e–h overlaps leading to higher detectivity.
• Electrical and optical results are promissing for high temperature applications.

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 R0A product at 125 K were obtained as 1.8 × 10−6 A cm−2 and 800 Ω cm2 at zero bias, respectively. The specific detectivity was measured as 3 × 1012 Jones with cut-off wavelengths of 4.3 μm at 79 K reaching to 2 × 109 Jones and 4.5 μm at 255 K.