Theoretical analysis on the energy band properties of N- and M-structure type-II superlattices

The electronic band structure of conventional InAs/GaSb superlattices (SLs), N- and M-structure were investigated by 8-band k·p method. A good agreement between the theoretical calculation and experimental results was obtained. Compared with the conventional structure, the band gap and effective mass of N- and M-structure both increased with the thickness of AlSb layers raising. The splitting energy between first heavy hole band (HH1) and first light hole band (LH1) increased in N-structure, but firstly raised and then reduced in M-structure. The impact of changing the position of AlSb barrier in M-structure is also studied. By altering the position of the barrier layer, the wave function overlaps can be controlled at the InAs/GaSb or GaSb/InAs interface in PN junction. By comparing the three type SLs, we found that N- and M-structure can obviously suppress dark current and enhance wave function overlap. Besides, M-structure can be more alternative in structure design.