Electronic structure and optical properties of InAs/GaSb/AlSb/GaSb superlattice

摘要

The electronic structure and optical properties of InAs/GaSb/AlSb/GaSb superlattice (M-structure) are investigated in the framework of eight-band effective-mass theory, with the interface potential considered. The calculated energy gaps agree excellently with the experimental results. Via calculations, we find that the electronic structure of M-structure strongly depends on the geometrical structure of superlattice. The electron effective mass increases notably with the thickness of GaSb and AlSb layers, and AlSb layer is more favorable to obtain large electron effective mass than GaSb layer. Increased thickness of AlSb layer also leads to larger variation range of valence band maximum (VBM) and so M-structure has more tunable VBM than InAs/ GaSb superlattice. Also the VBM of M-structure rises considerably with the increment of GaSb layer thickness and is almost independent of InAs layer thickness. We further find that M-structure has no remarkable superior optical absorption coefficient over InAs/GaSb superlattice. However, with larger electron effective mass and more tunable valence band maximum compared with InAs/ GaSb superlattice, M-structure can be used as barrier in InAs/GaSb superlattice infrared detector to reduce the dark current. And the quantum efficiency of infrared photodiodes will not depend on the bias voltage when the M-structure is appropriately doped and carefully designed based on the dependence of its electronic structure on the superlattice geometry.