Analysis of M-Superlattice structures for infrared photodetection

Type-II Superlattices (T2SL) comprising of InAs/(In,Ga)Sb are currently leading candidates for infrared photodetection. In order to advance the device design, we perform a thorough investigation on the band properties of M-Superlattice (MSL) structures as well as the microscopic properties using the Keldysh non-equilibrium Green's function (NEGF) technique. Using the 8-band k.p method with the envelope function approximation which includes the microscopic interface asymmetry (MIA) and strain effects, we demonstrate the effects of AlSb width on the band edge variations and density-of-states (DOS) effective masses for varied constituent material widths covering the MWIR-LWIR range. Delving into the microscopic properties such as the miniband formation and transmission properties, we depict the advantage of using MSL over T2SL as an absorber as it provides larger interband overlap at the interface for better optical properties. Further comparisons on these structures are made by inspecting in detail the dark current tunneling transport with the inclusion of scattering processes via the momentum dephasing model within the NEGF technique. Furthermore, with the help of local density of states obtained from NEGF, we introduce two MSL configurations that provide reasonable conduction band and valence offsets for a particular T2SL absorber configuration.