The type-2 InAs/InAs1-xSbx superlattices on GaAs substrate with GaSb buffer layer were investigated by comparison of theoretical simulations and experimental data. The algorithm for selection of input parameters (binary and ternary materials) for simulations is presented. We proposed the method of the bandgap energy extraction of the absorption curve. The correct choice of the bulk materials and bowing parameters for the ternary alloys allows to reach good agreement of the experimental data and theoretical approach. One of the key achievements of this work was an electron affinity assessment for the device's theoretical simulation. The detectivity of the long-/very long-wave InAs/InAs1-xSbx superlattice photoconductors at the level of ~ 8 x 10(9) cm Hz(1/2)/W (cutoff wavelength 12 mu m) and ~ 9 x 10(8) cm Hz(1/2)/W (cutoff wavelength 18 mu m) at a temperature 230 K confirmed the good quality of these materials.