A structure comprised of an InAsSb layer adjacent to a GaSb layer, with the adjacent InAsSb and GaSb layers repeating to form a superlattice (SL). The structure is preferably an unstrained SL, wherein the composition of the InAsSb layer is InAs0.91Sb0.09; the InAs0.91 Sb0.09 layers are preferably lattice-matched to the GaSb layers. The SL structure is preferably arranged such that the Sb component of the InAsSb layers reduces the strain in the SL structure so that it is less than that found in an InAs/GaSb Type-II Strained Layer Superlattice (SLS). The present SL structure is suitably employed as part of an infrared photodetector.