NOVELTY - A superlattice structure, comprises: a layer comprising indium arsenic antimonide (InAsSb); and a layer comprising gallium antimonide (GaSb) adjacent to the InAsSb layer; the adjacent InAsSb and GaSb layers repeating to form a superlattice structure, the composition of the InAsSb layer such that the superlattice structure is an unstrained superlattice structure.    USE - A superlattice structure for use as a portion of an IR photodetector (claimed), as well as, superlattice-based photodetectors, superlattice semiconductor lasers, thermoelectric power generators, or thermoelectric coolers.    ADVANTAGE - The superlattice structure provides lower dark currents and is easier to grow than other structures. Substituting InAs0.91Sb0.09 for InAs in an InAs/GaSb superlattice provides better lattice spacing and thus less net strain, thus introducing lesser dark current-increasing defects into the crystal. The present structure could potentially be used to provide IR detectors that perform better than conventional mercury cadmium telluride (HgCdTe) detectors, while also having a higher operating temperature.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for an IR photodetector, comprising: an absorber layer, comprising: a layer comprising InAsSb; and a layer comprising GaSb adjacent to the InAsSb layer; the adjacent InAsSb and GaSb layers repeating to form a superlattice structure; first and second p-type superlattice contact layers capping the absorber layer, each of the first and second layers having a wider bandgap than that of the absorber layer such that a heterostructure is formed between each of the first and second layers and the absorber layer. an n-type superlattice electrical contact layer on the first p-type superlattice contact layer which forms a n/p junction with the first p-type superlattice contact layers; a first contact on the n-type superlattice electrical contact layer; and a second contact on the second p-type superlattice contact layer.