The optical properties of InAsSb, nominally lattice marched to GaSb, grown at varying substrate temperatures with and without Bi-surfactant exposure, were studied with photoluminescence (PL). Both Bi exposure and increasing substrate temperatures reduce the Sb-incorporation and produce strained layers. The bandgap of lattice mismatched layers grown in this way is lowered compared to unstrained material. The PL intensity decreases dramatically when the lattice mismatch increases. The PL intensity also shows significant broadening that can be interpreted as evidence for inhomogeneous alloy distributions induced by the Bi. Published by Elsevier EN.