The dependence of photoluminescence spectra and surface morphology on misfit strain are investigated for highly strained InxGa1−xSb/Al0.35Ga0.65Sb quantum wells grown on GaSb(001) by molecular beam epitaxy. Infrared photoluminescence with a wavelength as long as 1.95 &mgr;m is observed at room temperature from a multiple‐quantum well. The measured photoluminescence wavelength is in good agreement with that calculated by the theory in which strain effects are taken into account for a single‐strained quantum well condition. The photoluminescence intensity decreases remarkably when width of strained quantum well exceeds the critical layer thickness (CLT) that depends on the misfit, i.e., indium content of the well layer. The mechanical‐equilibrium theory of the generation of misfit dislocations predicts the CLT observed successfully. ©1995 American Institute of Physics.