We report a fully relaxed low threading dislocation density InSb layer grown on a GaAs substrate using self-assembled periodic interfacial misfit dislocations. The InSb layer was grown at 310 °C by molecular beam epitaxy. The AFM measurement exhibited a root mean square (r.m.s.) roughness of 1.1 nm. ω−2θ scan results from x-ray diffraction measurement indicated that the  InSb layer is 98.9% relaxed. Images from the transmission electron microscope measurement showed a threading dislocation density of 1.38×10⁸ cm⁻². The formation of highly uniform interfacial misfit dislocation array was also observed and the separation of dislocations is consistent with theoretical calculation. The InSb layer exhibited a 33,840 cm²/V s room temperature electron mobility.