A CdZnTe/MgCdTe double-heterostructure (DH) consisting of a 3 μm thick Cd_0.9946 Zn_0.0054Te middle layer that is lattice-matched to an InSb substrate has been grown using molecular beam epitaxy. A long carrier lifetime of 3.4 × 10² ns has been demonstrated at room temperature, which is approximately three times as long as that of a CdTe/MgCdTe DH with identical layer thickness. This substantial improvement is due to the reduction in misfit dislocation density in the CdZnTe alloy. In contrast, a CdTe/MgCdTe DH with 3 μm thick CdTe layer grown on an InSb substrate exhibits a strain relaxation of ∼30%, which leads to a wider x-ray diffraction peak, a weaker integrated photoluminescence intensity, and a shorter minority carrier lifetime of 1.0 × 10² ns. These findings indicate that CdZnTe lattice-matched to InSb has great potential as applied to high-efficiency solar cells as well as virtual substrates for high-performance large-area HgCdTe focal plane arrays.