InAs1_xSbx materials are of great importance due to their potential of replacing HgCdTe material for the fabrication of infrared sources and detectors operating at wavelength 8-12 μm spectral range where the atmospheric absorption is minimum. Heteroepitaxial layers of InAsi_xSbx materials have been successfully prepared by molecular beam epitaxy (MBE) over the complete compositional range (0<x<1) on (100)InAs substrates. Details of the MBE system and the growth have been described elsewhere.1,2 Photoluminescence has been employed to characterize the material quality and explore the possibility of applications in optical sources. Band-edge photoluminescence peak wavelengths as long as 8 pm have been obtained for the first time among III-V compound semiconductor materials in spite of the existence of a large lattice mismatch up to N6.4%. These results are indicative of high quality material.