In this paper, we report on the growth of InSb on (100) Si and (111)B GaAs substrates and the growth of InAsSb alloys for longer wavelength applications. The fabrication and characterization of photodetectors based on these materials are also reported. Both photoconductive and photovoltaic devices are investigated. The photodiodes are InSb p-i-n structures and InSb/InAs 1-xSb x/InSb double heterostructures grown on (100) and (111)B semi-insulating GaAs and Si substrates by low pressure metalorganic chemical vapor deposition and solid source molecular beam epitaxy. The material parameters for device structures have been optimized through theoretical calculations based on fundamental mechanisms. InSb p-i-n photodiodes with peak responsivities approximately 10 3 V/W were grown on Si and (111) GaAs substrates. An InAsSb photovoltaic detector with a composition of x = 0.85 showed photoresponse up to 13 μm at 300 K with a peak responsivity of 9.13 × 10 -2 V/W at 8 μm. The R oA product of InAsSb detectors has been theoretically and experimentally analyzed.