Long‐wavelength InTlSb photodetectors operating at room temperature are reported. The photo‐ detectors were grown on (100) semi‐insulating GaAs substrates by low‐pressure metalorganic chemical vapor deposition. Photoresponse of InTlSb photodetectors is observed up to 11 &mgr;m at room temperature. The maximum responsivity of an In0.96Tl0.04Sb photodetector is about 6.64 V/W at 77 K, corresponding to a detectivity of about 7.64×108cm Hz1/2/W. The carrier lifetime in InTlSb photodetectors derived from the stationary photoconductivity is 10–50 ns at 77 K. ©1996 American Institute of Physics.