Photodetectors based on diode heterostracture with InAsSbx photosensitive region (x = 0.38) with long-wave cut-off λ0.1 about 10 μm (296 K) are investigated. The dependences of dark current density and detectivity in the temperature range of 200–425 K have been investigated. It is shown that the experimental samples are characterized by values of dark current density about 500 A/cm2 at room temperature, detectivity 1.2 × 109 and 5 × 109 cm Hz1/2 W–1 at room temperature and 250 K, respectively, and diffusion mechanism of current flow in the temperature range 200–350 K.