Moderately cooled, fast and diffraction-limited THz bolometer is proposed and its theoretical model is
developed. Unlike thermal bolometers, the radiation rapidly heats only electrons in narrow gap bipolar
semiconductor without the semiconductor lattice inertial heating. In conditions determined this heating changes
generation and recombination processes, that leads to the carrier concentration decrease and semiconductor
resistance rise. This rise creates the device output signal. According to this model the SHEB on base of narrow gap
mercury cadmium telluride (MCT) semiconductor at temperature of T = 78 K can have detectivity D* ~ (0.3-2)107
cmHz1/2/W in the range of (0.01-1.5) THz.