Direct detection thin-film bipolar narrow-gap Hg<sub>1-x</sub>Cd<sub>x</sub>Te semiconductor is considered as a waveguide THz/sub-THz bolometer. The response of such thin layer detectors was calculated and measured in ν=0.037-1.54 THz frequency range at T~70-300 K. Noise equivalent power of such detectors can reach NEP<sub>300K</sub>~4×10<sup>-10</sup> W/Hz<sup>1/2</sup> and NEP<sub>100K</sub>~10<sup>-11</sup> in sub-THz frequency range.
Direct detection mm/sub-mm wave warm-carrier bipolar narrow-gap Hg<sub>1-x</sub>Cd<sub>x</sub>Te semiconductor bolometers
that can be used as picture elements in THz sensitive arrays, are considered. The response of Hg<sub>1-x</sub>Cd<sub>x</sub>Te warm-electron
bolometers was measured in v=0.037-1.54 THz frequency range at T=68-300 K. Bipolar semiconductor warm-electron
bolometer theoretical model was developed. In the detector considered the electromagnetic wave propagates in
semiconductor waveguide, heats electrons and holes, creates their excess concentrations, as well as, the electromotive
forces. These effects cause the bolometer response voltage. Experimental results confirm the model main conclusions.
Because of response time defined by carrier recombination time in HgCdTe layers (τ~10-8-10-6 s) and the noise
equivalent power that can reach NEP<sub>300 K~</sub>4×10-10 W/Hz1/2 in mm-wave region, the arrays on the base of HgCdTe
bolometers can make them promising for active relatively fast frame rate sensitive applications. At liquid nitrogen
temperature NEP can lowering up to NEP<sub>77</sub> <sub>K~</sub>10-11 W/Hz<sup>1/2</sup>. Embeded p-n-junctions in HgCdTe can increase the
detectors responsivity by an order.
Narrow-gap direct detection mercury cadmium telluride (MCT) THz semiconductor hot electron bolometer (SHEB)
is considered. Device operation takes into account the phenomena in semiconductor bipolar plasma and hot-carrier
effect at uncooled or slightly cooled conditions. To examine the SHEB detector in the wide range of operation
frequencies (ν=0.037-1.58 THz) the simplest dipole antennas were used in prototype arrays.
The experiments were performed at <i>T</i> = 300 K at ν= 37, 50, 75 GHz, 0.89 and 1.58 THz with a MCT SHEB devices
with intrinsic conductivity. At ν=1.58, 0.89, 0.078 and 0.037 THz the signal temperature dependencies were measured
too. The sensitivity was S<sub>v</sub>~2.5 V/W (estimated NEP~4×10<sup>-10</sup> W/Hz<sup>1/2</sup>) at <i>T</i>=300 K; and S<sub>v</sub>~2×10<sup>3</sup> V/W (estimated
NEP~3×10<sup>-12</sup> W/Hz<sup>1/2</sup>) at <i>T</i>=78K and ν=37, and 78 GHz. The signal temperature dependences at ν=0.89 THz are
different compared to those at ν=37 and 78 GHz. Temperature phase dependent signals are discussed with their
dependence on energy relaxation time. A model of such a detector is developed. The radiation entrance through
semiconductor surface and metal contacts are both modeled.