Issues associated with the development and exploitation of infrared (IR) and terahertz (THz) radiation detectors based on a narrow-gap “HgCdTe” semiconductor have been discussed. This mercury–cadmium–telluride (MCT) semiconductor can be applied for two-color detector operation in IR and sub-THz spectral ranges. Two-color uncooled and cooled down to 78 K narrow-gap MCT semiconductor thin layers grown using the liquid phase epitaxy or molecular beam epitaxy methods on high-resistive “CdZnTe” or “GaAs” substrates, with bow-type antennas, have been considered both as sub-THz direct detection bolometers and 3 to 10 μm IR photoconductors. Their room temperature noise equivalent power at the frequency ν≈140 GHz and signal-to-noise ratio at the spectral sensitivity maximum under monochromatic (spectral resolution ∼0.1 μm) globar illumination reached the following values; ∼4.5×10−10 W/Hz1/2 and ∼50, respectively. Aspheric lenses used for obtaining the images in the sub-THz spectral region were designed and manufactured. With these detectors, about 140 and 270 GHz imaging data have been demonstrated.
Development of infrared and sub-terahertz radiation detectors at the same sensitive elements on the base of mercurycadmium- telluride (MCT) is reported. Two-color un-cooled and cooled to 78 K narrow-gap MCT semiconductor thin layers, grown by liquid phase epitaxy or molecular beam epitaxy method on high resistivity CdZnTe or GaAs substrates, with bow-type antennas were considered both as sub-terahertz direct detection bolometers and 3 to 10 μm infrared photoconductors. Their room temperature noise equivalent power (NEP) at frequency ~ 140 GHz and signal-to-noise ratio (S/N) in the spectral sensitivity maximum under the monochromatic (spectral resolution of ~0.1 μm) globar illumination were reached NEP ~4.5*10-10 W/Hz1/2 and S/N~50, respectively.
Direct detection thin-film bipolar narrow-gap Hg1-xCdxTe 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 NEP300K~4×10-10 W/Hz1/2 and NEP100K~10-11 in sub-THz frequency range.
Direct detection mm/sub-mm wave warm-carrier bipolar narrow-gap Hg1-xCdxTe semiconductor bolometers
that can be used as picture elements in THz sensitive arrays, are considered. The response of Hg1-xCdxTe 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 NEP300 K~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 NEP77K~10-11 W/Hz1/2. Embeded p-n-junctions in HgCdTe can increase the
detectors responsivity by an order.
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