Narrow-gap semiconductors are semiconducting materials with a magnitude of bandgap that is smaller than 0.7 eV, which corresponds to an infrared absorption cut-off wavelength over 2.5 micron. A more extended definition includes all semiconductors with bandgaps smaller than silicon (1.1 eV). [1] [2] Modern terahertz, [3] infrared, [4] and thermographic [5] technologies are all based on this class of semiconductors.
Narrow-gap materials made it possible to realize satellite remote sensing, [6] photonic integrated circuits for telecommunications, [7] [8] [9] and unmanned vehicle Li-Fi systems, [10] in the regime of Infrared detector and thermography. [11] [12] They are also the materials basis for terahertz technology, including security surveillance of concealed weapon uncovering, [13] [14] [15] safe medical and industrial imaging with terahertz tomography, [16] [17] [18] as well as dielectric wakefield accelerators. [19] [20] [21] Besides, thermophotovoltaics embedded with narrow-gap semiconductors can potentially use the traditionally wasted portion of solar energy that takes up ~49% of the sun light spectrum. [22] [23] Spacecraft, deep ocean instruments, and vacuum physics setups use narrow-gap semiconductors to achieve cryogenic cooling. [24] [25]
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Name | Chemical formula | Groups | Band gap (300 K) |
---|---|---|---|
Mercury cadmium telluride | Hg1−xCdxTe | II-VI | 0 to 1.5 eV |
Mercury zinc telluride | Hg1−xZnxTe | II-VI | 0.15 to 2.25 eV |
Lead selenide | PbSe | IV-VI | 0.27 eV |
Lead(II) sulfide | PbS | IV-VI | 0.37 eV |
Tellurium | Te | VI | ~0.3 eV |
Lead telluride | PbTe | IV-VI | 0.32 eV |
Magnetite | Fe3O4 | Transition Metal-VI | 0.14 eV |
Indium arsenide | InAs | III-V | 0.354 eV |
Indium antimonide | InSb | III-V | 0.17 eV |
Germanium | Ge | IV | 0.67 eV |
Gallium antimonide | GaSb | III-V | 0.67 eV |
Cadmium arsenide | Cd3As2 | II-V | 0.5 to 0.6 eV |
Bismuth telluride | Bi2Te3 | 0.21 eV | |
Tin telluride | SnTe | IV-VI | 0.18 eV |
Tin selenide | SnSe | IV-VI | 0.9 eV |
Silver(I) selenide | Ag2Se | 0.07 eV | |
Magnesium silicide | Mg2Si | II-IV | 0.79 eV [26] |