Narrow-gap semiconductor

Narrow-gap semiconductors are semiconducting materials with a magnitude of bandgap that is smaller than 0.5 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). Modern terahertz, infrared, and thermographic technologies are all based on this class of semiconductors.

Narrow-gap materials made it possible to realize satellite remote sensing, photonic integrated circuits for telecommunications,  and unmanned vehicle Li-Fi systems, in the regime of Infrared detector and infrared vision. They are also the materials basis for terahertz technology, including security surveillance of concealed weapon uncovering,  safe medical and industrial imaging with terahertz tomography,   as well as dielectric wakefield accelerators. 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. Space crafts, deep ocean instruments, and vacuum physics setups use narrow-gap semiconductors to achieve cryogenic cooling.

List of narrow-gap semiconductors

 * {| class="wikitable"

!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
 * Lead telluride
 * PbTe
 * IV-VI
 * 0.32 eV
 * Indium arsenide
 * InAs
 * III-V
 * 0.354 eV
 * Indium antimonide
 * InSb
 * III-V
 * 0.17 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
 * }
 * Tin selenide
 * SnSe
 * IV-VI
 * 0.9 eV
 * Silver(I) selenide
 * Ag2Se
 * 0.07 eV
 * Magnesium silicide
 * Mg2Si
 * II-IV
 * 0.79 eV
 * }
 * Mg2Si
 * II-IV
 * 0.79 eV
 * }