InSb

Indium antimonide (InSb) is a III–V compound semiconductor formed from indium and antimony. It crystallizes in the zinc blende structure and has a direct, narrow bandgap of about 0.17 eV at room temperature, corresponding to infrared wavelengths up to roughly 7 micrometers. This small bandgap gives InSb strong infrared absorption and high intrinsic carrier concentrations at room temperature, supporting infrared detectors and low-noise, high-speed devices.

Electronic and optical properties are notable for very high electron mobility and a small electron effective mass. Electron mobility in InSb is among the highest for semiconductors (around 7.8 × 10^4 cm^2/(V·s) at room temperature), with an electron effective mass near 0.013 m0. These properties enable fast transistor operation and rapid photodetection. InSb exhibits a direct bandgap, allowing efficient interband absorption in the near to mid-infrared range, typically supporting detector response from about 1 to 7 μm depending on temperature and structure.

Growth and substrates form an important consideration. InSb crystals are grown by methods such as Bridgman–Stockbarger or Czochralski processes, and can be grown as epitaxial layers by liquid-phase epitaxy or molecular beam epitaxy. Substrates commonly used include GaSb, with buffer layers employed to accommodate lattice mismatches; the lattice constant is about 6.477 Å. On exposure to air, InSb surfaces readily oxidize and require passivation to maintain device performance.

Applications are dominated by infrared technologies. InSb is used in infrared imaging and spectroscopy detectors, especially in the short- to mid-wavelength infrared range, for thermal imaging and night-vision systems. It also finds use in high-speed electronics and heterostructures, where its large mobility can improve device speed and performance. Handling considerations include the toxicity of antimony compounds and the need for low-temperature processing to mitigate defects and dark current.