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InSb has the appearance of dark-grey silvery metal pieces or powder with vitreous lustre. When subjected to temperatures over 500 °C, it melts and decomposes, liberating antimony and antimony oxide vapors.
InSb is a narrow-gap semiconductor with an energy band gap of 0.17 eV at 300 K and 0.23 eV at 80 K. The crystal structure is zincblende with a 0.648 nm lattice constant.
Undoped InSb possesses the largest ambient-temperature electron mobility (78000 cm2/(V*s)), electron drift velocity, and ballistic length (up to 0.7 μm at 300 K) of any known semiconductor, except possibly for carbon nanotubes.
Indium antimonide photodiode detectors are photovoltaic, generating electric current when subjected to infrared radiation. InSb's internal quantum efficiency is effectively 100% but is a function of the thickness particularly for near bandedge photons. Like all narrow bandgap materials InSb detectors require periodic recalibrations, increasing the complexity of the imaging system. This added complexity is worthwhile where extreme sensitivity is required, e.g. in long-range military thermal imaging systems. InSb detectors also require cooling, as they have to operate at cryogenic temperatures (typically 80 K). Large arrays (up to 2048x2048 pixels) are available. HgCdTe and PtSi are materials with similar use.
A layer of indium antimonide sandwiched between layers of aluminium indium antimonide can act as a quantum well. This approach is studied in order to construct very fast transistors. Bipolar transistors operating at frequencies up to 85 GHz were constructed from indium antimonide in the late 1990s; field-effect transistors operating at over 200 GHz have been reported more recently (Intel/QinetiQ). Some models suggest that terahertz frequencies are achievable with this material. Indium antimonide semiconductor devices are also capable of operating with voltages under 0.5 V, reducing their power requirements.
Indium Antimonide crystal