Indium antimonide

InSb infrared detector manufactured by Mullard in the 1960s.

InSb is a narrow direct band gap semiconductor with an energy band gap of 0.17 eV at 300 K and 0.23 eV at 80 K.[8]

Undoped InSb possesses the largest ambient-temperature electron mobility of 78000 cm²/(V⋅s),[9] electron drift velocity, and ballistic length (up to 0.7 μm at 300 K)[8] of any known semiconductor, except 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.[10] 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 2048×2048 pixels) are available.[11] 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. In such a heterostructure InSb/AlInSb has recently been shown to exhibit a robust quantum Hall effect.[12] This approach is studied in order to construct very fast transistors.[13] 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.