In the middle and late 1950s, it was discovered that InSb had the smallest energy gap of any semiconductor known at that time, and its applications as a mid-wavelength infrared detector became obvious. The energy gap of InSb is less well matched to the 3- to 5-mm band at higher operating temperatures, and better performance can be obtained from Hg1 xCdxTe. InAs is a similar compound to InSb but has a larger energy gap such that the threshold wavelength is 3–4 mm.
Indium antimonide detectors have been extensively used in high-quality detection systems and have found numerous applications in the defense and space industry for more than 50 years. One of the best known (and most successful) of these systems is the Sidewinder™ air-to-air anti-aircraft missile. The most significant recent advance in infrared technology has been the development of large 2D FPAs for use in staring arrays. Array formats are available with readouts suitable for both high-background F/2 operation and low-background astronomy applications. L3 Cincinnati Electronics fabricates InSb sensors of 16 Mp (4096 x 4096 pixels) currently in use by U.S. assets in
overseas combat zones.
GaSb-related ternary and quaternary alloys are also established as materials for developing MWIR photodiodes for near-room-temperature operation and for the next generation of very low-loss fiber communication systems. Their current status is presented in Krier’s monograph.
The photoelectrical properties of narrow-gap photodiodes have been studied extensively; more details can be found in Refs. 5 and 6, especially Rogalski’s monograph, published in 2011, which covers the comprehensive range of subjects necessary to understand infrared detector theory and technology. Here we emphasize our consideration of achievements made in the last two decades.
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