Infrared Detectors
Tellurium-based compounds such as cadmium telluride (CdTe) and mercury cadmium telluride (HgCdTe) have been used as infrared (IR) detectors for over half a century. These versatile narrow gap semiconducting materials are characterized by a direct energy g
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Infrared Detectors Gurinder Kaur Ahluwalia and Ranjan Patro
Infrared detector applications
G.K. Ahluwalia, Ph.D. (*) Materials and Nanotechnology Research Laboratory, Department of Physics College of The North Atlantic, Labrador West Campus, 1600 Nichols Adam Highway, Labrador City, A2V 0B8, NL, Canada e-mail: [email protected] R. Patro, Ph.D. Physics Department, College of the North Atlantic, 219 Hamilton River Road, P.O. Box 1720 Station B, Happy Valley Goose Bay, A0P1E0, NL, Canada © Springer International Publishing Switzerland 2017 G.K. Ahluwalia (ed.), Applications of Chalcogenides: S, Se, and Te, DOI 10.1007/978-3-319-41190-3_11
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G.K. Ahluwalia and R. Patro
Left: Non-cooled type and TE-cooled type photoconductive MCT detector, continuous operation cutoff wavelength: 5.4 μm, Photoconductive element that decreases its resistance by input of infrared light: Right: 10 μm band infrared detector with high sensitivity and high-speed response. Courtesy: Hamamatsu Corporation
11.1
Introduction
Infrared photodetectors (IRPD) are devices that respond to incident photons with wavelengths in the infrared spectrum (~1–1000 μm). Applications of infrared detectors include a wide spectrum [1] such as military and security, scientific, earth resources, medical, industrial, automotive, and energy conservation. Traditionally, IR technologies were used for controlling functions and night vision problems by forming IR images from temperature and emissive differences (systems for recognition and surveillance, tank sight systems, anti-tank missiles, air–air missiles, etc.). Common peaceful applications using infrared detectors include rail safety, space operations, gas leak detection, flame detection, alcohol level testing, anesthesiology testing, petroleum exploration, temperature sensing, water and steel analysis. Infrared motion detectors are used in home alarm systems. Thermal night vision goggles collect infrared radiation particles by sensing the emitted heat and using these particles in order to create a picture. IR detectors assist night driving, night flying and night surveillance, wildlife observation, and search and rescue missions. Law enforcement officials can also use IR detectors to help them find criminals that may be hiding in dark areas. In general, all objects emit an IR spectrum based on their temperature. This emission spectrum can be approximated by wavelength, λ, as blackbody radiation, which can be characterized according to the blackbody’s temperature, T, by Eq. (11.1) [2, 3]: eB ðλ; T Þ dλ ¼
2πhc2 dλ λ ½ehc=λkT 1 5
ð11:1Þ
It implies that an object at room temperature will emit IR radiation with a peak intensity of around 9.5 μm, with detectable IR emissions for wavelengths microns away from this center value. While not every portion of the IR spectrum is
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ordinarily present due to natural blackbody radiation (a blackbody would need to be at a temperature of over 4000 K to have peak light emissions at the edge of the visible spectrum), these sources
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