The common believe was that infrared photodetectors of the mid and long wavelength infrared radiation need to be cooled to achieve a high sensitivity. Cooling  is a straightforward way to suppress thermal generation of charge carriers and reduce related noise. But, at the same time, cooling requirements make infrared systems bulky, heavy and inconvenient in use.

A number of concepts to improve performance of photodetectors operating at near room temperatures have been proposed. Recent considerations of the fundamental detector mechanisms suggest that near perfect detection can be achieved in the MWIR and LWIR range without the need for cryogenic cooling.

This paper, to a large degree, is based on the research, development and fabrication of uncooled HgCdTe detectors in Poland. The devices are based on 3D-variable band gap and doping level structures, that integrate optical, detection and electric functions in a monolithic chip. The architecture of the structures is optimized for the best compromise between requirements of a high quantum efficiency, efficient and fast collection of photogenerated charge carriers, minimized thermal generation, reduced parasitic impedances, wide linear range, wide acceptance angles and other device features.

Recent refinements in the devices design and technology have lead to sensitivities close to fundamental limits due to quantum noise of the background thermal radiation, extension of useful spectral range to >16 µm wavelength and picosecond range response times. The devices have found numerous applications in various optoelectronic systems.

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1. High Operation Temperature (HOT) photodetectors