Uncooled long wavelength infrared photon detectors

Abstract Infrared (IR) photon detectors operating in the middle (3–5 μm) and long wavelength (8–14 μm) infrared spectral range require cryogenic cooling to achieve useful performance. The need for cooling is a major limitation of IR photon detectors what prevents more widespread use of IR technology. At present, uncooled thermal detector focal plane arrays are successfully used in staring thermal imagers. However, the performance of thermal detectors is modest, they suffer from slow response and they are not very useful in applications requiring multispectral detection. In the paper, a number of concepts to improve performance of photon detectors operating at room temperature are presented. Several types of detector materials are considered: HgCdTe, Sb-based III–V ternary alloys, and type-II InAs/GaInSb superlattice. Initial efforts were concentrated on photoconductors and photoelectromagnetic detectors. Recently, advanced heterojunction photovoltaic detectors have been developed. It is shown that uncooled HgCdTe photovoltaic detector can achieve detectivity of 109 cm Hz1/2 W−1 at the 8–9 μm range. Potentially the devices can be assembled in large focal plane arrays. This will enable obtaining of NEDT of less than 0.1 K for staring thermal imagers operating with f/1 optics and 30 s−1 frame rate.