Two-Dimensional Long-Wavelength and Very Long-Wavelength Focal-Plane Arrays at AIM
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In recent years AIM has expanded its portfolio of standard infrared (IR) focal-plane arrays in the 3 μm to 5 μm (mid-wavelength infrared, MWIR) and 8 μm to 10 μm (long-wavelength infrared, LWIR) spectral ranges with two-dimensional IR detectors, sensitive in the 0.9 μm to 2.5 μm (short-wavelength infrared, SWIR) and especially in the 10 μm to 15 μm (very long-wavelength infrared, VLWIR) spectral ranges. This paper reports on the latest technological advancements that will benefit not only prototype applications for which they are demonstrated but a wide range of AIM products. A reduction of the pixel pitch from 24 μm to 15 μm is the result of increasing demands for compact detection modules with reduced weight, size, power consumption, and cost efficiency. Performance characterization for such a reduced-pitch 640 × 512 module in the LWIR (cut-off 10.5 μm at 67 K) yields mean noise equivalent temperature difference of 32.2 mK and defective pixel rate of only 0.5%. Extending the detection wavelength further into the VLWIR is of major interest for space applications such as the Meteosat Third Generation, which poses challenging requirements for sensor material homogeneity and dark-current density. To meet this requirement, an extrinsic doping approach is utilized on a 256 × 256 mercury cadmium telluride (MCT) focal-plane array with ∼14 μm cut-off wavelength at 55 K operating temperature, and a dark- current density of about 1 pA/μm2 is demonstrated.
KeywordsHgCdTe infrared detector liquid-phase epitaxy (LPE) small pixel very long-wavelength infrared (VLWIR) extrinsic doping dark current
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