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We demonstrate the suppression of the bulk generationrecombination current in nBn devices based on an InAsSb active layer (AL) and a AlSbAs barrier layer (BL). This leads to much lower dark currents than in conventional InAsSb photodiodes operating at the same temperature. When the BL is p-type, very high doping must be used in the AL (nB p n +). This results in a significant shortening of the device cutoff wavelength due to the Moss-Burstein effect. For an n-type BL, low AL doping can be used (nB n n), yielding a cutoff wavelength of ∼4.1 μm and a dark current close to ∼3 × 10 − 7 A/cm 2 at 150 K. Such a device with a 4-μm-thick AL will exhibit a quantum efficiency (QE) of 70% and background-limited performance operation up to 160 K at f/3. We have made nB n n focal plane array detectors (FPAs) with a 320 × 256 format and a 1.3-μm-thick AL. These FPAs have a 35% QE and a noise equivalent temperature difference of 16 mK at 150 K and f/3. The high performance of our nB n n detectors is closely related to the high quality of the molecular beam epitaxy grown InAsSb AL material. On the basis of the temperature dependence of the diffusion limited dark current, we estimate a minority carrier lifetime of ∼670 ns. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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