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Low-noise QWIPs for FPA sensors with high thermal resolution

Rauscharme QWIPs für Bildfeldmosaikdetektoren hoher thermischer Auflösung
: Schneider, H.; Walther, M.; Fleissner, J.; Rehm, R.; Diwo, E.; Schwarz, K.; Koidl, P.; Weimann, G.


Andresen, B.F. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Infrared Technology and Applications XXVI : 30 July - 3 August 2000, San Diego, USA
Bellingham/Wash.: SPIE, 2000 (SPIE Proceedings Series 4130)
ISBN: 0-8194-3775-1
Conference on Infrared Technology and Applications <26, 2000, San Diego/Calif.>
Conference Paper
Fraunhofer IAF ()
QWIP camera; QWIP Kamera; focal plane array; Bildfeldmosaik; thermal imaging; Wärmebildkamera; noise-equivalent temperature difference; Rausch-äquivalente Temperaturdifferenz; NETD; detectivity; Detektivität

We report on novel low-noise QWIP focal plane arrays (FPAs) which allow us to improve the thermal resolution of infrared sensors in the long-wavelength infrared (LWIR) atmospheric window. Our concept uses detector structures with a small photoconductive gain in order to achieve simultaneously a high internal quantum efficiency and a small responsivity. In comparison to conventional QWIPs where each period consists of a quantum well and a thermionic barrier, our approach involves additionally a combination of a narrow quantum well and a tunnel barrier. Due to these additional layers, a high emission probability of the photoexcited carriers and an efficient capture into the ground subband of the subsequent period are simultaneously achieved. FPA cameras using these detectors show an extremely low noise-equivalent temperature difference (NEdeltaT) and a high dynamic range. In particular, NEdeltaTs of only 7.2 mK and 5.2 mK (at 20 ms and 40 ms integration time, respectively) are observed for a 256x256 FPA camera system which we have realized using low-noise QWIPs. This value is the best temperature resolution ever obtained for thermal imagers operating in the LWIR.