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QWIP FPAs for high-performance thermal imaging

QWIP FPAs für hochwertige Wärmebildtechnik
: Schneider, H.; Walther, M.; Schönbein, C.; Rehm, R.; Fleißner, J.; Pletschen, W.; Braunstein, J.; Koidl, P.; Weimann, G.; Ziegler, J.; Cabanski, W.


Physica. E 7 (2000), No.1/2, pp.101-107
ISSN: 1386-9477
Journal Article
Fraunhofer IAF ()
QWIP camera; QWIP Kamera; focal plane array; Bildfeldmatrix; noise-equivalent temperature difference; Rausch-äquivalente Temperaturdifferenz; GaAs/AlGaAs

System properties of focal plane array (FPA) cameras based on GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) operating in the long-wavelength infrared are analyzed. Due to the limited charge storage capacity of available readout circuits, a small photoconductive gain improves the noise-equivalent temperature difference (NE delta T) of the sensor. We have demonstrated several camera systems based on conventional photoconductive QWIPs with NE delta T < 10 mK and NE delta T < 20 mK for FPAs with 256 x 256 and 640 x 512 pixels, respectively. A small photoconductive gain is obtained by operating the QWIP at very small electric fields (< 3 kV/cm). Finally, we discuss the possibility of reducing the NE delta T even further by using QWIP structures in which the photoexcited carrier mean free path is controlled by the incorporation of additional epitaxial layers. We thus obtain a high detectivity at very small signal and noise currents, which is useful in particular for large arrays with reduced pixel sizes. In addition, these detectors are shot-noise limited since the recombination noise is suppressed. The performance of FPA sensors based on these detectors will be addressed.