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High-resolution QWIP focal plane arrays: Towards third-generation thermal imagers

Hochauflösende QWIP Bildfeldmosaike: Wärmebildgeräte der dritten Generation
: Schneider, H.; Fleißner, J.; Maier, T.; Walther, M.; Koidl, P.; Weimann, G.; Cabanski, W.; Finck, M.; Menger, P.; Rode, W.; Ziegler, J.

Sixth Joint International Military Sensing Symposium, MSS 2004. Proceedings. CD-ROM
Dresden, 2004
International Military Sensing Symposium (MSS) <6, 2004, Dresden>
Conference Paper
Fraunhofer IAF ()
GaAs/AlGaAs; Qwip; dual-band; FPA; focal plane array; Bildfeldmosaik

GaAs-based quantum well infrared photodetector (QWIP) focal plane arrays (FPA) have developed into an important class of infrared sensors for thermal imaging. Mature III-V technology enables us to realize large infrared detector arrays with excellent thermal and spatial resolution, low fixed-pattern noise, and low 1/f noise at moderate cost. A high pixel operability of typically 99.9% without cluster defects makes QWIP FPAs ideally suited for many applications. In this work, we will report on our QWIP FPA developments for the 8 - 12 µm long-wavelength infrared (LWIR) and 3 - 5 µm mid-wavelength infrared (MWIR) spectral bands and on a new MWIR/LWIR dual-band FPA with pixel-registered simultaneous integration. In the LWIR, we have used several device concepts, giving rise to photoconductive and photovoltaic operation, to build QWIP FPAs with array sizes from 256x256 to 640x512 pixels. The FPAs achieve excellent thermal resolution, with a noise-equivalent temperature difference (NETD) down to 5 mK. We have also realized a 640x512 MWIR FPA based on strained InGaAs/AlGaAs QWIPs with 14 mK NETD at a detector temperature of 88 K. We have recently realized a dual-band MWIR/LWIR QWIP FPA with 384x288 pixels and simultaneous integration in both spectral bands on each pixel. The FPA comprises a photovoltaic and photoconductive QWIP for the LWIR and MWIR, respectively, and exhibits 17 mK and 43 mK NETD (7.6 ms, f/2 aperture). For dual-band FPAs, QWIP technology has the unique property that the active region for LWIR detection does not absorb MWIR radiation. This behavior makes the distinction between the two bands much easier than in the case of HgCdTe or any other detector material based on interband transitions.