Advanced characterization of the radiometric performances of quantum well infrared photodetectors

This paper presents two test benches which were specifically developed at ONERA (French national aerospace research center) for advanced characterizations of infrared photodetectors. The first test bench relies on a Fourier Transform infrared spectrometer and delivers hyperspectral cartographies on a large spectral range (from 1.3 to 20 μm), with a rather good resolution (better than 16 cm−1). Hyperspectral cartographies of a 640 × 512 QWIP FPA prototype operating in the 8- to 10-μm spectral range are presented. Our measurements, coupled with an empirical model, allow one to extract technological parameters such as the pixels thickness or the mismatch between grating period and pixel pitch. The second test bench is dedicated to angular response measurements. The photodetector is illuminated with a blackbody with a varying angle of incidence θ. The originality of this experimental setup lies in the fact that both the detector and the blackbody are located in the same, large cryogenic assembly. Thus, the angle of incidence on the detector can be adjusted over a wide range (−80° to +80°), and measurements are performed with low background and low stray light. We present angular responses obtained on “low-noise QWIP” single elements with different etch depth of the grating and interpret them thanks to an intuitive model of grating coupling.