Latest achievements on MCT IR detectors for space and science imaging
2016
HgCdTe (MCT) is a very versatile material for IR detection. Indeed, the ability to tailor the cutoff frequency as close as
possible to the detection needs makes it a perfect candidate for high performance detection in a wide range of
applications and spectral ranges. Moreover, the high quality material available today, either by liquid phase epitaxy
(LPE) or molecular beam epitaxy (MBE) allows for very low dark currents at low temperatures and make it suitable for
very low flux detection application such as science imaging. MCT has also demonstrated its robustness to aggressive
space environment and faces therefore a large demand for space application such as staring at the outer space for science
purposes in which case, the detected photon number is very low This induces very strong constrains onto the detector:
low dark current, low noise, low persistence, (very) large focal plane arrays. The MCT diode structure adapted to fulfill
those requirements is naturally the p/n photodiode. Following the developments of this technology made at DEFIR and
transferred to Sofradir in MWIR and LWIR ranges for tactical applications, our laboratory has consequently investigated
its adaptation for ultra-low flux in different spectral bands, in collaboration with the CEA Astrophysics lab. Another
alternative for ultra low flux applications in SWIR range, has also been investigated with low excess noise MCT n/p
avalanche photodiodes (APD). Those APDs may in some cases open the gate to sub electron noise IR detection.. This
paper will review the latest achievements obtained on this matter at DEFIR (CEA-LETI and Sofradir common
laboratory) from the short wave (SWIR) band detection for classical astronomical needs, to the long wave (LWIR) band
for exoplanet transit spectroscopy, up to the very long waves (VLWIR) band.
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