For nearly 40 years AIM develops, manufactures and delivers photo-voltaic and photo-conductive infrared sensors and associated cryogenic coolers which are mainly used for military applications like pilotage, weapon sights, UAVs or vehicle platforms. In 2005 AIM started to provide the competences also for space applications like IR detector units for the SLSTR instrument on board of the Sentinel 3 satellite, the hyperspectral SWIR Imager for EnMAP or pushbroom detectors for high resolution Earth observation satellites. Meanwhile AIM delivered more than 25 Flight Models for several customers. The first European pulse-tube cooler ever operating on-board of a satellite is made by AIM. AIM homes the required infrared core capabilities such as design and manufacturing of focal plane assemblies, detector housing technologies, development and manufacturing of cryocoolers and also data processing for thermal IR cameras under one roof which enables high flexibility to react to customer needs and assures economical solutions. Cryogenically cooled Hg(1-x)CdxTe (MCT) quantum detectors are unequalled for applications requiring high imaging as well as high radiometric performance in the infrared spectral range. Compared with other technologies, they provide several advantages, such as the highest quantum efficiency, lower power dissipation compared to photoconductive devices and fast response times, hence outperforming micro-bolometer arrays. However, achieving an excellent MCT detector performance at long (LWIR) and very long (VLWIR) infrared wavelengths is challenging due to the exponential increase in the thermally generated photodiode dark current with increasing cut-off wavelength and / or operating temperature. Dark current is a critical design driver, especially for LWIR / VLWIR multi-spectral imagers with moderate signal levels or hyper-spectral Fourier spectrometers operating deep into the VLWIR spectral region. Consequently, low dark current (LDC) technologies are the prerequisite for future scientific space and earth observation missions. Aiming, for example at exoplanet or earth atmospheric spectral analysis, significant improvement in LWIR / VLWIR detector material performance is mandatory. LDC material optimization can target different directions of impact: (i) reduction of dark current for a given operational temperature to increase SNR and reduce thermally induced signal offset variations. (ii) operation at elevated temperatures at a given dark current level to reduce mass and power budget of the required cryocooler and to reduce cryostat complexity. (iii) increase the accessible cut-off wavelength at constant detector temperature and dark current level. This paper presents AIM’s latest results on n-on-p as well as p-on-n low dark current planar MCT photodiode focal plane detector arrays at cut-off wavelengths >11 μm at 80 K. Dark current densities below Tennant’s ‘Rule07’1 have been demonstrated for n-on-p and p-on-n devices. This work has been carried out under ESA contract ESTEC 4000107414/13/NL/SFe².
In the framework of this paper, AIM presents the actual status of some of its currently ongoing focal plane detector
module developments for space applications covering the spectral range from the short-wavelength infrared (SWIR) to
the long-wavelength infrared (LWIR) and very-long-wavelength infrared (VLWIR), where both imaging and
spectroscopy applications will be addressed. In particular, the integrated detector cooler assemblies for a mid-wavelength
infrared (MWIR) push-broom imaging satellite mission, for the German hyperspectral satellite mission EnMAP will be
elaborated. Additionally dedicated detector modules for LWIR/VLWIR sounding, providing the possibility to have two
different PVs driven by one ROIC will be addressed.
In the framework of this paper, AIM presents the actual status of some of its currently ongoing focal plane detector
module developments for space applications covering the spectral range from the short-wavelength infrared (SWIR) to the long-wavelength infrared (LWIR) and very-long-wavelength infrared (VLWIR), where both imaging and spectroscopy applications will be addressed. In particular, the integrated detector cooler assemblies for a mid-wavelength infrared (MWIR) push-broom imaging satellite mission, for the German hyperspectral satellite mission EnMAP will be elaborated. Additionally dedicated detector modules for LWIR/VLWIR sounding, providing the possibility to have two different PVs driven by one ROIC will be addressed.
Next generation infrared sensor space applications are based on technological evolutions on many frontiers. Sensor
material improvements and device developments are two of them. This presentation reports on the latest results on
HgCdTe (MCT) very long wavelength infrared (VLWIR) photovoltaic (PV) sensors and on the development of short
wavelength infrared (SWIR) avalanche photodiodes (APDs).
The dark current of photodiodes increases exponentially with increasing cut-off wavelength. To keep the dark current at
an acceptable level, operational temperatures of MCT PV sensors with photo-sensitivity above 12 μm wavelength are
typically around 50 K. Therefore, until recently, VLWIR MCT detectors have been built with photoconductive (PC)
linear arrays or small 2D arrays enabling the higher operational temperatures of PC sensors (80 K - 120 K). The increasing
interest in VLWIR imaging spectrometers requires larger 2D arrays excluding PC technology. One approach for
feasible PV arrays is a significant reduction of the dark current by using extrinsically doped (in contrast to vacancy
doped) p-MCT material. This allows for enhanced performance at convenient temperatures of 50 - 55 K. Alternatively,
standard performance at higher operational temperatures at 60 K - 70 K is possible. AIM presents the latest results on its
extrinsically p-doped VLWIR MCT photodiodes with a 15 μm cut-off wavelength.
At the other side of the IR spectrum, AIM has a strong focus on focal plane arrays for low-photon flux SWIR applications.
For some applications, the sensitivity of SWIR arrays with capacitive transimpedance amplifier input stages is not
sufficient and APDs are required. AIM presents the latest results on its SWIR APD devices.
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