To push HOT-performance, AIMs existing n-on-p technology has been improved by introducing Gold as an acceptor and reducing its concentration to the lower 1015/cm3 range as well as by optimizing the passivation process. This results in a substantial reduction in dark current density, a prerequisite for HOT operation. Recent dark current data are compared to ones previously obtained as well as to Tennant`s Rule07 , a generally accepted bench mark in this context.
Furthermore, we present electro-optical parameters obtained in the temperature range from 120 K to 170 K on resulting FPAs with 640x512 pixels, a pitch of 15 μm and a typical (80 K) cutoff wavelength of 5.1 μm.
Size, weight and power (SWaP) reduction is highly desired by applications such as sights for the dismounted soldier or small gimbals for UAVs. But why have high performance and small size of IR systems inevitably exclude each other? Namely, recent development progress in the fields of miniature cryocoolers, short dewars and high operating temperature (HOT) FPAs combined with pitch size reduction opens the door for very compact MWIR-modules while keeping high electro-optical performance.
Now, AIM has realized first prototypes of an ultra-compact high-performance MWIR engine in a total volume of only 18cl (60mm length x 60mm height x 50mm width). Impressive SWaP characteristics are completed by a total weight below 400g and a power consumption < 4W in basic imaging mode. The engine consists of a XGA-format (1024x768) MCT detector array with 10μm pitch and a low power consuming ROIC. It is cooled down to a typical operating temperature of ~160K by the miniature linear cryocooler SX020. The dewar uses a short coldfinger and is designed to reduce the heat load as much as possible. The cooler drive electronics is implemented in the CCE layout in order to reduce the required space of the printed boards and to save power. Uncorrected 14bit video data is provided via Camera Link. Optionally, a small image processing board can be stacked on top of the CCE to gain access to basic functions such as BPR, 2- point NUC and dynamic reduction. This paper will present the design, functionalities and performance data of the ultra-compact MCT MWIR engine operated at HOT.
For SWIR imaging applications, based on AIM’s state-of-the-art MCT IR technology specific detector designs for either low light level imaging or laser illuminated active imaging are under development. For imaging under low-light conditions a low-noise 640x512 15μm pitch ROIC with CTIA input stages and correlated double sampling was designed. The ROIC provides rolling shutter and snapshot integration. To reduce size, weight, power and cost (SWaP-C) a 640x512 format detector in a 10μm pitch is been realized. While LPE grown MCT FPAs with extended 2.5μm cut-off have been fabricated and integrated also MBE grown MCT on GaAs is considered for future production. The module makes use of the extended SWIR (eSWIR) spectral cut-off up to 2.5μm to allow combination of emissive and reflective imaging by already detecting thermal radiation in the eSWIR band. A demonstrator imager was built to allow field testing of this concept. A resulting product will be a small, compact clip-on weapon sight. For active imaging a detector module was designed providing gating capability. SWIR MCT avalanche photodiodes have been implemented and characterized on FPA level in a 640x512 15μm pitch format. The specific ROIC provides also the necessary functions for range gate control and triggering by the laser illumination. The FPAs are integrated in a compact dewar cooler configuration using AIM’s split linear cooler. A command and control electronics (CCE) provides supply voltages, biasing, clocks, control and video digitization for easy system interfacing. First lab and field tests of a gated viewing demonstrator have been carried out and the module has been further improved.
AIM has developed SWIR modules including FPAs based on liquid phase epitaxy (LPE) grown MCT usable in a wide range of hyperspectral imaging applications. Silicon read-out integrated circuits (ROIC) provide various integration and readout modes including specific functions for spectral imaging applications. An important advantage of MCT based detectors is the tunable band gap. The spectral sensitivity of MCT detectors can be engineered to cover the extended SWIR spectral region up to 2.5μm without compromising in performance. AIM developed the technology to extend the spectral sensitivity of its SWIR modules also into the VIS. This has been successfully demonstrated for 384x288 and 1024x256 FPAs with 24μm pitch. Results are presented in this paper. The FPAs are integrated into compact dewar cooler configurations using different types of coolers, like rotary coolers, AIM’s long life split linear cooler MCC030 or extreme long life SF100 Pulse Tube cooler. The SWIR modules include command and control electronics (CCE) which allow easy interfacing using a digital standard interface. The development status and performance results of AIM’s latest MCT SWIR modules suitable for hyperspectral systems and applications will be presented.
Based on AIM’s state-of-the-art MCT IR technology, detector modules for the SWIR spectral range have been
developed, fabricated and characterized. While LPE grown MCT FPAs with extended 2.5μm cut-off have been
fabricated and integrated also MBE grown MCT on GaAs is considered for future production.
Two imaging applications have been in focus operating either in passive mode by making use of e.g. the night glow, or
in active mode by laser illumination for gated viewing. Dedicated readout integrated circuits (ROIC), realized in
0.18μm Si-CMOS technology providing the required functionality for passive imaging and gated imaging, have been
designed and implemented. For both designs a 640x512 15μm pitch format was chosen. The FPAs are integrated in
compact dewar cooler configurations using AIM’s split linear coolers. A command and control electronics (CCE)
provides supply voltages, biasing, clocks, control and video digitization for easy system interfacing.
For imaging under low-light conditions a low-noise 640x512 15μm pitch ROIC with CTIA input stages and correlated
double sampling was designed. The ROIC provides rolling shutter and snapshot integration. To reduce size, weight,
power and cost (SWaP-C) a 640x512 format detector in a 10μm pitch is under development. The module makes use of
the extended SWIR spectral cut-off up to 2.5μm.
To be used for active gated-viewing operation SWIR MCT avalanche photodiodes have been implemented and
characterized on FPA level in a 640x512 15μm pitch format. The specific ROIC provides also the necessary functions
for range gate control and triggering by the laser illumination. First lab and field tests of a gated viewing demonstrator
have been carried out.
The paper will present the development status and performance results of AIM’s MCT based SWIR Modules for
It is only some years ago, since VGA format detectors in 15μm pitch, manufactured with AIM’s MCT n-on-p LPE
standard technology, have been introduced to replace TV/4 format detector arrays as a system upgrade.
In recent years a rapid increase in the demand for higher resolution, while preserving high thermal resolution,
compactness and low power budget is observed. To satisfy these needs AIM has realized first prototypes of MWIR XGA
format (1024x768) detector arrays in 10μm pitch. They fit in the same compact dewar as 640x512, 15μm pitch detector
arrays. Therefore, they are best suited for system upgrade purposes to benefit from higher spatial resolution and keep
cost on system level low.
By combining pitch size reduction with recent development progress in the fields of miniature cryocoolers, short dewars
and high operating temperatures the way ahead to ultra-compact high performance MWIR-modules is prepared.
For cost reduction MBE grown MCT on commercially available GaAs substrates is introduced at AIM. Recently,
640x512, 15μm pitch FPAs, grown with MBE have successfully passed long-term high temperature storage tests as a
crucial step towards serial production readiness level for use in future products.
Pitch size reduction is not limited to arrays sensitive in the MWIR, but is of great interest for high performance LWIR or
3rd Gen solutions. Some applications such as rotorcraft pilotage require superior spatial resolution in a compact design to
master severe weather conditions or degraded visual environment such as brown-out. For these applications AIM is
developing both LWIR as well as dual band detector arrays in HD-format (1280x720) with 12μm pitch.
This paper will present latest results in the development of detector arrays with small pitch sizes of 10μm and 12μm at
AIM, together with their usage to realize compact cooled IR-modules.
Thermal imagers based on cooled LWIR Modules are the choice for many Army applications in battlefield conditions like e.g. Gunner and Commander Sights in armored vehicles or Pilotage and Targeting Sights for helicopters. AIM has developed and produces LWIR FPAs based on liquid phase epitaxy (LPE) grown MCT on in-house grown CdZnTe substrates with different formats up to detector arrays with 1280x1024 elements in a 15μm pitch. LWIR detector arrays with different spectral cut-off wavelengths in the range of 9μm up to >12μm have been produced and characterized. For cost reduction a fabrication of molecular beam epitaxy (MBE) grown MCT on GaAs substrates is developed.
Critical performance parameters of the detector arrays are temporal noise at low frequencies and the residual fixed pattern noise after non-uniformity correction. A performance-limiting factor of a LWIR FPA is also the available full well capacity (FWC) of the readout integrated circuit (ROIC) for signal integration. AIM has done a redesign of the standard 640x512, 15μm pitch ROIC using now 0.18μm Si-CMOS technology. The available FWC for signal integration could be significantly increased resulting in better NETD performance.
Further developments are done for pitch reduction to realize LWIR modules also with 12μm and 10μm pixel pitch. The FPAs are integrated in compact dewar cooler configurations using different kinds of cooler types, like AIM’s split linear coolers SX095 or SX040 or rotary integral types depending whatever fits best to the application. The paper will present the development status and performance results of AIM’s latest improved MCT LWIR Modules.
In today’s typical military operations situational awareness is a key element for mission success. In contrast to what is known from conventional warfare with typical targets such as tanks, asymmetric scenarios now dominate military operations. These scenarios require improved identification capabilities, for example the assessment of threat levels posed by personnel targets. Also, it is vital to identify and reliably distinguish between combatants, non-combatants and friendly forces. To satisfy these requirements, high-definition (HD) large format systems are well suited due to their high spatial and thermal resolution combined with high contrast. Typical applications are sights for long-range surveillance, targeting and reconnaissance platforms as well as rotorcraft pilotage sight systems. In 2012 AIM presented first prototypes of large format detectors with 1280 × 1024 elements in a 15μm pitch for both spectral bands MWIR and LWIR. The modular design allows integration of different cooler types, like AIM’s split linear coolers SX095 or SX040 or rotary integral types depending whatever fits best to the application. Large format FPAs have been fabricated using liquid phase epitaxy (LPE) or molecular beam epitaxy (MBE) grown MCT. To offer high resolution in a more compact configuration AIM started the development of a 1024 × 768 10μm pitch IRmodule. Keeping electro/optical performance is achieved by a higher specific charge handling capacity of the readout integrated circuit (ROIC) in a 0.18μm Si CMOS technology. The FPA size fits to a dewar cooler configuration used for 640 × 512 15μm pitch modules.
Detectors for the short-wave infrared (SWIR) spectral range are particularly suitable for observation under hazy weather conditions as well as under twilight or moon light conditions. In addition, SWIR detectors allow using the airglow for observation under moonless sky. SWIR detectors are commonly based on InGaAs or HgCdTe (MCT) and demand extremely low dark currents to ensure a high signal-to-noise ratio under low background light conditions. AIM has developed a read-out integrated circuit (ROIC) with 640×512 pixels and a 15 μm pixel pitch for low light level applications. The ROIC supports analog or digital correlated double sampling (CDS) for the reduction of reset-noise (also known as kTC-noise). Along with CDS, a rolling shutter (RS) mode has been implemented. The input stage of the ROIC is based on a capacitive transimpedance amplifier (CTIA) with two selectable gain settings. The dark current of our SWIR MCT detectors has recently been significantly reduced to allow for high operating temperatures. In contrast to InGaAs, the MCT material offers the unique possibility to adjust the cut-off wavelength according to the application while maintaining the matching of the lattice constant to the one of the CdZnTe substrate. The key electro-optical performance parameters of lately developed MCT based SWIR Focal Plane Arrays (FPA) with a 1.75 μm cut-off wavelength will be presented. In addition, AIMs SWIR detectors covering the spectral range from 0.9 μm to 2.5 μm and available in formats of 384×288 pixels - 24 μm pitch and 1024×256 pixels - 24×32 μm2, will be introduced.
Based on its well established 640×512 pixel, 15 µm pitch detector for a staring application, which is produced at AIM in high quantities at reproducible high yield and with superior performance, AIM has developed an MWIR and LWIR 1280×1024 pixel design with a 15 µm pixel pitch to make use of the advantages of large format detectors for IR systems applications. Benefitting from the continuous advancement of traditional liquid phase epitaxy (LPE) n-on-p technology, excellent electro-optical performance over a wide range of operating temperatures as well as enhanced long-term and thermal cycle stability have been achieved for this new and challenging detector format. In parallel, the performance of MCT material grown by molecular beam epitaxy (MBE), which is currently under development to take advantage of 3rd generation device architecture and the alternative GaAs substrate material, is evaluated for this application. In this paper, we will present the results of electro-optical detector characterizations and IR images of MWIR and LWIR 1280×1024 FPAs fabricated by LPE. We demonstrate the progress in MBE development at AIM and present electro-optical figures of merit, e.g., NETD and the operability of MWIR and LWIR 1280×1024 FPAs with MCT layers grown on GaAs by MBE.
Situational awareness and precise targeting at day, night and severe weather conditions are key elements for mission
success in asymmetric warfare. To support these capabilities for the dismounted soldier, AIM has developed a family of
stand-alone thermal weapon sights based on high performance cooled IR-modules which are used e.g. in the
infantryman of the future program of the German army (IdZ). The design driver for these sights is a long ID range
<1500m for the NATO standard target to cover the operational range of a platoon with the engagement range of .50 cal
rifles, 40mm AGLs or for reconnaissance tasks. The most recent sight WBZG has just entered into serial production for
the IdZ enhanced system of the German army with additional capabilities like a wireless data link to the soldier
Minimum size, weight and power (SWaP) are most critical requirements for the dismounted soldiers’ equipment and
sometimes push a decision towards uncooled equipment with marginal performance referring to the outstanding
challenges in current asymmetric warfare, e.g. the capability to distinguish between combatants and non-combatants in
To provide the uncompromised e/o performance with SWaP parameters close to uncooled, AIM has developed a new
thermal weapon sight based on high operating temperature (HOT) MCT MWIR FPAs together with a new low power
single piston stirling cooler. In basic operation the sight is used as a clip-on in front of the rifle scope. An additional
eyepiece for stand-alone targeting with e.g. AGLs or a biocular version for relaxed surveillance will be available.
The paper will present details of the technologies applied for such long range cooled sights with size, weight and power
close to uncooled.
Since many years AIM delivers IR-modules for army applications like pilotage, weapon sights, UAVs or vehicle
platforms. State-of-the-art 640x512, 15μm pitch detector modules are in production in manifold configurations
optimized for specific key requirements on system level. This is possible due to a modular design, which is best suited to
meet the diversity of system needs in army applications. Examples are optimization of detector-dewar length for gimbal
applications, size weight and power reduction for UAVs or lifetime enhancement for vehicle platforms.
In 2012 AIM presented first prototypes of megapixel detectors (1280x1024, 15μm pitch) for both spectral bands MWIR
and LWIR. These large format detector arrays fulfill the demand for higher spatial resolution, which is requested for
applications like rotorcraft pilotage, persistent surveillance or tasks like determination of threat level in personnel targets.
Recently, a new tactical dewar has been developed for the 1280x1024 detector arrays. It is designed to withstand
environmental stresses and, at the same time, to quest for a compact overall package. Furthermore, the idea of a modular
design will be even more emphasized. Integration of different cooler types, like AIM’s SX095 or rotary integral, will be
possible without modification of the dewar.
The paper will present development status of large format IR-modules at AIM as well as performance data and
configuration considerations with respect to army applications.
Current trends on the enhancement of MCT FPA IR-modules are reduction of size, weight and power (SWaP), increase
of resolution with large detector arrays, provision of staring LWIR or dual-band capability. This is achieved by
reduction of pixel size, higher operating temperatures (HOT) or complex pixel structures together with the optimization
of dewars, adapted cooling engines and proximity electronics.
To meet these demands AIM is working on MCT single-band MWIR or LWIR modules with formats 640x512 or
1280x1024 in 15μm pitch and a dual-band MWIR/LWIR module 640x512 in 20μm pitch. As a first step high operating
temperatures for MWIR 120K and LWIR 80K were demonstrated, development for MWIR >= 150K and LWIR >=
90K is ongoing. The modules are realized as integrated detector cooler assemblies (IDCA) with proximity electronics.
The 640x512/15μm pitch modules are already available in application specific configurations e.g. having integral rotary
or split linear cooling engines.
Besides implementation of the above mentioned capabilities also improvement in long term and cycle stability of IRmodules
has been achieved which is important to fully benefit from increased mission times and longer maintenance
periods by HOT. Especially staring MCT LWIR modules so far required sophisticated non-uniformity correction
(NUC) processing to provide acceptable long term image quality while former scanning systems usually used
implemented temperature references for NUC update. For a thermal imager setup with the LWIR 640x512/15μm
module two-point correction with factory calibrated gain coefficients together with a new offset calibration after every
cool down cycle is used.
The paper will present the results of AIM's current staring single-band MCT IR-modules in MWIR or LWIR
configuration especially regarding to their long term and cycle stability.
Current development efforts in IR-module technology show two major trends: reducing size, weight and power (SWaP)
of IR-systems and further increase of system performance by introducing 3rd Gen IR-modules.
The key elements to reduce SWaP as well as cost while keeping high electro-optical performance are further reduction of
pitch size, implementing compact and low power cooling engines and provide more cost-efficient production of detector
arrays. In this paper latest results of IR-detectors (640x512, 15μm pitch) operating at high operation temperatures (HOT)
are presented. HOT is the fundamental requirement for achieving above mentioned goals.
For advanced reduction of SWaP AIM started the development of a full TV format detector array with 640x480 elements
and 12μm pitch size.
Megapixel detectors having e.g. 1280x1024 elements belong to next generation of IR-modules and are state-of-the-art
choice for the demand of high performance applications for maximum possible spatial resolution.
The development status of these large format 2-dimensional detector arrays at AIM will be shown in the paper.
Application requirements driving present IR technology development activities are improved capability to detect and identify a threat as well as the need to reduce size weight and power consumption (SWaP) of thermal sights. In addition to the development of 3rd Gen IR modules providing dual-band or dual-color capability, AIM is focused on IR FPAs with reduced pitch and high operating temperature for SWaP reduction. State-of-the-art MCT technology allows AIM the production of mid-wave infrared (MWIR) detectors operating at temperatures exceeding 120 K without any need to sacrifice the 5-μm cut-off wavelength. These FPAs allow manufacturing of low cost IR modules with minimum size, weight, and power for state-of-the-art high performance IR systems. AIM has realized full TV format MCT 640×512 mid-wave and long-wave IR detection modules with a 15-μm pitch to meet the requirements of critical military applications like thermal weapon sights or thermal imagers in unmanned aerial vehicles applications. In typical configurations like an F/4.6 cold shield for the 640×512 MWIR module an noise equivalent temperature difference (NETD) <25 mK @ 5 ms integration time is achieved, while the long-wavelength infrared (LWIR) modules achieve an NETD <38 mK @ F/2 and 180 μs integration time. For the LWIR modules, FPAs with a cut-off up to 10 μm have been realized. The modules are available either with different integral rotary cooler configurations for portable applications that require minimum cooling power or a new split linear cooler providing long lifetime with a mean time to failure (MTTF) > 20000, e.g., for warning sensors in 24/7 operation. The modules are available with optional image processing electronics providing nonuniformity correction and further image processing for a complete IR imaging solution. The latest results and performance of those modules and their applications are presented.
3rd generation IR modules - dual-color (DC), dual-band (DB), and large format two-dimensional arrays - require
sophisticated production technologies such as molecular beam epitaxy (MBE) as well as new array processing
techniques, which can satisfy the rising demand for increasingly complex device structures and low cost detectors. AIM
will extend its future portfolio by high performance devices which make use of these techniques. The DC MW / MW
detectors are based on antimonide type-II superlattices (produced by MBE at Fraunhofer IAF, Freiburg) in the 384x288
format with a 40 μm pitch. For AIM, the technology of choice for MW / LW DB FPAs is MCT MBE on CdZnTe
substrates, which has been developed in cooperation with IAF, Freiburg. 640x512, 20 μm pitch Focal Plane Arrays
(FPAs) have been processed at AIM. The growth of MW MCT MBE layers on alternate substrates is challenging, but
essential for competitive fabrication of large two-dimensional arrays such as megapixel (MW 1280x1024, 15 μm pitch)
FPAs. This paper will present the development status and latest results of the above-mentioned 3rd Gen FPAs and
Integrated Detector Cooler Assemblies (IDCAs).
Low size, weight and power (SWaP) are the most critical requirements for portable thermal imagers like weapon sights
or handheld observations devices. On the other hand due to current asymmetrical conflicts there are high requirements
for the e/o performance of these devices providing the ability to distinguish between combatants and non-combatants in
adequate ranges. Despite of all the success with uncooled technology, such requirements usually still require cooled
detectors. AIM has developed a family of thermal weapon sights called HuntIR and RangIR based on high performance
cooled IR-modules which are used e.g. in the infantryman of the future program of the German army (IdZ). The specific
capability of these devices is a high ID range >1500m for tank targets being suitable in use as thermal sights for .50 cal
rifles like the G82, targeting units for the 40mm AGL or for night observation. While such ranges sound far beyond the
operational needs in urban operations, the a.m. specific needs of asymmetric warfare require sometimes even more
High operating temperature (HOT) is introduced in the AIM MCT 640x512/15μm MWIR or LWIR modules for further
reduction of cooler power consumption, shorter cooldown times and higher MTTF. As a key component to keep
performance while further reducing SWaP AIM is developing a new cooled MCT IR-module with reduced pitch of 12
μm operating at a temperature >120 K. The module will provide full TV format with 640x480 elements sensitive in the
MWIR spectral band.
The paper will show recent results of AIM IR-modules with high operating temperature and the impact of design
regarding the IR-module itself and thermal sights making use of it.
InAs/GaSb short-period superlattices (SL) have proven their large potential for high performance focal plane array
infrared detectors. Lots of interest is focused on the development of short-period InAs/GaSb SLs for mono- and bispectral
infrared detectors between 3 - 30 μm. InAs/GaSb short-period superlattices can be fabricated with up to 1000
periods in the intrinsic region without revealing diffusion limited behavior. This enables the fabrication of InAs/GaSb SL
camera systems with very high responsivity, comparable to state of the art CdHgTe and InSb detectors. The material
system is also well suited for the fabrication of dual-color mid-wavelength infrared InAs/GaSb SL camera systems.
These systems exhibit high quantum efficiency and offer simultaneous and spatially coincident detection in both spectral
An essential point for the performance of two-dimensional focal plane infrared detectors in camera systems is the
number of defective pixel on the matrix detector. Sources for pixel outages are manifold and might be caused by the
dislocation in the substrate, the epitaxial growth process or by imperfections during the focal plane array fabrication
process. The goal is to grow defect-free epitaxial layers on a dislocation free large area GaSb substrate. Permanent
improvement of the substrate quality and the development of techniques to monitor the substrate quality are of particular
importance. To examine the crystalline quality of 3" and 4" GaSb substrates, synchrotron white beam X-ray topography
(SWBXRT) was employed. In a comparative defect study of different 3" GaSb and 4" GaSb substrates, a significant
reduction of the dislocation density caused by improvements in bulk crystal growth has been obtained. Optical
characterization techniques for defect characterization after MBE growth are employed to correlate epitaxially grown
defects with the detector performance after hybridization with the read-out integrated circuit.
An increasing need for high-precision atmospheric data especially in the long wavelength infrared (LWIR) and very long
wavelength infrared (VLWIR) spectral ranges has arisen in the past years not only for the analysis of climate change and
its effect on the earth's ecosystem, but also for weather forecast and atmospheric monitoring purposes.
Spatially and spectrally resolved atmospheric emission data are advantageously gathered through limb or nadir sounding
using an imaging Fourier transform (FT) interferometer with a two-dimensional (2D) high-speed focal plane detector
In this paper, AIM reports on its latest results on MCT VLWIR FPAs for Fourier transform infrared sounding
applications in the 8-15μm spectral range. The performance of a (112x112) pixel photodiode array with a 40μm pixel
pitch incorporating extrinsic p-doping for low dark current, a technique for linearity improvement at high photon fluxes,
pixel guards, pixel select/de-select, and a (2x2) super-pixel architecture is discussed. The customized read-out integrated
circuit (ROIC) supporting integrate while-read (IWR) operation has a buffered direct injection (BDI) input stage and a
full well capacity (FWC) of 143 Megaelectrons per super-pixel. It consists of two independently operating halves with
two analog video outputs each. The full frame rate is typically 4k frames/sec, making it suitable for use with rapid scan
FT infrared spectrometers.
At a 55K operating temperature and an ~14.4μm cut-off wavelength, a photo response of 12.1mV/K and a noise
equivalent temperature difference of 24.8mK at half well filling are demonstrated for a 286K reference scene. The nonlinearity
error is <0.5%.
Additional to the development of 3rd Gen IR modules like dual-band and dual-color devices AIM is focused on IR
FPAs with reduced pitch. These FPAs allow manufacturing of compact low cost IR modules with minimum power
consumption for state-of-the-art high performance IR systems.
AIM has realized full TV format MCT 640x512 mid-wave and long-wave IR detection modules with a 15 μm pitch to
meet the requirements of critical military applications like thermal weapon sights or thermal imagers in UAV
applications. In typical configurations like a F/4.6 cold shield for the 640x512 MWIR module an NETD < 25 mK @ 5
ms integration time is achieved, while the LWIR modules achieve an NETD < 38 mK @ F/2 and 180 μs integration
time. For the LWIR modules FPAs with a cut-off of 9 and 10 μm have been realized. The modules are available either
with different integral rotary cooler configurations for portable applications which require minimum cooling power or a
new split linear cooler providing long lifetime with a MTTF > 20,000 h as required e.g. for warning sensors in 24/7
The modules are available with an optional image processing electronics providing non-uniformity correction and
further image processing for a complete IR imaging solution. A double field of view FLIR for an upgrade of the
German Army UAV LUNA has been developed by AIM using the MCT 640x512 MWIR 15μm pitch engine.
The latest results and performance of those modules and their applications are presented.
InAs/GaSb short-period superlattices (SL) based on GaSb, InAs and AlSb have proven their great potential for high
performance infrared detectors. Lots of interest is currently focused on the development of short-period InAs/GaSb SLs
for advanced 2nd and 3rd generation infrared detectors between 3 - 30 μm. For the fabrication of mono- and bispectral
thermal imaging systems in the mid-wavelength infrared region (MWIR) a manufacturable technology for high
responsivity thermal imaging systems has been developed. InAs/GaSb short-period superlattices can be fabricated with
up to 1000 periods in the intrinsic region without revealing diffusion limited behavior. This enables the fabrication of
InAs/GaSb SL camera systems with high responsivity comparable to state of the art CdHgTe and InSb detectors. The
material system is also ideally suited for the fabrication of dual-color MWIR/MWIR InAs/GaSb SL camera systems with
high quantum efficiency for missile approach warning systems with simultaneous and spatially coincident detection in
both spectral channels.
The mission success of the geostationary operational satellite system Meteosat Third Generation (MTG) will
significantly depend on the instrument performance in the very long wavelength infrared (VLWIR) spectral range. As far
as dark current behavior, homogeneity, and operability are concerned, the VLWIR constitutes a major challenge for
sensor material improvement and device development. This paper reports on the latest results on HgCdTe (MCT)
VLWIR photovoltaic sensor development and characterization for possible use with MTG.
In order to achieve low enough dark currents, extrinsically p-doped MCT material with various cut-off wavelengths in
the long wavelength infrared (LWIR)/VLWIR has been developed and manufactured. Compared to standard intrinsic
MCT, a reduction in dark current by more than an order of magnitude is achieved, meeting the challenging MTG
In a (256x256) VLWIR MCT focal plane array (FPA) with an ~14.7μm cut-off wavelength at a 55K operating
temperature, a dark current density of about 1pA/μm2 is demonstrated. For a 291K reference scene and at half-well
integration capacity, we obtain a noise equivalent temperature difference of (24.0±3.0)mK and a photo response of
The predominant spectral bands for IR applications are the 3-5μm MWIR and 8-10μm LWIR. AIM covers all these
bands since many years with a mature MCT technology. For weight, size, power consumption and - last but not least -
cost reduction, detection modules for these applications move to a pitch of 15μm. This is in both bands still a good
match referring to the optical blur spot size and detector performance. Due to the compact design, the modules are
equally well suited for new programs as well as retrofits of 1st GEN systems.
Typical configurations at AIM are a 640x512 MWIR module, achieving an NETD < 25 mK @ F/4.6 and 5 ms
integration time equivalent to half well fill conditions and an LWIR version with NETD < 30 mK @ F/2 and 110μs
integration time. The modules are available either with an integral rotary cooler for portable applications which require
minimum cooling power or a split linear cooler with a flexure bearing compressor providing long lifetimes with a
MTTF >20,000h as required e.g. for warning sensors in 24/7 operation.
A new field of applications supplied by AIM is the short wave infrared SWIR. The major advantage of MCT, the
tunable bandgap i.e. cut-off wavelength, allows to match various requirements. So far specifically driven by spaceborne
programs, a 1024x256 SWIR focal plane array (FPA) integrated detector cooler assembly (IDCA) with flexure bearing
cooler and pulse tube cold finger was developed. The same technology including charge transimpedance amplifier for
the low flux in the SWIR is available in a half TV 384x288 configuration. The read-out integrated circuit (ROIC)
provides among other features 8 outputs for high frame rates up to 450Hz.
Again for spaceborne commercial but also military applications like sensors in ballistic missile defense systems AIM
develops MCT based very long wave (VLWIR) detectors with a cut-off wavelength >15μm.
The current status and trends at AIM on IR detection modules sensitive in spectral ranges from short wave IR (SWIR)
to very long wave IR (VLWIR) together with the requirements of the demanding applications are summarized.
In all recent missions our forces are faced with various types of asymmetric threads like snipers, IEDs, RPGs or
MANPADS. 2nd and 3rd Gen IR technology is a backbone of modern force protection by providing situational
awareness and accurate target engagement at day/night. 3rd Gen sensors are developed for thread warning capabilities
by use of spectral or spatial information. The progress on a
dual-color IR module is discussed in a separate paper .
A 1024x256 SWIR array with flexure bearing compressor and pulse tube cold finger provides > 50,000h lifetime for
space or airborne hyperspectral imaging in pushbroom geometry with 256 spectral channels for improved change
detection and remote sensing of IEDs or chemical agents. Similar concepts are pursued in the LWIR with either
spectroscopic imaging or a system of LWIR FPA combined with a cooled tunable Laser to do spectroscopy with
stimulated absorption of specific wavelengths.
AIM introduced the RangIR sight to match the requirements of sniper teams, AGLs and weapon stations, extending the
outstanding optronic performance of the fielded HuntIR with position data of a target by a laser range finder (LRF), a 3
axis digital magnetic compass (DMC) and a ballistic computer for accurate engagement of remote targets. A version
with flexure bearing cooler with >30,000h life time is being developed for continuous operation in e.g. gunfire detection
systems. This paper gives an overview of AIM's technologies for enhanced force protection.
3rd Generation IR detectors providing e.g. dual-color capability are of great benefit for applications like aircraft missile approach warning systems using this feature for achieving low false alarm rates by separating the hot CO2 missile plume from background and clutter. AIM and IAF selected antimonide based type II Superlattices (SL) for such kind of applications. The type II SL technology provides an accurate engineering of sensitive layers by MBE with very good homogeneity and yield. IAF and AIM already managed to realize a dual-color 384x288 IR-Module based on this technology. It combines spectral selective detection in the 3-4 &mgr;m wavelength range and 4-5 &mgr;m wavelength range in each pixel with coincident integration in a 384x288x2 format and 40 &mgr;m pitch. Excellent thermal resolution with NETD < 17 mK @ F/2, 2.8 ms for the longer wavelength range (red color) and NETD < 30 mK @ F/2, 2.8 ms for the shorter wavelength range (blue color) were already reported. In order to increase further the quantum efficiency and subsequently decrease further the spectral crosstalk between the two colors the layer thickness of the SL-layer was optimized.
This paper is intended to present the current status and trends at AIM on antimonide type II Superlattices (SL) IR module developments for ground and airborne applications in the high performance range, where rapidly changing scenes - like e.g. in case of missile warning applications for airborne platforms - require temporal signal coincidence with integration times of typically 1ms.
In recent years, the interest in infrared imaging systems has broadened from the classical MWIR (3-5 &mgr;m) and LWIR
(8-12 &mgr;m) spectral bands to the SWIR (1-3 &mgr;m) and VLWIR (12-15 &mgr;m). The atmospheric transmission windows
(MWIR, LWIR) are the preferred spectral region for panchromatic night vision systems to display temperature contrasts.
Whereas the characteristic absorption and emission signatures in the SWIR and VLWIR make these bands well suited
for remote sensing of material composition (hyperspectral imaging). In the standard bands, AIM has constantly
improved homogeneity and reduced the number of defects of its FPAs. We obtain for instance 0.38% defective pixels
for 384 x 288 LW arrays. Our FPAs withstand >9'000 thermal cycles without degradation. The improved reliability is
based on substrate removal and applying a thermally matched underfiller. For hyperspectral imaging applications, a
1024 x 256 SWIR array with 245 Hz frame rate for low photon fluxes with CTIA input stage was developed. For
VLWIR applications we built a 256 x 256 array with 880 Hz frame rate that has a cut-off wavelength of >13 &mgr;m at 40 K.
AIM's IR detectors cover the whole spectral range from 0.9 to 13 &mgr;m.
The 3rd generation of infrared (IR) detection modules is expected to provide advanced features like higher resolution
1024x1024 or 1280x720 pixels and/or new functions like multicolor or multi band capability, higher frame rates and
better thermal resolution. This paper is intended to present the current status and trends at AIM on antimonide type II
superlattices (SL) dual color detection module developments for ground and airborne applications in the high
performance range, where rapidly changing scenes - like e.g. in case of missile warning applications for airborne
platforms or ground based sniper detection systems - require temporal signal coincidence with integration times of
AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The type II SL
technology provides - similar to QWIP's - an accurate engineering of sensitive layers by MBE with very good
homogeneity and yield. IAF and AIM managed already to realize a dual color 384x288 IR module based on this
technology. It combines spectral selective detection in the 3 - 4&mgr;m wavelength range and 4 - 5 &mgr;m wavelength range in
each pixel with coincident integration in a 384x288x2 format and 40x40 &mgr;m2 pitch. Excellent thermal resolution with
NETD < 12 mK @ F/2, 2.8 ms for the longer wavelength range (red band) and NETD < 22 mK @ F/2, 2.8 ms for the
shorter wavelength range (blue band) were reported.
In the meantime a square design of 256x256x2 pixel with a reduced pitch of 30x30 &mgr;m2 is in preparation. In this case
with 2 Indium bumps per pixel and a third common contact for all pixels required for temporal coincidence is connected
at the outer area of the array. The fill factor is approx. 65% for both wavelength ranges. The reduced size of the array
enables the use of a smaller dewar with reduced cooling power and significantly reduced weight and broadens the scope
of applications where weight and costs is essential. Design aspects and expected performances are discussed.
Remote sensing from space is an emerging market for applications in security, climate research, weather forecast, and global environmental monitoring, to mention a few. In particular, next generation systems demand for large, two-dimensional arrays in the short (SWIR, 0.9-2.5 μm) and the very long wavelength infrared (VLWIR) spectral range up to 15 μm. AIM's developments for space applications benefit from AIM's experiences in high-performance thermal imaging and seeker-head applications. AIM has delivered a 13 μm cut-off demonstrator for a high resolution Fourier-transform imaging spectrometer in limb geometry. For this 256 x 256 VLWIR sensor we measured a responsivity of 100 LSB/K and a noise equivalent temperature difference of 22 mK with 14 bit ADCs at 880 Hz full frame-rate. The substrate and epitaxial layer grown at AIM exhibit very good uniformity and low dark currents. Currently, AIM develops a 1024 x 256 SWIR detector (0.9-2.5 μm) with a capacitance transimpedance amplifier (CTIA) for hyperspectral imaging. The radiation hardness of AIM's FPA technology (MCT sensor and Silicon read-out integrated circuit) has been successfully tested by a total ionization dose (TID) experiment using ESTEC's 60Co γ-source. Our reference module withstands 30 krad TID. For enhanced reliability of the IDCA, AIM has developed a compact 1 W pulse-tube cooler with flexure bearing compressor, which induces also a very low vibration output. In summary, AIM will be able to supply space qualified detector modules covering the spectral range from 0.9 to 13 μm in the near future.
This paper is intended to present firstly the current status at AIM on quantum well (QWIP) and antimonide superlattices (SL) detection modules for multi spectral ground and airborne applications in the high performance range i.e. for missile approach warning systems and secondly presents possibilities with long linear arrays i.e. 576x7 MCT to measure spectral selective in the 2 - 11μm wavelength range.
QWIP and antimonide based superlattice (SL) modules are developed and produced in a work share between AIM and the Fraunhofer Institute for Applied Solid State Physics (IAF). The sensitive layers are manufactured by the IAF, hybridized and integrated to IDCA or camera level by AIM. In case of MCT based modules, all steps are done by AIM.
QWIP dual band or dual color detectors provide good resolution as long as integration times in the order of 5-10ms can be tolerated. This is acceptable for all applications where no fast motions of the platform or the targets are to be expected.
For spectral selective detection, a QWIP detector combining 3-5 μm (MWIR) and 8-10 μm (LWIR) detection in each pixel with coincident integration has been developed in a 384x288x2 format with 40 μm pitch. Excellent thermal resolution with NETD < 30 mK @ F/2, 6.8 ms for both peak wavelengths (4.8 μm and 8.0 μm) has been achieved. Thanks to the well established QWIP technology, the pixel outage rates even in these complex structures are well below 0.5% in both bands. The spectral cross talk between the two wavelength bands is equal or less than 1%. The substrate on the sensitive layer of the FPA was completely removed in this case and as a consequence the optical crosstalk in the array usually observed in QWIP arrays resulting in low MTF values was suppressed resulting in sharp image impression.
For rapidly changing scenes - like e.g. in case of missile warning applications for airborne platforms - a material system with higher quantum efficiency is required to limit integration times to typically 1ms. AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The type II SL technology provides - similar to QWIPs - an accurate engineering of sensitive layers by MBE with very good homogeneity and potentially good yield and resistivity against high temperature application i.e. under processing or storage. While promising results on single SL pixels have been reported since many years, so far no SL based detection module could be realized with reasonable performances. IAF and AIM last year managed to realize first most promising SL based detectors. Fully integrated IDCAs with a MWIR SL single color device with 256x256 pixels in 40 μm pitch have been integrated and tested. In the next step the pitch was reduced to 24μm in a 384x288 pixel configuration. With this design and further improved technology a very good pixel operabilities with very low cluster sizes (≤ 4 pixel) and performances with quantum efficiencies as high as known from MCT is reached in the meantime.
A dual color device based on SL technology on the existing 384x288 read-out circuit (ROIC) as used in the dual band QWIP device is available. It combines spectral selective detection in the 3-4.1 μm wavelength range and 4.1-5 μm wavelength range in each pixel with coincident integration in a 384x288x2 format and 40 μm pitch. Excellent thermal resolution with NETD < 17 mK @ F/2, 2.8 ms for the longer wavelength range (red band) and NETD < 30 mK @ F/2, 2.8 ms for the shorter wavelength range (blue band) has been achieved. The pixel outage rates remains below 1% in both colors. The spectral cross talk of the red band to the blue band is estimated below 1%o which is important to reduce significantly the false alarm rate in missile approach warning systems as the primarily intended use of the dual color detector is.
Real time analysis of gases, i.e. the detection of toxic or agent gases, by multi spectral detection in the IR used the characteristic infrared emission or absorption lines of different gas types. Spectroscopic systems consisting of a spectrometer with the need for large linear MCT array with small pixel sizes are used in this case. Possibilities are outlined to use long linear arrays, such as the 576x7 MCT detector, to perform spectral selective measurements in the 2-11μm wavelength range. For these applications a 576x7 MCT FPA is integrated in an open dewar cooler assy without window able to operate directly coupled in an evacuated and cooled spectrometer. The sensitivity of the array is consequently not limited by the transmission of a window for vacuum conservation in the full sensitive wavelength range of MCT up to the cut-off of 10.5 μm.
The 3rd generation of infrared (IR) detection modules is expected to provide advanced features like higher resolution 1024x1024 or 1280x720 pixels and/or new functions like multicolor or multi band capability, higher frame rates and better thermal resolution. This paper is intended to present the current status at AIM on quantum well (QWIP) and antimonide superlattices (SL) detection modules for ground and airborne applications in the high performance range. For spectral selective detection, a QWIP detector combining 3-5μm (MWIR) and 8-10μm (LWIR) detection in each pixel with coincident integration has been developed in a 384x288x2 format with 40 μm pitch. Excellent thermal resolution with NETD < 30mK @ F/2, 6.8 ms for both peak wavelengths (4.8 μm and 8.0 μm) has been achieved. Thanks to the well established QWIP technology, the pixel outage rates even in these complex structures are below 0.5% in both bands. QWIP dual band or dual color detectors provide good resolution as long as integration times in the order of 5-10ms can be tolerated. This is acceptable for all applications where no fast motions of the platform or the targets are to be expected. For rapidly changing scenes-like e.g. in case of missile warning applications for airborne platforms-a material system with higher quantum efficiency is required to limit integration times to typically 1ms. AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The SL technology provides-similar to QWIP's-an accurate engineering of sensitive layers by MBE with very good homogeneity and yield. While promising results on single SL pixels have been reported since many years, so far no SL based detection module could be realized. IAF and AIM last year managed to realize first most promising SL based detectors. Fully integrated IDCA's with a MWIR SL device with 256x256 pixels in 40µm pitch have been integrated and tested. The modules exhibit excellent thermal resolution of NETD<10mk @ F/2 and 5ms. Product improvement meanwhile allowed to reduce pixel outage rates below 1% i.e. down to a level as required for the military use of such detectors. Presently under development is therefore a dual color MWIR device based on SL technology and the existing 384x288 read out circuit (ROIC) used in the dual band QWIP device. This detector is primarily intended for the use in missile approach warning systems where the dual color capability significantly improves suppression of false alarms. Details of the modules and results of the electrooptical performance will be presented for the different items mentioned above.
The 3rd generation of infrared (IR) detection modules is expected to provide advanced features like higher resolution 1024x1024 or 1280x720 pixels and/or new functionalities like multicolor or multi band capability, higher frame rates and better thermal resolution. This paper is intended to present the current status at AIM on the Mercury Cadmium Telluride (MCT), quantum well (QWIP) and antimonide superlattices (SL) detection modules for ground and airborne applications in the high performance range. For high resolution a 1280x720 MCT device in the 3-5μm range (MWIR) is presently under development. For spectral selective detection, a QWIP detector combining MWIR and 8-10μm (LWIR) detection in each pixel has been developed in a 384x288x2 format with 40 μm pitch, NETD < 35mK @ F/2, 6,8 ms for both peak wavelengths (4.8 μm and 8.0 μm). The device provides synchronous integration of both bands for temporal and spatial coincidence of the events observed. QWIP dual band or dual color detectors provide good resolution as long as integration times in the order of 5-10ms can be tolerated. This is acceptable for all applications where no fast motions of the platform or the targets are to be expected. For rapidly changing scenes - like e.g. in case of missile warning applications for airborne platforms - a material system with higher quantum efficiency is required to limit integration times to typically 1ms. For this case, several companies work on molecular beam epitaxy (MBE) of MCT to have access to double or multi layer structures. AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The SL technology provides -- similar to QWIP's -- an accurate engineering of sensitive layers by MBE with very good homogeneity and yield. While promising results on single SL pixels have been reported since many years, so far no SL based detection module could be realized. Just recently, IAF and AIM managed to realize first most promising SL based detectors. Fully integrated IDCAs with a MWIR SL device with 256 x 256 pixels in 40 μm pitch have been integrated and tested. The modules exhibit excellent thermal resolution of NETD > 12 mk @ F/2 and 5 ms. The next step will now be to stabilize the technology and to start the development of a dual color MWIR device based on SL technology and the existing 384 x 288 read out circuit (ROIC) used in the dual band QWIP device.
The 3rd generation of infrared (IR) detection modules is expected to provide higher video resolution, advanced functions like multi band or multi color capability, higher frame rates, and better thermal resolution. AIM has developed staring and linear high performance focal plane arrays (FPA) integrated into detector/dewar cooler assemblies (IDCA). Linear FPA’s support high resolution formats such as 1920 x 1152 (HDTV), 1280 x 960, or 1536 x 1152. Standard format for staring FPA’s is 640 x 512. In this configuration, QEIP devices sensitive in the 8 - 10 µm band as well as MCT devices sensitive in the 3.4 - 5.0 µm band are available. A 256 x 256 high speed detection module allows a full frame rate >800 Hz. Especially usability of long wavelength devices in high performance FLIR systems does not only depend on the classical electrooptical performance parameters such as NEDT, detectivity, and response homogeneity, but are mainly characterized by the stability of the correction coefficients used for image correction. The FPA’s are available in suited integrated detector/dewar cooler assemblies. The linear cooling engines are designed for maximum stability of the focal plane temperature, low operating temperatures down to 60K, high MTTF lifetimes of 6000h and above even under high ambient temperature conditions. The IDCA’s are equipped with AIM standard or custom specific command and control electronics (CCE) providing a well defined interface to the system electronics. Video output signals are provided as 14 bit digital data rates up to 80 MHz for the high speed devices.
To meet the demands for high temperature-cycling reliability of HgCdTe detectors, bonded to a Silicon 'Read-Out-Integrated- Circuit,' AIM has developed a Multi-Chip-Module approach for the infrared Focal-Plane-Array. Bonding of detector array and Si-chips on a sapphire substrate minimizes thermal stress and strain in the FPA, leading to cycle-to-failure of >= 1000. For maximum cycle estimation under varying strain, a correlation was established empirically.
To meet the demands for high performance infrared imaging systems AIM had developed a family of CMT detector modules with linear focal plane arrays, integrated detector cooler assemblies (IDCA), and command and control electronics (CCE). Common features of these modules are focal plane multiplexers with time delay and integration (TDI) function, pixel deselect, programmable gain for each line, bidirectional scan capability, partitioning and global gain select. The family of IDCA's consists either of single chip focal plane arrays (FPA) directly linked to a read out integrated multiplexer (ROIC) by solder bump technique, or one clip infrared detectors connected to one or more ROIC's using a multichip module (MCM) technique, dewars with optimized thermal heat load, coolers with integrated control electronics, and command and control electronics (CCE). The general design of these modules is outlined. Test results are shown.
The last 10 years of engineering and production at AEG INFRAROT-MODULE GmbH (AIM) resulted in continued improvements in performance, yield and reliability of IR modules and cryocoolers. For the optimizing of engineering, production and testing over the complete scope, from semiconductor material growth, FPA fabrication, cryo packaging data processing and software, cooling, etc. up to the camera level, AIM has all critical technologies under one roof. This paper demonstrates how such results were achieved, which criteria are to be met for performance, yield and cost improvements and how contemporary IR modules from AIM reflect these achievements.
AEG has successfully developed a family of PtSi detection modules to cover various applications. The development was performed in a cooperation with Daimler Benz Research and Technology F2M and Telefunken Microelectronic TEMIC EZIS. The modules are designed around 2 staring PtSi focal plane arrays (FPA) having 256 X 256 pixels or 640 X 486 pixels, respectively. Both arrays are identical in their basic features like 24 micrometers pitch, > 60% fillfactor, variable integration time, optional interlaced and non interlaced rolling frame readout, subframe capability and excellent thermal resolution with measured values for the NETD < 70 mK (300 K, 20 ms, F/1.4). The FPA's are integrated either in integrated dewar cooler assemblies with a 1/3 W split linear compressor for the 256 X 256 FPA or a 1 W split linear compressor for the 640 X 486 FPA, respectively, or designed for the use in seeker applications with a Joule Thomson cryocooler (640 X 486 FPA only). The modules are completed by different miniaturized types of electronics, providing all DC and clock supplies to drive the FPA's and providing the customer with either a buffered analog or a 14 Bit resolution digital interface. Digital signal processor (DSP) based image correction units were developed for testing the units. The DSP boards provide the ability for freely programmable real-time functions like 2 point correction or other data manipulations in camera applications. The modules and their key features are reviewed together with their performance data.
A hybrid 256 X 256 PtSi focal plane array (FPA) with single output CMOS multiplexer readout in 24 micrometers pitch has successfully been developed. The device combines an excellent analog performance like noise equivalent temperature difference NETD < 100 mK (F/1.4, 20 ms, 300 K), dynamics > 12 bit, high output voltage > 2.5 V and reduced blooming with a very flexible digital layout, that enables customer specific applications like interlaced or progressive readout, variable integration time between 20 to 40 ms frametime and ultrashort times < 10 microsecond(s) , or subframe capability by just switching between clock patterns. The development is done in cooperation with DAIMLER BENZ Research and Technology, Munich, and TELEFUNKEN microelectronic TEMIC EZIS, Ulm. Reported are the digital features of the multiplexer results of the hybridization process and test results of our most recent FPA's. An outlook is given on the just started development of a 486 X 640 FPA with identical features, and on the development of integrated dewar cooler assemblies for this detector generation.