The first HgCdTe (MCT) activities at AEG-Telefunken in Germany were started in 1976. As part of the closing of AEG, the Heilbronn based IR-technology division was established as a spin-off company in 1995, under the brand name of AIM Infrarot-Module GmbH. A rapidly growing team of scientists focused on the detector-dewar-cooler technology and the development of linear photoconductive MCT arrays by applying the solid-state-recrystallization (SSR) technique for MCT growth, depositing and thinning MCT on sapphire substrates and oxide passivation. In 1979, after successful development of an own MCT-technology base, AEG-Telefunken entered into a license agreement with Texas Instruments for US Common Module (CM) technology in order to speed up the entry into full scale production with a transfer of MCT-material, dewar and cooler processes. CMs are still manufactured in small numbers. At the same time, a proprietary pc-MCT technology, independent of the CM production line, was developed and continuously matured and is today successfully applied in various custom designs like detectors for smart ammunition, for commercial and space applications. In 1982 started the development of 2nd Gen. photovoltaic MCT detectors, based on liquid-phase-epitaxy (LPE) in tilting and dipping technique and on planar array technology with Hg-Diffusion and ion implantation for pn-junction formation and CdTe/ZnS passivation. Linear MCT arrays in the 8-10,5 μm wavelength range with state of the art electro-optical performance have rapidly been demonstrated. Within the frame of the European anti-tank program TRIGAT, a two-way know-how-transfer between AEGTelefunken and SOFRADIR was established for linear LW MCT array processing, flip-chip-technology and dewar technology. Today, AIM's 2nd Gen. portfolio is based on MCT-LPE in dipping technique on CdZnTe substrates, characterized by a very low defect and dislocation density for 0,9 μm to 15μm wavelength application. Array processing is performed by planar technique, Boron ion implantation, CdTe/ZnS passivation and intrinsic or extrinsic doping, respectively. Infrared systems with AIM's linear and 2-dim. Focal-Phase-Arrays are used in many state of the art programs in Germany and internationally for surveillance and targeting, seeker head systems or for spaceborne applications like e.g. hyperspectral imaging. AIM's current MCT developments include for example MW/LW-MBE-MCT layers and array processing for 3rd Gen. detectors, avalanche NIR-MCT photodiodes for low background application, MBE on 4" alternative substrates and 2- dim. arrays with very long 15μm cut-off for space-based application to meet the future demands of IR-systems.

The fabrication and optimization of InAs/GaSb type-II superlattice (SL) detectors for single-color and dual-color focal plane arrays in the mid-wavelength infrared spectral range between 3-5 &mgr;m is reported. Single color focal plane arrays with 288 x 384 detector elements and 24 &mgr;m pitch have been fabricated with high pixel yield. Camera systems with InAs/GaSb SL detectors reveal NETD values of 27.9 mK at a cut-off wavelength of &lgr;c = 4.9 &mgr;m for an integration time of only 1 msec with F#/2.4 optics. A dual-color MWIR/MWIR InAs/GaSb SL camera, developed for missile approach warning systems, features simultaneous and spatially coincident detection for both spectral channels on each pixel. The camera system with 288 x 384 detector elements in 40 &mgr;m pitch shows excellent NETD values and high pixel operability. The fabrication of dual-color focal plane arrays on 3" GaSb substrates is presented.

The 3rd generation of infrared (IR) detection modules is expected to provide advanced features like higher resolution 1024x 1024 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 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 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 mu m wavelength range and 4 - 5 mu m wavelength range in each pixel with coincident integration in a 384x288x2 format and 40x40 mu m(2) 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 3000 mu m(2) 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.

AIM has developed a thermal weapon sight HuntIR based on a cooled MCT 384x288 MWIR detection module combining long range battlefield surveillance and target engagement purposes. Since December 2004 the device is in service for the Germany Future Infantryman (IdZ) basic system. To satisfy the demands of the follow-up program German Future Infantryman extended system (IdZ ES) additional components like a laser range finder, digital magnetic compass and a wireless data link will be included to provide e.g. an improved hit rate by accurate range data. To reduce power consumption and increase operation time of the actual device on the one hand and give the possibility to include new components and functions a new optimized command and control electronics and image processing unit was designed using latest digital signal processors resulting in lower power consumption and higher computing power. This allows also an implementation of additional image enhancement functions. The design concept of the upgraded HuntIR is introduced together which the features of the new electronics. Additionally some new implementations will be presented concerning the existing HuntIR device like fire control for the 40mm Grenade Machine Gun made by Heckler&Koch which where possible due to the reprogrammable architecture of the design.Also an uncooled IR Imaging Module designed for use in small UAVs and short range thermal weapon sights was successfully tested in the German Army small UAV ALADIN made by EMT. After the first flight trials the design was revised to incorporate lessons learned including e.g. an athermal lens design to avoid any need of focussing. The features of the revised design will be presented.

We report on bispectral imaging systems based on quantum-well infrared photodetectors (QWIPs) and InAs/GaSb type-II superlattices (SLs) for the mid-wavelength infrared spectral range between 3-5 mu m (MW) and the long-wavelength infrared regime at 8-12 mu m (LW). A dual-band MW/LW QWIP imager and a dual-color MW/MW InAs/GaSb SL camera are demonstrated. The two systems offer a spatial resolution of 288x384 pixels and a simultaneous detection of both channels on each pixel. Both technologies achieve an excellent noise equivalent temperature difference below 30 mK in each channel with F#/2.0 optics.

Focal Plane Arrays for high-performance thermal imaging systems operating in the mid-infrared spectral range between 3–5 µm have been realized by type-II InAs/GaSb short-period superlattices. A fully operational 256 × 256 camera system showing a noise equivalent temperature difference below 10 mK is presented. The suitability of InAs/GaSb type-II superlattices for next generation thermal imagers is demonstrated with the first 288 × 384 dual color demonstrator camera which features a simultaneous and spatially coincident acquisition of two separate spectral regimes in the mid-infrared. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the development of InAs/GaSb type-II superlattice focal plane arrays (FPAs) for missile warning systems in airborne platforms. The FPA fabrication technology was developed on the basis of monospectral superlattices for the MWIR (3-5 mu m) spectral range. A monospectral. 288x384 MWIR camera with 24 mu m pixel pitch, a noise equivalent temperature difference (NETD) better than 14 mK and a background-limited performance (BLIP) up to 92 K is demonstrated. Based on the monospectral technology, the first bispectral superlattice camera was realized. The dual color 288x384 superlattice camera features simultaneous, pixel-registered detection of both spectral channels between 3-4 mu m and 4-5 mu m with a NETD better than 30 mK and 17 m-K, respectively. Hence, spatial or temporal registration problems, which are common to most dual color and dual band infrared imagers are solved with the new bispectral MWIR missile alerting sensor.

The first fully operational mid-IR (3–5 μm) 256×256 IR-FPA camera system based on a type-II InAs/GaSb short-period superlattice showing an excellent noise equivalent temperature difference below 10 mK and a very uniform performance has been realized. We report on the development and fabrication of the detecor chip, i.e., epitaxy, processing technology and electro-optical characterization of fully integrated InAs/GaSb superlattice focal plane arrays. While the superlattice design employed for the first demonstrator camera yielded a quantum efficiency around 30%, a superlattice structure grown with a thicker active layer and an optimized V/III BEP ratio during growth of the InAs layers exhibits a significant increase in quantum efficiency. Quantitative responsivity measurements reveal a quantum efficiency of about 60% for InAs/GaSb superlattice focal plane arrays after implementing this design improvement.

Based on type-II InAs/GaSb superlattice photodiodes, the first report of a dual-colour infrared camera with excellent NETD values < 30 mK for the shortwave channel with a cutoff wavelength of 4.0 mu m and < 17 mK for the longwave channel with 5.0 mu m cutoff is presented. The bispectral system, which offers a simultaneous and pixel-registered detection of both colours, allows remote imaging of carbon dioxide.

We report on the development of InAs/GaSb type-II superlattice focal plane arrays (FPAs) for missile warning systems in airborne platforms. The FPA fabrication technology was developed on the basis of monospectral superlattices for the MWIR (3-5 μm) spectral range. A monospectral 288×384 MWIR camera with 24 μm pixel pitch, a noise equivalent temperature difference (NETD) better than 14 mK and a background-limited performance (BLIP) up to 92 K is demonstrated. Based on the monospectral technology, the first bispectral superlattice camera was realized. The dual color 288×384 superlattice camera features simultaneous, pixel-registered detection of both spectral channels between 3-4 μm and 4-5 μm with a NETD better than 30 mK and 17 mK, respectively. Hence, spatial or temporal registration problems, which are common to most dual color and dual band infrared imagers are solved with the new bispectral MWIR missile alerting sensor.

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.

An infrared camera based on a 256×256 focal plane array (FPA) for the second atmospheric window (3–5 µm) has been realized for the first time with InAs/GaSb short period superlattices (SLs). The SL detector structure with a broken gap type-II band alignment was grown by molecular beam epitaxy on GaSb substrates. Effective bandgap and strain in the superlattice were adjusted by varying the thickness of the InAs and GaSb layers and the controlled formation of InSb-like bonds at the interfaces. The FPAs were processed in a full wafer process using optical lithography, chemical-assisted ion beam etching, and conventional metallization technology. The FPAs were flip-chip bonded using indium solder bumps with a read-out integrated circuit and mounted into an integrated detector cooler assembly. The FPAs with a cut-off wavelength of 5.4 µm exhibit quantum efficiencies of 30% and detectivity values exceeding 10 13 Jones at T=77 K. A noise equivalent temperature difference (NETD) of 11.1 mK was measured for an integration time of 5 ms using f/2 optics. The NETD scales inversely proportional to the square root of the integration time between 5 ms and 1 ms, revealing background limited performance. Excellent thermal images with low NETD values and a very good modulation transfer function demonstrate the high potential of this material system for the fabrication of future thermal imaging systems.

"Network-centric Warfare" is a common slogan describing an overall concept of networked operation of sensors, information and weapons to gain command and control superiority. Referring to IR sensors, integration and fusion of different channels like day/night or SAR images or the ability to spread image data among various users are typical requirements. Looking for concrete implementations the German Army future infantryman IdZ is an example where a group of ten soldiers build a unit with every soldier equipped with a personal digital assistant (PDA) for information display, day photo camera and a high performance thermal imager for every unit. The challenge to allow networked operation among such a unit is bringing information together and distribution over a capable network. So also AIM's thermal reconnaissance and targeting sight HuntIR which was selected for the IdZ program provides this capabilities by an optional wireless interface.Besides the global approach of Network-centric Warfare network technology can also be an interesting solution for digital image data distribution and signal processing behind the FPA replacing analog video networks or specific point to point interfaces. The resulting architecture can provide capabilities of data fusion from e.g. IR dual-band or IR multicolor sensors. AIM has participated in a German/UK collaboration program to produce a demonstrator for day/IR video distribution via Gigabit Ethernet for vehicle applications. In this study Ethernet technology was chosen for network implementation and a set of electronics was developed for capturing video data of IR and day imagers and Gigabit Ethernet video distribution. The demonstrator setup follows the requirements of current and future vehicles having a set of day and night imager cameras and a crew station with several members. Replacing the analog video path by a digital video network also makes it easy to implement embedded training by simply feeding the network with simulation data. The paper addresses the special capabilities, requirements and design considerations of IR sensors and imagers in applications like thermal weapon sights and UAVs for networked operating infantry forces.

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 3-5 mu m (MWIR) and 8-10 mu m (LWIR) detection in each pixel with coincident integration has been developed in a 384x288x2 format with 40 mu m pitch. Excellent thermal resolution with NETD < 30mK @ F/2, 6.8 ms for both peak wavelengths (4.8 mu m and 8.0 mu m) 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 11 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 40 mu m 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.

InAs/GaSb short-period superlattices (SLs) with a broken gap type-II band alignment are investigated for the fabrication of photovoltaic pin-photodetectors on GaSb substrates. The structures were grown by molecular beam epitaxy using valved cracker cells for arsenic and antimony. Effective bandgap and strain in the SL were adjusted by varying the thickness of the InAs and GaSb layers in the SL and the controlled formation of InSb-like or GaAs-like bonds at the interfaces. MBE growth conditions were investigated and optimized in order to achieve good morphological, electrical and optical properties. IR-photodiodes with a cut-off wavelength of 5.4μm reveal quantum efficiencies around 30% and detectivity values exceeding 1013Jones at 77K. A focal plane array camera with 256×256 detector elements and 40μm pitch based on InAs/GaSb short-period SLs was fabricated for the first time. The camera system reveals an excellent thermal resolution with a noise equivalent temperature difference below 12mK for an integration time of 5ms using f/2 optics. The detector performance, comparable with state of the art mercury–cadmium–telluride IR detectors, makes this material system very interesting for the fabrication of advanced thermal imaging systems.

An infrared camera based on a 256x256 focal plane array for the Mid-IR spectral range (3-5 mu m) has been realized for the first time with InAs/GaSb short-period superlattices. The detector shows a cut-off wavelength of 5.4 mu m and reveals a quantum efficiency of 30%. The noise equivalent temperature difference (NETD) reaches 9.4 mK at 73 K with F/2 optics and 6.5 ms integration time. Excellent thermal images with low NETD values and a very good modulation transfer function are presented. Furthermore, a new method to passivate InAs/GaInSb superlattice photodiodes for the 8-10 mu m regime is demonstrated. The approach is based on the epitaxial overgrowth of wet-etched mesa diodes using lattice matched AlGaAsSb. A complete suppression of surface leakage currents in small sized test diodes with 70 mu m diameter is observed.

Quantum well infrared photodetectors (QWIPs) have gained maturity for large focal plane arrays (FPA) with excellent thermal resolution, low 1/f noise, low fixed-pattern noise, and high pixel operability. Due to their spectrally narrow absorption, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. We report on our progress on dual-band QWIP FPAs with pixel-registered, simultaneous integration in both bands. The arrays with 384x288 pixels and 40 μm pitch are based on a photoconductive QWIP for the 3-5 μm regime (MWIR) and a photovoltaic "low-noise" QWIP for 8-12 μm (LWIR). Excellent noise-equivalent temperature differences of only 20.6 mK (LWIR) and 26.7 mK (MWIR) have been achieved at 6.8 ms integration time and f/2 aperture. In addition, we have investigated test devices with different gratings, and discuss their dual-band coupling efficiencies.

We report on the development and status of a dual-band QWIP FPA with 384×288 pixels and 40μm pitch for the 3–5μm (mid-wavelength infrared, MWIR) and 8–12μm (long-wavelength infrared, LWIR) spectral bands. The array is based on a photovoltaic “low-noise” QWIP for the LWIR and a photoconductive QWIP for the MWIR and allows for simultaneous integration of both bands on each pixel. Array histograms indicate a noise-equivalent temperature difference as low as 17mK for the MWIR band and 43mK for the LWIR band at an integration time of 7.6 ms. In addition, we have investigated test devices with different gratings, geometries, and sizes and discuss some tradeoffs for dual-band diffraction gratings.

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 3-5 mum range (MWIR) is presently under development.For spectral selective detection, a QWIP detector combining MWIR and 8-10mum (LWIR) detection in each pixel has been developed in a 384x288x2 format with 40 mum pitch, NETD < 35mK @ F/25 6,8 ms for both peak wavelengths (4.8 mum and 8.0 mum). 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 IDCA's with a MWIR SL device with 256x256 pixels in 40mum pitch have been integrated and tested. The modules exhibit excellent thermal resolution of NETD<12mk @ F/2 and 5ms. 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 384x288 read out circuit (ROIC) used in the dual band QWIP device.

A dual-band focal plane array (FPA) for the 8-12 rhom and 3 5 pm atmospheric windows with simultaneous integration in both spectral bands on each pixel is reported. The FPA is based on quantum well infrared photodetectors and comprises 384 x 288 pixels with 40 mum pitch. At 7.6 ms integration time and an f/2 aperture, the FPA achieves excellent thermal resolution with noise-equivalent temperature differences of 17 mK (3-5 mum) and 43 mK (8-12 mum).