This PDF file contains the front matter associated with SPIE Proceedings Volume 8704, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

We have fabricated low-dark-current InGaAs photodetectors utilizing an epitaxial structure incorporating an InAlGaAs passivation layer and a simple mesa isolation process, and requiring no implant or diffusion steps. At 295 K, areal and perimeter dark current contributions are 15 nA/cm² and 9 pA/cm, respectively, in devices with large aspect ratios biased at -0.1 V. High responsivity was achieved even at zero bias in these devices. Devices were modeled using a commercial drift-diffusion simulator. Good fits to reverse dark current-voltage measurements were obtained using a model that included both bulk and interfacial generation mechanisms. Assuming similar electron and hole Shockley-Read-Hall lifetimes, dark current under small reverse bias are consistent with generation at the interface between the absorber and underlying layers. With increasing negative bias a large increase in dark current is associated with depletion near the InAlGaAs/absorber interface, while small increases in current at large reverse bias suggest long Shockley-Read-Hall lifetimes in the absorber. Forward biasing of these devices results in efficient injection of minority carrier holes into the absorber region, mimicking photogeneration and providing a method to predict the performance of illuminated detector arrays.

SWIR detection band benefits from natural (sun, night glow, thermal radiation) or artificial (eye safe lasers) photons sources combined to low atmospheric absorption and specific contrast compared to visible wavelengths. It gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. The study of InGaAs FPA has begun few years ago with III-VLab, gathering expertise in InGaAs material growth and imaging technology respectively from Alcatel-Lucent and Thales, its two mother companies. This work has led to put quickly on the market a 320x256 InGaAs module. The recent transfer of imagery activities from III-VLab to Sofradir allows developing new high performances products, satisfying customers’ new requirements. Especially, a 640x512 InGaAs module with a pitch of 15µm is actually under development to fill the needs of low light level imaging.

Xenics has designed and manufactured a 1280*1024 pixel, 17 µm pitch InGaAs array for SWIR imaging in the [0.9 - 1.7 µm] range. It will report on the first characterization results of the device. As usual for this type of room temperature operated SWIR image sensors, the detector interface is based on a CTIA stage, yielding excellent linearity, a low detector bias and hence a low and stable dark current combined with low image lag. The charge to voltage conversion factor is 40 µV/e^-. The pixel interface scheme contains a CDS circuit in order to reduce the kTC noise and common mode effects. The noise is expected to be below 30 e^-_rms in linear mode, resulting in a dynamic range < 60 dB. Additionally the linear dynamic range is complemented with a high dynamic range logarithmic response with a saturation level < 5 nA/pixel. The information in the pixel matrix can be read via 2, 4 or 8 outputs, yielding a maximum full frame rate between 50 and 200 Hz. Each output is operating at 40 MHz pixel rate. The outputs are differential with a common mode voltage of 0.9 V and an adjustable output swing of 2 V_ptp. Nevertheless the power dissipation shall be below 330 mW.

Size, weight, and power (i.e.: Small SWaP) are increasingly recognized as the primary drivers in the enablement of high-volume man-portable SWIR imaging systems. Several low power advancements are described for a 1.3 Mpixel SWIR imaging platform capable of operating at a power budget of approximately 1.7 microwatts/pixel. Techniques such as reducing overall system memory bandwidth, low-voltage operation, and parameterized non-uniform corrections (PNUC) are described. Even at such reduced power consumption, full imaging performance at 30 frames per second is realized across an extended operating range of -40°C to 70°C.

SiOnyx has developed visible and infrared CMOS image sensors leveraging a proprietary ultrafast laser semiconductor process technology. This technology demonstrates 10 fold improvements in infrared sensitivity over incumbent imaging technology while maintaining complete compatibility with standard CMOS image sensor process flows. Furthermore, these sensitivity enhancements are achieved on a focal plane with state of the art noise performance of 2 electrons/pixel. By capturing light in the visible regime as well as infrared light from the night glow, this sensor technology provides imaging in daytime through twilight and into nighttime conditions. The measured 10x quantum efficiency at the critical 1064 nm laser node enables see spot imaging capabilities in a variety of ambient conditions. The spectral sensitivity is from 400 to 1200 nm.

We report crosstalk in 1 mm diameter and 2 mm diameter quad InGaAs photodiodes having quadrant-to-quadrant separation of 15 μm, 20 μm, and 25 μm. This crosstalk is a combination of resistive and capacitive coupling between the photodiode quadrants and varies widely on the combination on device diameter, quadrant-to-quadrant separation, illumination conditions, and modulation frequency. Thus, the position sensing accuracy is heavily influenced by the operating conditions of the quad photodiode.

This paper presents novel unit cell architecture for short wave infrared (SWIR) imaging applications. It has two input stages which are CTIA and SFD covering for both respectively low and high light levels and automatic input stage selection circuitry that chooses best input stage. A user can select 2 modes for FPA manual and automatic mode. In manual mode, user can set CTIA or SFD for all pixels according to user needs. In automatic mode, each pixel selects input stage itself according to light level. Automatic input stage selection for each pixel brings high SNR level and low noise along with highest possible dynamic range. Standard CMOS 0.18µm TSMC technology is used to realize unit cell. In the architecture of unit cell, circuit level techniques are used to optimize layout size.

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.

Cooled IR technologies that offer high performances are at the top of DEFIR’s priority list. We have been pursuing further infrared developments on future MWIR detectors, such as the VGA format HOT detector that operates at 150K and the 10μm pitch IR detector which gives us a leading position in innovation In the same time Scorpio LW expands Sofradir's line of small pixel pitch TV format IR detectors from the mid-wavelength to the long-wavelength, broadening the performance attributes of its long wave IR product line. Finally, our dual band MW-LW QWIP detectors (25μm, 384×288 pixels) benefit to tactical platforms giving an all-weather performance and increasing flexibility in the presence of battlefield obscurants. These detectors are designed for long-range surveillance equipment, commander or gunner sights, ground-toground missile launchers and other applications that require higher resolution and sensitivity to improve reconnaissance and target identification. This paper discusses the system level performance in each detector type.

Sensor technologies are undergoing revolutionary advances, as seen in the rapid growth of multispectral methodologies. Increases in spatial, spectral, and temporal resolution, and in breadth of spectral coverage, render feasible sensors that function with unprecedented performance. A system was developed that addresses many of the key hardware requirements for a practical dual-band multispectral acquisition system, including wide field of view and spectral/temporal shift between dual bands. The system was designed using a novel dichroic beam splitter and dual band-pass filter configuration that creates two side-by-side images of a scene on a single sensor. A high-speed CMOS sensor was used to simultaneously capture data from the entire scene in both spectral bands using a short focal-length lens that provided a wide field-of-view. The beam-splitter components were arranged such that the two images were maintained in optical alignment and real-time intra-band processing could be carried out using only simple arithmetic on the image halves. An experiment related to limitations of the system to address multispectral detection requirements was performed. This characterized the system’s low spectral variation across its wide field of view. This paper provides lessons learned on the general limitation of key hardware components required for multispectral muzzle flash detection, using the system as a hardware example combined with simulated multispectral muzzle flash and background signatures.

A fourth generation of SWIR based optical detection and warning means is presented as the EL/O–5220 OTHELLO passive Optical Threat Locator, which detects and precisely finds directions towards a source of battle tank gun fire and missile (e.g. Anti-Tank Guided Missiles (ATGMs) Rocket Propelled Grenades (RPGs)) launch events in the battlefield. OTHELLO hardware is described followed by an explanation of some inherent advantages of SWIR imagers as building blocks for optical detection systems mounted on ground military vehicles at harsh and demanding operating conditions. Finally we describe possible application of OTHELLO with radar systems.

A highly ruggedized infra-red sensor module has been developed which is suitable for a variety of fast framing applications in hostile fire detection and in scientific or industrial metrology. The sensor offers <1000fps in the full 384x384 format and useful images up to 6500fps in smaller formats. High operability for either mid-wave or long-wave IR applications is assured with high performance MOVPE fabrication technology. The paper reports design concepts and performance data for the MW variant.

SWIR cameras offer the advantage of higher resolution and smaller optical systems than conventional mid and far infrared optical systems. With the ability of seeing at low illumination conditions at the near infrared region, it can provide the detection of covert lasers. The ability of laser detection introduces the risk of sensor damage when the laser power is above a certain threat level. Smart protection is therefore needed, that is transparent for low laser intensities and limit or block the high laser intensities, and is effective over a wide band of wavelengths. We developed an Optical Power Control (OPC) device that reduces laser power threat to a safe level for a variety of optical systems. The talk presents a novel technology for protection of SWIR cameras against laser threats.

The thermal imager ATTICA was designed to fit into the thermal sights of the new German Infantry tank PUMA. The flexible approach for the optical concept, using different folding mirrors allows meeting the different available space requirements for thermal sights also of other tanks like the main battle tank Leopard 2 and the infantry fighting vehicle Marder. These tanks are going to be upgraded. The flexible concepts of the thermal imager optics as well as the mechanical packing solutions for the different space volumes of the commander and gunner sights of the vehicles are discussed.

Requirements for vehicle mounted infrared sensors, especially as imagers evolve to high definition (HD) format will be detailed and analyzed. Lessons learned from integrations of infrared sensors on armored vehicles, unarmored military vehicles and commercial automobiles will be discussed. Comparisons between sensors for driving and those for situation awareness, targeting and other functions will be presented. Conclusions will be drawn regarding future applications and installations. New business requirements for more advanced digital image processing algorithms in the sensor system will be discussed. Examples of these are smarter contrast/brightness adjustments algorithms, detail enhancement, intelligent blending (IR-Vis) modes, and augmented reality.

The paper introduces the analysis carried out by Selex ES (SE) for the development of a third generation IRST system based on large format MWIR sensors, separable in blue and red bands. In the feasibility study, physical constraints have been evaluated relying on different optics and scanning options. The goal is a system based on distributed heads to cover 360° with a resolution better than 0.3 mrad and high frame rate that allow to take advantage of the typical atmospheric phenomena of the maritime environment as scintillation and super and sub refraction. Two critical aspects were investigated: (i) the setting of an adequate scanning mechanism to assure a high frame rate and (ii) the stitching of the collected images while maintaining the bit-depth so as to avoid abrupt changes of SNR at the seams between two subsequent images.

Infrared sensor technology, high performance computing hardware and advanced detection and tracking algorithms have enabled a new generation of infrared warning systems for navy surface vessels. In this paper we describe Sea Spotter - a new third-generation naval IRST system, which is unique in offering a fully staring electro-optical imaging unit. Starting from naval IRST operational requirements, we describe the considerations and constraints that led us to the configuration of the sensor head and the supporting hardware. The second part of the paper is dedicated to the target acquisition methodology, including the use of originally developed machine learning technology for target acquisition and tracking.

Seven countries within the European Defence Agency (EDA) framework are joining effort in a four year project (2009-2013) on Detection in Urban scenario using Combined Airborne imaging Sensors (DUCAS). Data has been collected in a joint field trial including instrumentation for 3D mapping, hyperspectral and high resolution imagery together with in situ instrumentation for target, background and atmospheric characterization. Extensive analysis with respect to detection and classification has been performed. Progress in performance has been shown using combinations of hyperspectral and high spatial resolution sensors.

Based on a large experience, SOFRADIR is conducting major space programs covering all the wavelength range from visible to VLWIR as Sentinel projects in the frame of the GMES program or MTG detectors development and manufacturing for the future European meteorological satellites of third generation. In particular, new developments of MCT infrared detectors are currently made: • A new generation of SWIR hyperspectral detectors with a format of 1024x1024 / 15 µm pitch • Optimization of MCT performances for VLWIR spectral range aiming at new sounding missions • Developments of new infrared detectors for MTG program In this paper, a review of the main space programs conducted by SOFRADIR is presented with a particular emphasis on the last developments.

Vibration disturbances generated by cryocooler, representing in a series of harmonics, are critical issue in practical application. A control system including electronic circuit and mechanical actuator has been developed to attenuate the vibration. The control algorithm executes as a series of adaptive narrowband notch filters to reduce corresponding harmonics. The algorithm does not require actuator transfer function, thus ensure its adaptiveness. Using this algorithm, all the vibration harmonics of cryocooler were attenuated by a factor of more than 45.9 dB, i.e., the residual vibration force was reduced from 20.1Nrms to 0.102Nrms over the 300 Hz control bandwidth, the converging time is only less than 20 seconds, and the power consumption of mechanical actuator is less than half a watt. The vibration control system has achieved the general requirement of Infrared application.

The market of the sights for the 5.56 mm assault rifles is dominated by mainly three types of systems: TWS (Thermal Weapon Sight), the Pocket Scope with Weapon Mount and the Clip-on. The latter are designed primarily for special forces and snipers use, while the TWS design is triggered mainly by the DRI (Detection, Recognition, Identification) requirements. The Pocket Scope design is focused on respecting the SWaP (Size, Weight and Power dissipation) requirements. Compared to the TWS systems, for the last two years there was a significant technological growth of the Pocket Scope/Weapon Mount solutions, concentrated on the compression of the overall dimensions. The trend for the assault rifles is the use of small size/light weight (SWaP) IR sights, suitable mainly for close combat operations but also for extraordinary use as pocket scopes – handheld or helmet mounted. The latest developments made by Selex ES S.p.A. are responding precisely to the above-mentioned trend, through a miniaturized Day/Night sight embedding state-of-the art sensors and using standard protocols (USB 2.0, Bluetooth 4.0) for interfacing with PDAs, Wearable computers, etc., while maintaining the “shoot around the corner” capability. Indeed, inside the miniaturized Day/Night sight architecture, a wireless link using Bluetooth technology has been implemented to transmit the video streaming of the rifle sight to an helmet mounted display. The video of the rifle sight is transmitted only to the eye-piece of the soldier shouldering the rifle.

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 backbone computer. 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 adequate ranges. 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.

In late 2012 SSZ Camouflage Technology, AG, and Milliken and Company joined forces to bring apparel weight fabrics with infrared signature reduction to the US military, Homeland Security, and other law enforcement agencies. By significantly reducing the thermal infrared signature of soldiers wearing these fabrics, this technology goes beyond the current visual and near infrared range (NIR) to provide concealment in the mid wave infrared range (MWIR) and long wave infrared range (LWIR) thus reducing the risk of detection from thermal infrared imagers. This infrared camouflage technology can be incorporated into a variety of performance fabrics which can provide U.S. Military, Homeland Security, and law enforcement personnel with better concealment, adding yet another layer of protection to their uniforms.n late 2012 SSZ Camouflage Technology, AG, and Milliken and Company joined forces to bring apparel weight fabrics with

Further reduction of size, weight and power consumption of the High Operating Temperature (HOT) infrared (IR) Integrated Detector-Dewar-Cooler Assemblies (IDDCA) eventually calls for development of high-speed cryocoolers. In case of integral rotary design, the immediate penalty is the more intensive slapping of compression and expansion pistons along with intensification of micro collisions inherent for the operation of crank-slide linkages featuring ball bearings. Resulting from this is the generation of impulsive vibration export, the spectrum of which features the driving frequency along with numerous multiples covering the entire range of audible frequencies. In a typical design of an infrared imager, the metal light-weight enclosure accommodates a directly mounted IDDCA and an optical train, thus serving as an optical bench and heat sink. This usually results in excitation of structural resonances in the said enclosure and, therefore, in excessive noise generation compromising the aural stealth. The author presents the complex approach to a design of aural undetectable infrared imagers in which the IDDCA is mounted upon the imager enclosure through a silent pad. Special attention is paid to resolving the line of sight stability and heat sinking issues. The demonstration imager relying on Ricor K562S based IDDCA meets the most stringent requirement to 10 meters aural non-detectability distance (per MIL-STD 1474D, Level II) even during boost cooldown phase of operation.

We report a bias selectable dual-band mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector’s electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature’s 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective.

Poor passivation on photodetectors can result in catastrophic failure of the device. Abrupt termination of mesa side walls during pixel definition generates dangling bonds that lead to inversion layers and surface traps leading to surface leakage currents that short circuit diode action. Good passivation, therefore, is critical in the fabrication of high performance devices. Silicondioxide has been the main stay of passivation for commercial photodetectors, deposited at high temperatures and high RF powers using plasma deposition techniques. In photodetectors based on III-V compounds, sulphur passivation has been shown to replace oxygen and saturate the dangling bonds. Despite its effectiveness, it degrades over time. More effort is required to create passivation layers which eliminate surface leakage current. In this work, we propose the use of sulphur based octadecanethiol (ODT), CH₃(CH₂)₁₇SH, as a passivation layer for the InAs/GaSb superlattice photodetectors that acts as a self assembled monolayer (SAM). ODT SAMs consist of a chain of 18 carbon atoms with a sulphur atom at its head. ODT Thiol coating is a simple process that consist of dipping the sample into the solution for a prescribed time. Excellent electrical performance of diodes tested confirm the effectiveness of the sulphur head stabilized by the intermolecular interaction due to van der Walls forces between the long chains of ODT SAM which results in highly stable ultrathin hydrocarbon layers without long term degradation.

To examine defects in InAs/GaSb type-II superlattices we investigated GaSb substrates and epitaxial InAs/GaSb layers by synchrotron white beam X-ray topography to characterize the distribution of threading dislocations. Those measurements are compared with wet chemical etch pit density measurements on GaSb substrates and InAs/GaSb type-II superlattices epitaxial layer structures. The technique uses a wet chemical etch process to decorate threading dislocations and an automated optical analyzing system for mapping the defect distribution. Dark current and noise measurements on processed InAs/GaSb type-II superlattice single element photo diodes reveal a generation-recombination limited dark current behavior without contributions by surface leakage currents for midwavelength infrared detectors. In the white noise part of the noise spectrum, the extracted diode noise closely matches the theoretically expected shot noise behavior. For diodes with an increased dark current in comparison to the dark current of generation-recombination limited material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre’s noise model for avalanche multiplication processes fits the data quite well. We suggest that within high electric field domains localized around crystallographic defects, electrons initiate avalanche multiplication processes leading to increased dark current and excess noise.

Time-resolved photoluminescence (TRPL) is used to study the minority carrier lifetime in type-II superlattice (T2SL) infrared detector materials to investigate the recombination mechanisms, trap states and transport properties that currently limit their performance. Measurements of carrier lifetime have shown that InAs/Ga_1-xIn_xSb T2SLs are dominated by non-radiative Shockley-Read-Hall (SRH) recombination, resulting in short minority carrier lifetimes (10’s of nanoseconds at 77 K). A trap energy of ~60 meV above the valence band is identified in mid-wavelength infrared n-type InAs/Ga_1-xIn_xSb T2SLs, where trap saturation (non-exponential decay) is observed under high injection levels due to a significantly faster hole capture rate than electron capture rate. Lifetime measurements in “Ga-free” InAs/InAs_1-xSb_x T2SLs exhibit an order-of-magnitude increase in lifetime (100’s of nanoseconds at 77 K) with contributions from both radiative and non-radiative recombination. This improvement is attributed to the reduction of non-radiative recombination centers from the superlattice with the elimination of Ga and suggests that the SRH trap(s) limiting the carrier lifetime of InAs/Ga_1-xIn_xSb T2SLs is native to the Ga_1-xIn_xSb layer. Additionally, radiative recombination is observed in an InAs/GaSb T2SL using a sub-bandgap CW laser to saturate the SRH recombination centers, yielding a radiative lifetime of ~140 ns at 77 K. Since carrier transport is a concern in Ga-free T2SLs, it is investigated by studying samples grown with and without barriers (to contain injected carriers to the absorber region). It is determined that carrier transport is poor in InAs/InAs_1-xSb_x T2SLs because negligible differences are observed in the carrier lifetime.

We describe a relationship between the noise characterization and activation energy of InAs/GaSb superlattice Mid-Wavelength-Infrared photodiodes for different passivation materials applied to the device. The noise measurements exhibited a frequency dependent plateau (i.e. 1/f-noise characteristic) for unpassivated as well as Si₃N₄ passivated samples whereas 1/f-type low noise suppression (i.e. frequency independent plateau) with a noise current reduction of more than one order of magnitude was observed for SiO₂ passivation. For reverse bias values below -0.15V, the classical Schottky-noise calculation alone did not appear to describe the noise mechanism in a SL noise behavior, which shows a divergence between theoretically and experimentally determined noise values. We identify that, the additional noise appears, with and without passivation, at the surface activation energy of < 60 meV and is inversely proportional to the reverse bias. This is believed to be caused by the surface dangling-bonds (as well as surface states) whose response is controlled by the applied reverse bias. The calculated noise characteristics showed a good agreement with the experimental data.

A VGA format type-II superlattice focal plane array (FPA) for the mid-wave infrared (MWIR) atmospheric window has been designed, manufactured and characterized. The detector material is based on a heterojunction structure with a barrier that effectively decreases the Shockley-Read-Hall based component of the dark current. A very effective passivation method has been used which successfully inhibits all surface leakage currents. The barrier structure has a 50 % cutoff at 5 µm and 65 % quantum efficiency without antireflective coating. The dark current density is 3×10^-6 A/cm² at -0.05 V bias and 120 K. The optical cavity of the detector has been optimized for maximum capture of available light in the MWIR window. A focal plane array with 640 by 512 pixels and 15 µm pitch was processed based on this barrier structure. High-quality imagery in a system with high F-number will be presented.

Bulk unrelaxed InAsSb alloys with Sb compositions up to 44 % and layer thicknesses up to 3 µm were grown by molecular beam epitaxy. The alloys showed photoluminescence (PL) energies as low as 0.12 eV at T = 13 K. The electroluminescence and quantum efficiency data demonstrated with unoptimized barrier heterostructures at T= 80 and 150 K suggested large absorption and carrier lifetimes sufficient for the development of long wave infrared detectors and emitters with high quantum efficiency. The minority hole transport was found to be adequate for development of the detectors and emitters with large active layer thickness.

Bulk 4" GaSb crystal growth methods based on the Czochralski technique are detailed which deliver highly mono-crystalline substrates that are characterized by low dislocation densities. The latest developments in epitaxy-ready surface finishing will be described and results presented for 4” GaSb substrates processed on a large format, commercial multiwafer polishing platform. Bulk material quality assessments will be made and the surface condition of bare substrates and epitaxial material grown on top of 4" GaSb substrates will be assessed by various surface analytical techniques. We will comment on the available production capacity for 4" GaSb and remark on the scaling challenges that will be required to support the anticipated increase in demand for large diameter GaSb substrates.

The GaSb-based family of materials and heterostructures provides rich bandgap engineering possibilities for a variety of infrared (IR) applications. Mid-wave and long-wave IR photodetectors are progressing toward commercial manufacturing applications, but to succeed they must move from research laboratory settings to general semiconductor production and they require larger diameter substrates than the current standard 2-inch and 3-inch GaSb. Substrate vendors are beginning production of 4-inch GaSb, but another alternative is growth on 6-inch GaAs substrates with appropriate metamorphic buffer layers. We have grown generic MWIR nBn photodetectors on large diameter, 6-inch GaAs substrates by molecular beam epitaxy. Multiple metamorphic buffer architectures, including bulk GaSb nucleation, AlAsSb superlattices, and graded GaAsSb and InAlSb ternary alloys, were employed to bridge the 7.8% mismatch gap from the GaAs substrates to the GaSb-based epilayers at 6.1 Å lattice-constant and beyond. Reaching ~6.2 Å extends the nBn cutoff wavelength from 4.2 to <5 µm, thus broadening the application space. The metamorphic nBn epiwafers demonstrated unique surface morphologies and crystal properties, as revealed by AFM, high-resolution XRD, and cross-section TEM. GaSb nucleation resulted in island-like surface morphology while graded ternary buffers resulted in cross-hatched surface morphology, with low root-mean-square roughness values of ~10 Å obtained. XRD determined dislocation densities as low as 2 × 10⁷ cm^-2. Device mesas were fabricated and dark currents of 1 × 10^-6 A/cm² at 150K were measured. This work demonstrates a promising path to satisfy the increasing demand for even larger area focal plane array detectors in a commercial production environment.

We report ternary growth studies to develop a largely strained InAs/InGaSb superlattice (SL) material for very long wavelength infrared (VLWIR) detection. We select a SL structure of 47.0 Å InAs/21.5 Å In_0.25Ga_0.75Sb that theoretically designed for the greatest possible detectivity, and tune growth conditions for the best possible material quality. Since material quality of grown SLs is largely influenced by extrinsic defects such as nonradiative recombination centers and residual background dopings in the grown layers, we investigate the effect of growth temperature (T_g) on the spectral responses and charge carrier transports using photoconductivity and temperature-dependent Hall effect measurements. Results indicate that molecular beam epitaxy (MBE) growth process we developed produces a consistent gap near 50 meV within a range of few meV, but SL spectral sensing determined by photoresponse (PR) intensity is very sensitive to the minor changes in T_g. For the SLs grown from 390 to 470 °C, a PR signal gradually increases as T_g increases from 400 to 440 °C by reaching a maximum at 440 °C. Outside this growth window, the SL quality deteriorates very rapidly. All SLs grown for this study were n-type, but the mobility varied in a variety of range between 11,300 and 21 cm²/Vs. The mobility of the SL grown at 440 °C was approximately 10,000 V/cm² with a sheet carrier concentration of 5 × 10¹¹ cm^-2, but the mobility precipitously dropped to 21 cm²/Vs at higher temperatures. Using the knowledge we learned from this growth set, other growth parameters for the MBE ternary SL growth should be further adjusted in order to achieve high performance of InAs/InGaSb materials suitable for VLWIR detection.

We report on the development of InAs/AlSb/GaSb based N-structure superlattice pin photodiode. In this new design, AlSb layer in between InAs and GaSb layers acts as an electron barrier that pushes electron and hole wave functions towards the GaSb/InAs interface to perform strong overlap under reverse bias. Experimental results show that, with only 20 periods of intrinsic layers, dark current density and dynamic resistance at -50 mV bias are measured as 6x10^-3 A/cm² and 148 Ωcm² at 77K, respectively. Under zero bias, high spectral response of 1.2A/W is obtained at 5 μm with 50% cut-off wavelengths (λ_c) of 6 μm. With this new design, devices with only 146 nm thick i-regions exhibit a quantum efficiency of 42% at 3 μm with front-side illimunation and no anti-reflection coatings.

This paper describes our efforts on the development of low dark current long-wave infrared (LWIR) photodetectors based on type-II InAs/GaSb strained superlattices. By adopting a so-called pBiBn structure, a hybrid between the conventional PIN structure and unipolar barrier concepts, suppressed dark current and near-zero-bias operation are obtained, respectively. The LWIR photodetector has a dark current density as low as 1.42×10^-5 A/cm² at -60 mV, and R₀A of 5365 Ωcm² at 76 K. The measured peak detectivity at 10.2 µm of 8.7×10¹⁰ cmHz^1/2W^-1 is obtained at -60 mV at 76 K. To further improve the device performances, a newer design with longer cut-off wavelength targeted for near zero-bias was also realized. This 2-µm-thick device exhibits a quantum efficiency of 20% at 10 µm under zero-bias.

We present the development status of Type II superlattice (T2SL) infrared detector in JAXA. Since 2009, we have started a basic research on InAs/GaSb T2SL infrared detectors. Our final goal is to realize the T2SL array detector having a cutoff wave length of λc=15 μm. In order to confirm a technical feasibility of 15 μm cutoff T2SL detector, we fabricated T2SL samples having a different thickness of InAs/ 7 monolayers (ML) GaSb. These crystals are designed for the cutoff wavelength from 6 μm to 15 μm. The X-ray Diffraction measurement shows a mismatch between the substrate and superlattice layers is below 0.006%. The surface morphology of the samples with an atomic force microscope is 1.5-3.3 Å RMS for 5×5 μm square regions. We also fabricated single pixel detectors with these crystals. We show the results of the spectral response measurement using a FTIR system. We also show the development status of an array detector. The array detector having the cutoff wavelength of 6 μm is successfully demonstrated. However, further improvements are required for a future 15 μm cutoff array detector.

A wavelength selective wideband uncooled infrared (IR) sensor that detects middle-wavelength and long-wavelength infrared (MWIR and LWIR) regions has been developed using a two-dimensional plasmonic absorber (2D PLA). The 2D PLA has a Au-based 2D periodic hole-array structure, where photons can be manipulated using the surface plasmonlike mode. Numerical investigations demonstrate that the wavelength of the absorption can be designed according to the surface period of holes over a wide wavelength range (MWIR and LWIR regions). A microelectromechanical system (MEMS)-based uncooled IR sensor with a 2D PLA was fabricated using complementary metal oxide semiconductor (CMOS) and micromachining techniques. The 2D PLA was formed from a Au layer sputtered on a perforated oxide layer. A reflection layer was introduced to the backside of the 2D PLA to prevent additional absorption. Measurement of the spectral responsivity shows that selective enhancement of responsivity is achieved over both MWIR and LWIR regions, where the wavelength of the responsivity peak coincides with the hole period of the 2D PLA. The results obtained here provide direct evidence that a wideband wavelength selective IR sensor can be realized simply by design of the 2D PLA surface structure without the need for vertical control in terms of gap or thickness. A pixel array where each pixel has a different detection wavelength would be developed for multicolor infrared imaging using standard CMOS and micromachining techniques.

A dual-band microbolometer with separate absorption of each wavelength band would be desirable for multispectral applications. In addition, a three dimensional (3D) stacked structure would be advantageous for size and integration in focal plane arrays. We present designs for a 3D stacked dual-band microbolometer based on the in-band and out-of-band reflection and transmission characteristics of resistive dipoles and slots. The mechanism of individual absorption in each layer of a dual-band microbolometer is analyzed and simulated to allow the resistive slot layer to efficiently absorb the LWIR band while a superposed resistive dipole layer absorbs the MWIR band. The top dipole layer is designed to have peak absorption at 5 μm, with a second underlying slot layer and mirror layer designed to have peak absorption at 10 μm. The stacked combination of two different types of layers provides highly efficient wavelength selective absorption, yielding calculated power absorption efficiency of nearly 100 % for both LWIR and MWIR bands.

An uncooled microbolometer with peak responsivity in the long wave infrared region of the electromagnetic radiation is developed at Sensonor AS. It is a 384 x 288 focal plane array with a pixel pitch of 25µm, based on monocrystalline Si/SiGe quantum wells as IR sensitive material. The high sensitivity (TCR) and low 1/f-noise are the main performance characteristics of the product. The frame rate is maximum 60Hz and the output interface is digital (LVDS). The quantum well thermistor material is transferred to the read-out integrated circuit (ROIC) by direct wafer bonding. The ROIC wafer containing the released pixels is bonded in vacuum with a silicon cap wafer, providing hermetic encapsulation at low cost. The resulting wafer stack is mounted in a standard ceramic package. In this paper the architecture of the pixels and the ROIC, the wafer packaging and the electro-optical measurement results are presented.

Metal-Oxide-Metal diodes offer the possibility of directly rectifying infrared radiation. To be effective for sensing or energy harvesting they must be coupled to an antenna which produces intense fields at the diode. While antennas significantly increase the effective capture area of the MOM diode, it is still limited and maximizing the captured energy is still a challenging goal. In this work we investigate integrating MOM diodes with a slot antenna Frequency Selective Surface (FSS). This maximizes the electromagnetic capture area while minimizing the transmission line length which helps reduce losses because metal losses are much lower at DC than at infrared frequencies. Our design takes advantage of a single self-aligned patterning step using shadow evaporation. The structure is optimized at 10.6 µm to have less than 2% reflection (polarization sensitive) and simulations predict that 70% of the incident energy is dissipated into the oxide layer. Initial experimental results fabricated with e-beam lithography are presented and the diode coupled FSS is shown to produce a polarization sensitive unbiased DC short circuit current. This work is promising for both infrared sensing and imaging as well as direct conversion of thermal energy.

We experimentally demonstrate a structured thin film that selectively absorbs incident electromagnetic waves in discrete bands, which by design occur in any chosen range from near UV to far infrared. The structure consists of conducting islands separated from a conducting plane by a dielectric layer. By changing dimensions and materials, we have achieved broad absorption resonances centered at 0.36, 1.1, 14, and 53 microns wavelength. Angle-dependent specular reflectivity spectra are measured using UV-visible or Fourier spectrometers. The peak absorption ranges from 85 to 98%. The absorption resonances are explained using the model of an LCR resonant circuit created by coupling between dipolar plasma resonance in the surface structures and their image dipoles in the ground plane. The resonance wavelength is proportional to the dielectric permittivity and to the linear dimension of the surface structures. These absorbers have application to thermal detectors of electromagnetic radiation.

This paper introduces a method of broadband absorption enhancement that can be integrated with the conventional suspended microbolometer process with no significant additional cost. The premise of this study is that electric field can be enhanced throughout the structural layer of the microbolometer, resulting in an increase in the absorption of the infrared radiation in the long wave infrared window. A concentric double C-shaped plasmonic geometry is simulated using the FDTD method, and this geometry is fabricated on suspended pixel arrays. Simulation results and FTIR measurements are in good agreement indicating a broadband absorption enhancement in the 8 µm-12 µm range for LWIR applications. The enhancement is attained using metallic geometries embedded in the structural layer of the suspended microbridge, where the metallic-dielectric interface increases the average absorption of a 35 µm pixel from 67.6% to 80.1%.

During his distinguished 37-year career as a research physicist at the Honeywell Research Center in Minneapolis, Minnesota, Dr. Paul W. Kruse (1927-2012) played leadership roles in two disruptive infrared detector technologies, the narrow-gap semiconductor alloy HgCdTe and the silicon CMOS-based microbolometer array, both of which revolutionized the worldwide infrared detector industry. He served on numerous government advisory boards and panels, including the Army Scientific Advisory Panel and the Army Science Board, for which he received the Outstanding Civilian Service Medal. After retiring for Honeywell in 1993, he remained active in the infrared detector field in several roles: as a successful small-business entrepreneur, as an author of two books, and as a SPIE lecturer. His books, papers and lectures have educated new generations of workers in the infrared detector industry. His career, a model for industrial research physicists, has had major and permanent impacts on the worldwide infrared detector industry. This paper is a summary of the career of Paul W. Kruse, as well as a tribute to that career and its lasting legacy.

Uncooled infrared detectors with 12μm pixel pitch video graphics array (VGA) have been developed. To improve the signal to noise ratio (SNR) for 12μm pixel pitch, a highly sensitive bolometer material, an advanced pixel structure for thermal isolation and a newly designed read-out IC (ROIC) have been also developed. The bolometer material has been improved by using vanadium niobate. Over a wide range of temperature, temperature coefficient of resistance (TCR) is achieved higher level than -3.6%/K, which is 2 times higher than that for the conventional bolometer material. For thermal isolation, thermal conductance (Gth) value for the new pixel structure, fabricated by using triple level sacrificial layer process, is estimated to be 5nW/K, which is 1/5 times lower than that for the conventional pixel structure. On the other hand, since the imaging area is reduced by the pixel pitch, the uniformity of pixel can be improved. This enables to remove the non-uniformity correction (NUC) circuit in the ROIC. Removal of this circuit is effective for low power and low noise. This 12μm pixel pitch VGA detector is packaged in a compact (24 × 24 × 6.5 mm) and lightweight (11g) ceramic package. In addition, it has been incorporated in a newly developed prototype miniature imager. The miniature imager has dimension of 25(H) ×25(W) ×28(L) mm and weight of 30g. This imager is compact and small enough to fit in your hand. Hereafter, this imager is greatly expected to be applied to mobile systems.

Long range sights and targeting systems require a combination of high spatial resolution, low temporal NETD, and wide field of view. For practical electro-optical systems it is hard to support these constraints simultaneously. Moreover, achieving these needs with the relatively low-cost Uncooled μ-Bolometer technology is a major challenge in the design and implementation of both the bolometer pixel and the Readout Integrated Circuit (ROIC). In this work we present measured results from a new, large format (1024×768) detector array, with 17μm pitch. This detector meets the demands of a typical armored vehicle sight with its high resolution and large format, together with low NETD of better than 35mK (at F/1, 30Hz). We estimate a Recognition Range for a NATO target of better than 4 km at all relevant atmospheric conditions, which is better than standard 2nd generation scanning array cooled detector. A new design of the detector package enables improved stability of the Non-Uniformity Correction (NUC) to environmental temperature drifts.

We have developed a low-cost uncooled infrared radiation focal plane array (FPA) requiring no thermoelectric cooler (TEC), which has 320 x 240 detection pixels with 22 um pitch. The silicon single-crystal series p-n junction diodes and the low-noise readout circuit on the same SOI wafer fabricated by 0.13 um CMOS technology were utilized for infrared (IR) detection. The temperature dependence in the readout circuit was eliminated by correlated double sampling (CDS) operation with reference pixel that was insensitive to infrared radiation. In order to reduce the temperature dependence, we improved the reference pixel and the readout circuit. Although the reference pixels should be completely insensitive to IR radiation, prior reference pixels showed measurable sensitivity. The improved reference pixel was formed by partially releasing with bulk-micromachining and was verified to be insensitive to IR radiation by an object of 400°C. The readout circuit had a differential amplifier instead of a singletransistor amplifier and an analog-to-digital converter (ADC). In each portion, CDS was applied to reduce temperature dependence. The first CDS operation was used for eliminating the pixel output variation and the second operation was used for canceling the variation of the differential amplifier. The output variation referred to input was reduced to 1/30 compared with that of the prior circuit. Moreover, the residual variation of output voltage was reduced by CDS operation in ADC and stable output data was obtained with ambient temperature variation. With these improvements, the sensitivity variation of the FPA was improved to 10% in the range of -30 degrees to 80 degrees and noise equivalent temperature difference (NETD) of 40 mK was achieved.

Seventeen (17) µm pixel Long Wave Infrared (LWIR) Sensors based on vanadium oxide (VO_x) micro-bolometers have been in full rate production at BAE Systems’ Night Vision Sensors facility in Lexington, MA for the past five years.[1] We introduce here a commercial camera core product, the Airia-M^TM imaging module, in a VGA format that reads out in 30 and 60Hz progressive modes. The camera core is architected to conserve power with all digital interfaces from the readout integrated circuit through video output. The architecture enables a variety of input/output interfaces including Camera Link, USB 2.0, micro-display drivers and optional RS-170 analog output supporting legacy systems. The modular board architecture of the electronics facilitates hardware upgrades allow us to capitalize on the latest high performance low power electronics developed for the mobile phones. Software and firmware is field upgradeable through a USB 2.0 port. The USB port also gives users access to up to 100 digitally stored (lossless) images.

The DRS Tamarisk® ₃₂₀ camera, introduced in 2011, is a low cost commercial camera based on the 17 µm pixel pitch 320×240 VOx microbolometer technology. A higher resolution 17 µm pixel pitch 640×480 Tamarisk®₆₄₀ has also been developed and is now in production serving the commercial markets. Recently, under the DARPA sponsored Low Cost Thermal Imager-Manufacturing (LCTI-M) program and internal project, DRS is leading a team of industrial experts from FiveFocal, RTI International and MEMSCAP to develop a small form factor uncooled infrared camera for the military and commercial markets. The objective of the DARPA LCTI-M program is to develop a low SWaP camera (<3.5 cm³ in volume and <500 mW in power consumption) that costs less than US $500 based on a 10,000 units per month production rate. To meet this challenge, DRS is developing several innovative technologies including a small pixel pitch 640×512 VOx uncooled detector, an advanced digital ROIC and low power miniature camera electronics. In addition, DRS and its partners are developing innovative manufacturing processes to reduce production cycle time and costs including wafer scale optic and vacuum packaging manufacturing and a 3-dimensional integrated camera assembly. This paper provides an overview of the DRS Tamarisk® project and LCTI-M related uncooled technology development activities. Highlights of recent progress and challenges will also be discussed. It should be noted that BAE Systems and Raytheon Vision Systems are also participants of the DARPA LCTI-M program.

In this work a breakthrough in the field of low cost uncooled infrared detectors is presented: an 80x80 MWIR VPD PbSe detector monolithically integrated with the corresponding Si-CMOS circuitry. Fast speed of response and high frame rates are, until date, non existing performances in the domain of low cost uncooled IR imagers. The new detector presented fills the gap. The device is capable to provide MWIR images to rates as high as 2 KHz, full frame, in real uncooled operation which converts it in an excellent solution for being used in applications where short events and fast transients dominate the system dynamics to be studied or detected. VPD PbSe technology is unique because combines all the main requirements demanded for a volume ready technology: 1. Simple processing 2. Good reproducibility and homogeneity 3. Processing compatible with big areas substrates 4. Si-CMOS compatible (no hybridation needed) 5. Low cost optics and packagin The new FPA represents a milestone in the road towards affordable uncooled MWIR imagers and it is the demonstration of VPD PbSe technology has reached industrial maturity. The device presented in the work was processed on 8-inch Si wafers with excellent results in terms of manufacturing yield and repeatability. The technology opens the MWIR band to SWaP concept.

Penetration of uncooled (room temperature operation) thermal detector arrays into high volume commercial products depends on very low cost technology linked to high volume production. A series of innovative and revolutionary developments is now allowing arrays based on bulk pyroelectric ceramic material to enter the consumer marketplace providing everything from sophisticated security and people monitoring devices to hand held thermal imagers and visual IR thermometers for preventative maintenance and building inspection. Although uncooled resistive microbolometer detector technology has captured market share in higher cost thermal imager products we describe a pyroelectric ceramic technology which does not need micro electro-mechanical systems (MEMS) technology and vacuum packaging to give good performance. This is a breakthrough for very low cost sensors and imagers. Recent developments in a variety of products based on pyroelectric ceramic arrays are described and their performance and applicability compared and contrasted with competing technologies.

This paper presents a 32x32 microbolometer thermal imaging sensor for human body temperature measurement. Waferlevel vacuum packaging technology allows us to get a low cost and compact imaging sensor chip. The microbolometer uses V-W-O film as sensing material and ROIC has been designed 0.35-um CMOS process in UMC. A thermal image of a human face and a hand using f/1 lens convinces that it has a potential of human body temperature for commercial use.

Nickel oxide (NiO) film was formed on the SiO₂/Si substrate at the room temperature with water cooling system by reactive RF sputter. The feasibility of bolometric material was investigated, and a microbolometer using the NiO film was fabricated and evaluated. The NiO films were analyzed by using grazing-incidence X-ray diffraction (GIXRD). The NiO(111), NiO (200), and NiO (220) peaks expected as the main spectrum were dominantly appeared on the polycrystalline NiO films. The representative resistivity acquired at the O₂/(Ar+O₂) ratio of 10% sample was about 40.6 Ωcm. The resistivity of 40.6 Ωcm obtained in low oxygen partial pressure was inclined to reduce to 18.65 Ωcm according to the increase of the O₂/(Ar+O₂) ratio. The TCR value of fabricated microbolometer was −1.67%/℃ at the NiO film resistivity of 40.6 Ωcm. The characteristics of fabricated NiO film and microbolometer were demonstrated by XRD patterns, TCR value, and SEM image.

This paper presents a systematic study of the 1/f noise coefficient as a function of pixel geometry for microbolometer structures. Structures with various VO_x widths, electrode gaps, electrode widths and via hole sizes were fabricated and characterized. The experimental results show that the 1/f noise coefficient is adversely affected by current non uniformity, in agreement with model predictions. Design parameters that significantly impact current non uniformity are identified and approaches to minimize their importance are proposed.

Presented is an uncooled surface-micromachined thermoelectric (TE) infrared detector that features P-doped and N-doped polysilicon wires as the thermocouple pair and an umbrella like optical cavity as the absorber to achieve a high fill factor. A responsivity as high as1800V/W @5Hz and a response time of smaller than ~10ms are measured in vacuum when viewing a 500K blackbody with no concentrating optics at room temperature. The reported responsivity is more than 10 times higher than the value reported earlier [1] from similar structures due to the improvement in the thermoelectric coefficient and the thermal isolation of the cell. Finite Element Analysis is used to predict the detector’s performance and the results are in a good agreement with the measurements. The dominant source of noise is also investigated in these thermoelectric IR detectors and it is believed to be Johnson noise when they are operated under an open circuit condition. The fabricated detectors have resistances in the range of 20 to 70KOhm resulting in a Johnson noise of about 20 to 36 nV/Hz^0.5. The specific detectivity (D*) is calculated to be higher than 10^8cmHz^0.5/W. To the best of our knowledge, this is the highest reported D* for such small thermoelectric IR sensors. The measured NETD is 120mK with an f/1.5 lens.

Over the past few years, a new type of High Operating Temperature (HOT) photon detector has been developed at SCD, which operates in the blue part of the MWIR window of the atmosphere (3.4-4.2 μm). This window is generally more transparent than the red part of the MWIR window (4.4-4.9 μm), especially for mid and long range applications. The detector has an InAsSb active layer, and is based on the new "XBn" device concept. We have analyzed various electrooptical systems at different atmospheric temperatures, based on XBn-InAsSb operating at 150K and epi-InSb at 95K, respectively, and find that the typical recognition ranges of both detector technologies are similar. Therefore, for very many applications there is no disadvantage to using XBn-InAsSb instead of InSb. On the other hand XBn technology confers many advantages, particularly in low Size, Weight and Power (SWaP) and in the high reliability of the cooler and Integrated Detector Cooler Assembly (IDCA). In this work we present a new IDCA, designed for 150K operatio