This paper describes the status of MCT IR technology in France at Leti and Sofradir. This concerns first evolution of crystal growth of large CZT for substrates, and MCT epilayers grown by LPE and MBE. A focus will be made on extrinsic doping of MCT with Indium and Arsenic for device fabrication. Evolution of detector technology will also be considered for detectors that operate from NIR/SWIR to VLWIR, moving from an n on p vacancy doped technology to a fully extrinsically doped p on n device architecture. Last results on 3(rd) generation detectors such as multicolor FPAs, HOT detectors and 2D or 3D FPAs that use MCT APD will also be described. Moving to larger FPAs, pixel pitch reduction become mandatory and technology evolution to achieve this goal will be presented. Then, cost reduction achievement through more compact systems that operate at higher temperature and/or integrate optical functions inside the cryostat will also be considered.

HgCdTe (Mercury Cadmium Telluride / MCT) staring arrays for infrared detection do show constant improvements regarding their compactness and performances.Among the new detectors, the family of 15 mu m pixel pitch detectors is offering a mid-TV format (384 x 288), a TV format (640 x 512) and a HD-TV format (1280 x 1024). Each detector is available in a SWaP configuration (meaning dedicated to applications requiring low Size, Weight and Power)Thanks to recent improvements and new technological breakthrough, the MCT technology allows operating detectors at higher temperature, in order to save power consumption at system level. In parallel, the 15 mu m pitch permits to reach challenging density and spatial resolution. These Focal Plane Arrays (FPA) are proposed in different tactical dewars, corresponding to various systems solutions.

This paper presents an overview of the very recent developments of the MCT infrared detector technology developed by CEA-LETI and Sofradir in France. New applications require high sensitivity, higher operating temperature and dual band detectors. The standard n on p technology in production at Sofradir for 25 years is well mastered with an extremely robust and reliable process. Sofradir's interest in p on n technology opens the perspective of reducing dark current of diodes so detectors could operate in lower flux or higher operating temperature. In parallel, MCT Avalanche Photo Diodes (APD) have demonstrated ideal performances for low flux and high speed application like laser gated imaging during the last few years. This technology also opens new prospects on next generation of imaging detectors for compact, low flux and low power applications. Regarding 3rd Gen IR detectors, the development of dual-band infrared detectors has been the core of intense research and technological improvements for the last ten years. New TV (640 x 512 pixels) format MWIR/LWIR detectors on 20μm pixel pitch, made from Molecular Beam Epitaxy, has been developed with dedicated Read-Out Integrated Circuit (ROIC) for real simultaneous detection and maximum SNR. Technological and products achievements, as well as latest results and performances are presented outlining the availability of p/n, avalanche photodiodes and dual band technologies for new applications at system level.

Cooled IR technologies are challenged for answering new system needs like the reduction of energy. This reduction is requested in new IR system design in particular for cooled IR detection. The goal is to reduce system sizes, to increase system autonomies and reliabilities and globally to reduce system costs! One of the key drivers for cooled systems is the cooler and the operating temperature. As far as operating temperature is concerned, Sofradir put a lot of efforts for years for adapting its technologies to increase the operating temperatures of IR detectors. Main examples are dealing with long wave staring arrays based on QWIP technology and on MCT technology as well as medium wave staring arrays using MCT technologies.

Low IR input flux conditions are answering different system applications as gas detection needs, active imagery, very long ranges detection and identification and some scientific applications. Then for other applications like ground applications, some system design trade-off could be made between thermal performance and identification and equipment size and cost.

More and more systems are requested to be more compact keeping constant system performances. One of the best approach is to reduce the pixel pitch of the IR detector while new technology improvements are carried out to improve the detector performance.The last developments at SOFRADIR / France for cooled IR detectors are following these trends. As a matter of fact, HgCdTe (Mercury Cadmium Telluride / MCT) staring arrays for infrared detection do show constant improvements regarding their compactness, by reducing the pixel pitch, and regarding performances.Among the new detectors, the family of 15 mu m pixel pitch detectors is offering a mid-TV format (384 x 288), a TV format (640 x 512) and a HD-TV format (1280 x 1024). The latest development concerning the mid-TV format is performed according to very challenging specifications regarding compactness and low power consumption. Thanks to recent improvements, the MCT technology allows to operate detectors at higher temperature (HOT detectors), in order to save power consumption at system level. In parallel, the 15 mu m pitch permits to reach challenging density and spatial resolution. This Focal Plane Arrays (FPA) is proposed in different tactical dewars, corresponding to various systems solutions.

France has a long and fruitful history regarding Mercury Cadmium Telluride (MCT) research and production and is still one of the leading countries for the production of MCT IR detectors. To give a historical account of its development and progress, SAGEM Défense Sécurité will describe the early days of MCT developments in France. CEA-Leti (the French Atomic Energy Commission and a leading applied research center in electronics) will then present the research carried out on second- and third-generation MCT technologies, followed by Sofradir who will discuss the production of these new detector types.

Sofradir IR detectors are being deployed in a lengthening line of space applications (earth observation, atmospheric observation, scientific missions, etc...). At first glance, one may ask what do detectors for space applications have in common with detectors for tactical applications? On the one hand, space applications require far fewer quantities and IR detector reliability and electro-optical performances must be exceptionally high. Tactical applications, on the other hand, look to quantities in the thousands per year, delivered at low cost. As opposed to focusing on the differences, Sofradir is taking advantage of these two areas. Firstly, space applications are developing new advances and technologies that can later be introduced in the production of IR detectors for tactical applications, thereby increasing their quality and reliability. In addition, Sofradir can better satisfy space application requirements for failure rates, as these can only be demonstrated with the large number of detectors manufactured, which tactical applications provide. This advantage is only possible because the core of the technologies and manufacturing processes are common to both applications. As a result, this approach offers a continuous cycle for reliability of IR detectors, accelerating reliability growth in production, and at the same time meeting requirements for space applications.

New applications require high sensitivity infrared (IR) sensors in order to detect very low incident fluxes. Laser gated imaging has, in particular, additional specific needs. IR sensors for this type of application are synchronized with eye-safe lasers, and have to detect a weak signal backscattered from the target on the order of 10 photons per pulse. They also have to be able to operate with a very short integration time, typically one hundred nanoseconds, to gate the backscattered signal around the target. In partnership with Sofradir, CEA/LETI (France) has developed high quality HgCdTe avalanche photodiodes satisfying these requirements. In parallel, specific studies have been carried out at the Read-Out Circuit level to develop optimized architectures. Thanks to these advances, a new Integrated Dewar Detector Cooler Assembly has been developed. This new product is the first step in a road-map to address low flux infrared sensors in the next few years.

We report the latest developments of MW HgCdTe electron initiated avalanche photo-diodes (e-APDs) focal plane arrays (FPAs) at CEA-LETI. The MW e-APD FPAs are developed in view of ultra-sensitive high dynamic range passive starring arrays, active 2D/3D and dual-mode passive-active imaging, which is why both the passive imaging performance and the gain characteristics of the APDs are of interest. A passive mode responsivity operability of 99.9% was measured in LPE and MBE e-APDs FPAs associated with an average NETD=12mK, demonstrating that dual mode passive-active imaging can be achieved with LETI e-APDs without degradation in the passive imaging performance. The gain and sensitivity performances were measured in test arrays and using a low voltage technology (3.3V) CTIA test pixel designed for 3D active imaging. The CTIA and test arrays measurements yielded comparable results in terms of bias gain dependence (M=100 at V(b)=-7V), low excess noise factor (< F >=1.2) and low equivalent input current (I(eq_in)<1pA). These results validated the low voltage CTIA approach for integrating the current from a HgCdTe e-APD under high bias. The test array measurements demonstrated a relative dispersion below 2% in both MBE and LPE e-APDs for gains higher than M>100, associated with an operability of 99%. The operability at I(eq_in)<1pA at M=30 was 95%. A record low value of I(eq_in)=1fA was estimated in the MBE e-APDs at M=100, indicating the potential for using the MW e-APDs for very low flux applications. The high potential of the MW e-APDS for active imaging was demonstrated by impulse response measurements which yielded a typical rise time lower than 100ps and diffusion limited fall time of 900ps to 5ns, depending on the pixel pitch. This potential was confirmed by the demonstration of a 2ns time of flight (TOF) resolution in the CTIA e-APD 3D pixel. The combined photon and dark current induced equivalent back ground noise at f/8 with a cold band pass filter at lambda=1.55 mu m was 2 electrons rms for an integration time of 50ns.

Tactical applications are very sensitive to maintenance periodicity and in lot of cases, maintenance position is critical regarding mission availability. Moreover, maintenance has a cost that becomes quickly prohibitive when the cooler or the vacuum have to be repaired too often. Sofradir has worked a lot during last years on reliability and life cycle cost optimization considering all the IR detectors subassemblies. This work has lead to an increased robustness of detectors and technologies even under severe environmental conditions, and reduced variabilities in production. This paper presents the state of the art of Integrated Detector Dewar Cooler Assembly (IDDCA)'s reliability, the production means and the methods that allow us today to propose detectors with very high reliability without maintenance. These detectors are a breakthrough for life cycle cost for tactical applications as portable cameras, airborne systems, and missiles.

The Molecular Beam Epitaxy (MBE) approach was under investigation for several years to prepare both the very large array fabrication and the 3rd generation developments. This large step in Infrared (IR) detector mass production is also necessary for producing third generation of IR detectors such as bicolor and dual band FPAs which use more complex multi hetero-junctions architectures.These new advanced HgCdTe technologies necessary for third generation developments have been validated and their producibility have been improved.As far as dual band IR detectors are concerned, the technologies are developed and a full TV format (24 mu m pixel pitch) is currently under development with a first application in bicolor within medium waveband.Future improvements including avalanche photodiodes (APD), will lead to more compact systems as well as a low cost approach.

HgCdTe (Mercury Cadmium Telluride / MCT) staring arrays for infrared detection do show constant improvements regarding their compactness and performances. New detectors are now proposed offering system solutions in the different IR wavebands and taking advantage of the latest technology improvements as well as MCT performance advantages and cost reduction.Based on 20 years of experience in 50 mu m to 15 mu m pitch Infrared (IR) detector production, the challenge of mass production of low-cost small-pixel pitch detectors are reviewed, from the IR chip manufacturing including detection material, hybridization, ROIC, to the integration in final packing. Taking advantage of its simple well known existing process, then the analyzes of all technological steps adapted to small pitch IR detector are presented, in terms of product performance, reliability, process statistics and capability in order to achieve high yield and low product cost. Answers given the low-cost small-pitch IR detector mass productions finally give benefits to application in terms of high performance, cost reduction, extended life time, and on the field system Life Cycle SupportAmong these new detectors, one can find the family of 15 mu m pixel pitch detectors a TV format (640 x 512) integrated in dedicated tactical Dewars, taking advantages on last development in coolers manufacturing and Dewar assembly.

Sofradir started to work in the field of space applications and especially in the earth observation domain in the beginning of the 1990th. Thanks to the work done with the support of the French Ministry of Defense and the European Space Agency, Sofradir has acquired a large know-how and has become a major supplier for European space industry. Nowadays, Sofradir technologies offer possibilities to develop a large panel of high reliable detectors like long linear arrays or two dimensional arrays covering bandwidth from visible to 15 μm and more based on qualified Mercury Cadmium Telluride (MCT) technology. As a matter of fact, Sofradir is involved in several projects for future space missions (SPIRALE, Bepi Colombo, MTG, SGLI...). This paper proposes an overview of Sofradir technology capabilities and experience for design of custom space detectors. In particular this paper presents latest developments for space applications with new results in visible, long wavelength and space qualification of infrared detectors.

In this paper we present an overview of the very recent developments of the HgCdTe infrared detector technology developed by CEA-LETI and industrialized by Sofradir in France. Today Sofradir uses in production for more than 15years a very mature, reproducible, well mastered and fully understood, planar n on p ion implanted technology. This process that allows very high yields to be achieved in all infrared bands from SWIR to LWIR uses the very conventional approach of LPE growth of MCT on lattice-matched CdZnTe substrates. Progress in this field is continuous from 20years and has recently leaded to the fabrication of high performance VLWIR FPA (320x256 with cut off wavelengths as high as 20μm). Moreover, thanks to the design of the epitaxial structure and to the substrate removal step MCT FPAs present the unique features to have very high quantum efficiency (above 70%) from the cut off wavelength down to the UV. This effect, which opens new application fields, was recently demonstrated in SWIR 320x256 FPAs with cut off wavelength of 2.5μm. Very high quality FPAs (1280x1024) with pitches as small as 15μm have already been demonstrated last year using the MBE growth of MWIR MCT epilayers on 4 inches germanium substrates, n on p ion implanted photodiodes and the hot welding indium bump hybridization technique. At the same time, with the MBE growth, bicolor and dual band FPAs which uses more complex multi hetero-junctions architectures (both 4 layers npn and 'pseudo planar' structures and extrinsically doped MCT layers) were fabricated with formats of 320x256 and pitches as small as 25μm. A very new area of development concerns avalanche photodiodes (APD) made with MCT. This semiconductor presents a unique feature among all the over semiconductors. Extremely high avalanche gains can be obtained on n on p photodiodes without absolutely any noise excess (F(K)=1): MCT APDs act as perfect amplifiers. These results open new interesting fields of investigation for low flux applications and fast detectors (including hyper spectral imaging and active imaging).

Environmental conditions (thermal, vibrations and shocks) are key performance and reliability factors for designing IR detectors. To address these constraints Sofiradir has developed specific concepts to make the IR detector more robust in stringent environmental conditions. This paper describes these design concepts that involve both the IRFPA (IR Focal Plane Array) and the cryogenics part, as well as the level of robustness that is achieved.

The post correction uniformity performance of infrared 2D starring arrays is a key factor to ensure the best IR image quality at the camera level. SOFRADIR has conducted several studies to improve both the post correction uniformity performance and the correction tables stability over the time periods, the readout integrated circuit configuration and the environmental conditions. Indeed, works have been performed on the homogeneity technology deposits, on the improvement of the readout circuit linearity and on the optimization of the dewar design to reduce the parasitical fluxes. Thanks to these improvements, Sofradir offers to its customers high level post correction uniformity performances as well as excellent correction tables stability for the mid wave and long wave infrared band. Thus, the calibrations constraints are reduced at the camera level and the image quality is optimized over a large camera utilization conditions.

The staring array numbers of pixels are larger and larger and offer system solutions in the different IR wavebands. At Sofradir, the HgCdTe (Mercury Cadmium Telluride IMCT)material and process, as well as the hybridization technology, have been taken to an even more advanced level of sophistication to achieve these new high performance staring arrays. A lot of technological improvement have been made regarding uniformity of Focal Plan Arrays (FPA), read-out circuits with new functions like the Analog to Digital Conversion (ADC), and finally the reliability of the whole dewar detector and cooler assembly have been drastically increased during these last years. In mid-wave (MWIR) l280x1024 HgCdTe high performance staring array is presented. Also, development trends for future IR detectors are presented.

Cooled IR detectors are produced at mass production level at Sofradir for years based on its mature and proven HgCdTe technology. However, following the market needs, a lot of progress have been made and allow Sofradir to offer new product designs mainly dealing with the simplification of the detector use as well as reliability improvements. In addition to the conventional technologies used at mass production level, the Molecular Beam Epitaxy (MBE) approach has been under investigation for several years to prepare both the very large array fabrication and the new (3rd) generation developments. CEA-Leti, in cooperation with Sofradir, obtained very good results on 4-inches wafer size which confirms the mastering of this growth process. Very high qualities FPAs (1280×1024), with pitches as small as 15μm, were demonstrated as well as bicolor and dual band FPAs which use more complex multi hetero-junctions architectures. A very new development at CEA-Leti concerns avalanche photodiodes (APD) made with HgCdTe which presents a unique feature among all the over semiconductors: extremely high avalanche gains can be obtained on n on p photodiodes without absolutely any noise excess. These results open new interesting fields of investigation for low flux applications and fast detectors. The cooled IR detector field is progressing very rapidly and new developments will offer a lot of system simplification and enhancements.

The Japanese Aerospace Exploration Agency (JAXA) will be conducting the Global Change Observation Mission (GCOM) for monitoring of global environmental change. SGLI (Second Generation Global Imager) is an optical sensor on board GCOM-C (Climate), that includes a Long Wave IR Detector (LWIRD) sensitive up to about 13 μm. SGLI will provide high accuracy measurements of the atmosphere (aerosol, cloud ...), the cryosphere (glaciers, snow, sea ice ...), the biomass and the Earth temperature (sea and land). Sofradir is a major supplier of Space industry based on the use of a Space qualified MCT technology for detectors from 0.8 to 15 μm. This mature and reproducible technology has been used for 15 years to produce thousands of LWIR detectors with cut-off wavelengths between 9 and 12 μm. NEC Toshiba Space, prime contractor for the Second Generation Global Imager (SGLI), has selected SOFRADIR for its heritage in space projects and Mercury Cadmium Telluride (MCT) detectors to develop the LWIR detector. This detector includes two detection circuits for detection at 10.8 μm and 12.0 μm, hybridized on a single CMOS readout circuit. Each detection circuit is made of 20x2 square pixels of 140 μm. In order to optimize the overall performance, each pixel is made of 5x5 square sub-pixels of 28 μm and the readout circuit enables sub-pixel deselection. The MCT material and the photovoltaic technology are adapted to maximize response for the requested bandwidths: cut-off wavelengths of the 2 detection circuits are 12.6 and 13.4 μm at 55K. This detector is packaged into a sealed housing for full integration into a Dewar at 55K. This paper describes the main technical requirements, the design features of this detector, including trade-offs regarding performance optimization, and presents preliminary electro-optical results.