Nicolas Péré-Laperne

Infrared SWAP detectors: pushing the limits

The growing demand for compact and low consumption infrared cooled detectors is driven by different products segments. Hand Held Thermal Imagers, UAV, small gimbals are some of them. End users are requiring devices easy to use with fast cool down time, excellent portability, low acoustic noise with no trade-offs in reliability and performance. These requirements are pushing the technology developments toward constant innovations on detectors, coolers, read out circuits and proximity electronic boards. In this paper we are discussing the different figures of merit and highlighting the challenges for the different components. An update on the developments of HOT technology for most advanced pixel pitch will be presented. Very compact products are driving the developments for innovative coolers and cryogenic solutions. A low power compact architecture is a must for electronic boards to optimize the overall system power consumption. Finally a look to the future requirements for further shrink will be addressed.

Update on 10μm pixel pitch MCT-based focal plane array with enhanced functionalities

Sofradir was first to show a 10μm focal plane array (FPA) in DSS 2012, and announced the DAPHNIS 10μm product family back in 2014. This pixel pitch is key for enabling more compact sensors and increased resolution. SOFRADIR recently achieved outstanding MTF demonstration at this pixel pitch, which clearly demonstrate the benefit to users of adopting 10μm pixel pitch focal plane array based detectors. The last results, and associated gain in detection performance, are discussed in this paper. Concurrently to pitch downsizing, SOFRADIR also works on a global offer using digital interfaces and smart pixel functionalities. This opens the road to enhanced functionalities such as improved image quality, higher frame rate, lower power consumption and optimum operation for wide thermal conditions scenes. This paper also discusses these enhanced features and strategies allowing easier integration of the detector in the system.

HgCdTe APDS for space applications

HgCdTe avalanche photodiode focal plane arrays (FPAs) and single element detectors have been developed for a large scope of photon starved applications. The present communication present the characteristics of our most recent detector developments that opens the horizon for low infrared (IR) photon number detection with high information conservation for imaging, atmospheric lidar and free space telecommunications. In particular, we report on the performance of TEC cooled large area detectors with sensitive diameters ranging from 30- 200 μm, characterised by detector gains of 2- 20 V/μW and noise equivalent input power of 0.1-1 nW for bandwidths ranging from 20 to 400 MHz.

Getting small: new 10μm pixel pitch cooled infrared products

Recent advances in miniaturization of IR imaging technology have led to a burgeoning market for mini thermalimaging sensors. Seen in this context our development on smaller pixel pitch has opened the door to very compact products. When this competitive advantage is mixed with smaller coolers, thanks to HOT technology, we achieve valuable reductions in size, weight and power of the overall package. In the same time, we are moving towards a global offer based on digital interfaces that provides our customers lower power consumption and simplification on the IR system design process while freeing up more space. Additionally, we are also investigating new wafer level camera solution taking advantage of the progress in micro-optics. This paper discusses recent developments on hot and small pixel pitch technologies as well as efforts made on compact packaging solution developed by SOFRADIR in collaboration with CEA-LETI and ONERA.

Hgcdte avalanche photodiodes: Application for infra-red detection

HgCdTe avalanche photodiode focal plane arrays (FPAs) and single element detectors have been developed for a large scope of photon starved applications. The present communication present the characteristics of our most recent detector developments that opens the horizon of low infrared (IR) photon number detection with high information conservation for imaging, atmospheric lidar and free space telecommunications. In particular, we report on the performance of TEC cooled large detectors with sensitive diameters ranging from 30-200 μm characterised by detector gains of 2-20 V/μW W and noise equivalent input power of 0.1-1 nWfor bandwidth ranging from 20-400 MHz.

Latest improvements on long wave p on n HgCdTe technology at Sofradir

SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. As a result, strong and continuous development efforts are deployed to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, dark current, quantum efficiency, low excess noise and high operability. The actual trend in quantum IR detector development is the design of very small pixel, with the higher achievable operating temperature whatever the spectral band. Moreover maintaining the detector operability and image quality at higher temperature moreover for long wavelength is a major issue. This paper presents the recent developments achieved at Sofradir to meet this challenge for LW band MCT extrinsic p on n technology with a cut-off wavelength of 9.3μm at 90K. State of the art performances will be presented in terms of dark current, operability and NETD temperature dependency, quantum efficiency, MTF, and RFPN (Residual Fixed Pattern Noise) stability up to 100K.

Recent advances on long wave p on n HgCdTe infrared technology

SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. As a result, strong and continuous development efforts are deployed to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, dark current, quantum efficiency, low excess noise and high operability. The actual trend in quantum IR detector development is the design of very small pixel, with the higher achievable operating temperature whatever the spectral band. Moreover maintaining the detector operability and image quality at higher temperature moreover for long wavelength is a major issue. This paper presents the recent developments achieved at Sofradir to meet this challenge for LW band MCT extrinsic p on n technology with a cut-off wavelength of 9.3μm at 90K. State of the art performances will be presented in terms of dark current, operability and NETD temperature dependency, quantum efficiency, MTF, and RFPN (Residual Fixed Pattern Noise) stability up to 100K.

Diffusion Mechanism for Arsenic in Intrinsic and Extrinsic Conditions in HgCdTe

Due to its low diffusivity and high activation rate, arsenic has become the dopant of choice in p/n HgCdTe high operating temperature technology. Its diffusion mechanism, however, remains imprecise. In this work, arsenic diffusion was studied in molecular beam epitaxy HgCdTe structures consisting of alternatively As-doped and intrinsic layers grown on a CdZnTe substrate. The diffusion coefficient of As was extracted from secondary ion mass spectroscopy concentration profiles. Annealings were performed for different temperatures, mercury partial pressures (PHg), annealing times and cadmium atomic fractions. Fermi-level effect on diffusion was observed, indicating extrinsic conditions for diffusion at high As concentration. Based on the variation of As diffusivity with PHg and As concentration, we propose that As diffusion occurs on both II and VI sublattices. Our results are consistent with the fact that AsVI diffusion is assisted by the Te interstitial, introducing donor levels in the bandgap, while AsII diffusion is assisted by the cation vacancy.

Low dark current p-on-n technology for space applications

Space applications are requiring low dark current in the long wave infrared at low operating temperature for low flux observation. The applications envisioned with this type of specification are namely scientific and planetary missions. Within the framework of the joint laboratory between Sofradir and the CEA-LETI, a specific development of a TV format focal plane array with a cut-off wavelength of 12.5μm at 40K has been carried out. For this application, the p on n technology has been used. It is based on an In doped HgCdTe absorbing material grown by Liquid Phase Epitaxy (LPE) and an As implanted junction area. This architecture allows decreasing both dark current and series resistance compared to the legacy n on p technology based on Hg vacancies. In this paper, the technological improvements are briefly described. These technological tunings led to a 35% decrease of dark current in the diffusion regime. CEA-LETI and Sofradir demonstrated the ability to use the p on n technology with a long cutoff wavelength in the infrared range.

Latest developments of 10μm pitch HgCdTe diode array from the legacy to the extrinsic technology

Sofradir recently presented Daphnis, its latest 10 μm pitch product family. Both Daphnis XGA and HD720 are 10μm pitch mid-wave infrared focal plane array. Development of small pixel pitch is opening the way to very compact products with a high spatial resolution. This new product is taking part in the HOT technology competition allowing reductions in size, weight and power of the overall package. This paper presents the recent developments achieved at Sofradir to make the 10μm pitch HgCdTe focal plane array based on the legacy technology. Electrical and electro-optical characterizations are presented to define the appropriate design of 10μm pitch diode array. The technological tradeoffs are explained to lower the dark current, to keep high quantum efficiency with a high operability above 110K, F/4. Also, Sofradir recently achieved outstanding Modulation Transfer Function (MTF) demonstration at this pixel pitch, which clearly demonstrates the benefit to users of adopting 10μm pixel pitch focal plane array based detectors. Furthermore, the HgCdTe technology has demonstrated an increase of the operating temperature, plus 40K, moving from the legacy to the P-on-n one at a 15μm pitch in mid-wave band. The first realizations using the extrinsic P-on-n technology and the characterizations of diodes with a 10μm pitch neighborhood will be presented in both mid-wave and long-wave bands.