Semi-Conductor Devices’ long-wave infrared 640 × 512/15-μm pitch type II superlattice detector is based on an XBp design with an InAs/GaSb absorbing layer and an InAs/AlSb barrier layer. The barrier architecture ensures a low, diffusion-limited, dark current and allows stable passivation to all fabrication steps. It is shown that the dark current is about 10 times the Rule 07 value and corresponds to a minority carrier lifetime of about 10 ns, while the quantum efficiency can approach within 10% of the HgCdTe value for realistic detector parameters. Detectors are now being manufactured with a reasonable yield for an operability above 99.5%, and a stable and reproducible noise equivalent temperature difference of < 15 mK when operated at 30 Hz, F/2.7 and 77 K.
For the highest end mid-wave-infrared applications, SCD, France offers a family of cryogenically cooled detectors with background limited performance (BLIP). The matured InSb Planar technology is implemented in a variety of focal plane arrays, from a 320 x 256 format with a 30 mu m pitch to a 1280 x 1024 format with a 15 mu m pitch, all of which are operated at 77K. A major challenge is to reduce the cooling requirements. Then substantial reductions in size, weight, and power (SWaP) can be achieved by using a smaller cooler and Dewar assembly. SCD's new epi-InSb detectors, grown by molecular beam epitaxy, have a BLIP temperature of 100 K at F/3. This enhanced operating temperature reduces the required cooling power by similar to 20 % compared with the conventional 77 K operation. For a very high operating temperature, we have developed the new XBn-InAsSb detector with a 4.2 mu m cut-off wavelength. This detector exhibits a BLIP temperature of similar to 160K at F/3 and a reduction in cooling power of similar to 60 %. These HOT detectors enable an improved range of solutions, including faster cool-down time and mission readiness, longer mission times, and higher cooler reliability. We can also exploit their reduced dark current to obtain an enhanced signal to noise ratio at lower operating temperatures.The well-established 25 mu m pitch family of uncooled mu-Bolometer detectors has two basic formats, 384 x 288 and 640 x 480, and several sensitivity grades. The very high sensitivity 25 mu m pitch detector has been demonstrated at F/2.4 for mid-range systems. The wide-band detector is optimized for both the long-wave-infrared and mid-wave-infrared spectral bands. Recently we developed the new 17 mu m pitch family of detectors. The 640 x 480 format is a leading candidate for applications such as thermal weapon sights, driver vision enhancers and other mid-range IR systems. The 17 mu m family is currently being expanded with the high sensitivity grade and with the addition of two new formats: the compact 384 x 288 for low SWaP applications, and the large 1024 x 768 format for applications requiring high resolution and a wide field of view.
A bariode is a new type of "diode-like" semiconductor photonic device, in which the transport of majority carriers is blocked by a barrier in the depletion layer, while minority carriers, created thermally or by the absorption of light, are allowed to pass freely across the device. In an n-type bariode, also known as an XB(n)n structure, both the active photon absorbing layer and the barrier layer are doped with electron donors, while in a p-type bariode, or XB(p)p structure, they are both doped with electron acceptors. An important advantage of bariode devices is that their dark current is essentially diffusion limited, so that high detector operating temperatures can be achieved. In this paper we report on MWIR n-type bariode detectors with an InAsSb active layer and an AlSbAs barrier layer, grown on either GaSb or GaAs substrates. For both substrate types, the bariodes exhibit a bandgap wavelength of similar to 4.1 mu m and operate with Background Limited Performance (BLIP) up to at least 160K at F/3. Different members of the XB(n)n device family are investigated, in which the contact layer material, "X", is changed between n-InAsSb and p-GaSb. In all cases, the electro-optical properties of the devices are similar, showing clearly the generic nature of the bariode device architecture. Focal Plane Array detectors have been made with a pitch of 15 or 30 mu m. We present radiometric performance data and images from our Blue Fairy (320x256) and Pelican (640x512) detectors, operating at temperatures up to 180K. We demonstrate for both GaSb and GaAs substrates that detector performance can be achieved which is close to "Rule 07", the benchmark for high quality, diffusion limited, Mercury Cadmium Telluride (MCT) devices.
Recently, a new "XBn" device architecture, based on heterostructures, has been proposed as an alternative to a homojunction photodiode. The main difference is that no depletion layer exists in any narrow bandgap region of the device. Instead, the depletion layer is confined to a wide bandgap barrier material. The Generation-Recombination (G-R) contribution to the dark current is then almost totally suppressed and the dark current becomes diffusion limited. This lowering of the dark current allows the device operating temperature to be raised relative to that of a standard photodiode made from the same photon absorbing material, with essentially no loss of performance. At SCD we have been developing XBn devices grown on GaSb substrates with an InAsSb photon absorbing layer and an AlSbAs barrier layer. The results of optical and electrical measurements are presented on devices with a bandgap wavelength of about 4.1μm. Strong suppression of the G-R current is demonstrated over a range of almost two orders of magnitude in the doping of the photon absorbing active layer (AL), while at the same time very high internal quantum efficiencies are achieved. A model of the spectral response is developed which can reproduce the observed behaviour very well at 88K and 150K over the whole AL doping range. In properly optimized devices, the BLIP temperature is shown to be in the region of 160K at f/3.
In this paper SCD's 17μm pitch large format VOx μ-Bolometer detector is introduced. In the first part the radiometric performance and the challenges involved in achieving the desired pixel sensitivity are discussed. We elaborate on the progress towards the performance design goal (< 50mK@F/1, 60Hz) utilizing various test structures and technology demonstration platforms. The combination of reduced pixel size and high-end thermal sensitivity can provide smaller light weight systems. In the second part the ROIC architecture options will be presented in depth. New capabilities and features are enabled by the advanced 0.18um VLSI technology. Explicitly, we address the contribution in terms of system flexibility, simplification and reduced power dissipation. Some vital tasks, such as coarse non-uniformity correction, are done internally thus facilitating the user interface.
