HgCdTe-based FPAs that can be used in high neutron radiation environments were designed and fabricated by EPIR, and tests using Fermi National Accelerator Laboratory’s neutron beam confirmed that these FPAs can maintain imaging functionality while exposed to fluxes up to low-1E13 neutron per squared centimeter accumulated neutron exposure. Monte Carlo N-Particle (MCNP) simulations were used to find that the energy deposited into the HgCdTe FPA can come from not only directly impinging neutrons but also scattered neutrons and subsequently generated protons, electrons and photons, confirming that our neutron-hardened designs are also hardened against other high energy particles. To mitigate radiation damage, we redesigned the optical system of the camera using modeling and simulation by utilizing MCNP code during our camera design. By properly choosing mirror substrate material and coating as well as the corresponding optical system and the camera design, we can filter out harmful radiation flux while still collecting the MWIR signal with high efficiency, thereby significantly reducing camera and image system performance degeneration under high-energy high-flux neutron beams.
Several MWIR nBn HgCdTe devices grown on silicon were studied. While several parameters are varied in the study, the devices can most usefully be put into 2 groups: those with a type 3 HgTe/CdTe superlattice barrier and those simply with a wider bandgap alloy barrier. Other groups have shown the potential advantage of a super-lattice barrier. Many devices were grown and fabricated, and were run through several optical and electrical tests to evaluate their properties. Utilizing the finite volume method based semiconductor device modeling software Devsim, these devices were simulated to extract further material parameters.
Pixel pitch size reduction was not the focus in early infrared (IR) detector development for a long time with pixel pitch remained at 24 μm or above. Pitch size reduction today is the key enabler for cost-efficient manufacturing of large format arrays and allows compact IR-systems with high spatial resolution. When mastered the smaller pixel pitch geometries will provide consistent range performance in a smaller package, minimized aliasing and false alarm rates, ability to use faster F/# optics and shorter focal length for long range identification and optimized size, weight and power (SWaP) characteristics. Advanced integration technologies (including three-dimensional integration) are necessary to realize small pitch arrays.
EPIR, Inc. has developed thermomechanical stress aware approach for advanced integration of IR focal plane arrays (IRFPAs) – MoDiBI. As intended, MoDiBI allows for favorably addressing the reliability concerns associated with the conventional integration approaches. The current work focuses on extending MoDiBI to small pixel pitch, large format IRFPA integration. Strategies for optimizing the thermal stress induced in the hybridized assembly during thermal cycling, thereby helping in reducing the fatal failures experienced by IRFPAs will be discussed. Applicability of MoDiBI to 1280×720, 8µm pitch IRFPAs will be presented.
Novel integration method that addresses thermo-mechanical reliability of the IRFPA hybrid assembly in advanced three-dimensional integration scheme requires optimization by engineering materials used for vertical integration and geometry engineering of the assemblies to be integrated. We present such optimization scheme and applicability of this method to vertical integration of HgCdTe and Type-II Superlattice (T2SL) based IRFPA.
Conference Committee Involvement (2)
Infrared Sensors, Devices, and Applications XIV
20 August 2024 | San Diego, California, United States
Infrared Sensors, Devices, and Applications XIII
22 August 2023 | San Diego, California, United States
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