Infrared MBE-Grown HgCdTe Focal Plane Arrays and Cameras After High Energy Neutron Irradiation
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https://doi.org/10.1007/s11664-020-08276-7 Ó 2020 The Minerals, Metals & Materials Society
TOPICAL COLLECTION: U.S. WORKSHOP ON PHYSICS AND CHEMISTRY OF II-VI MATERIALS 2019
Infrared MBE-Grown HgCdTe Focal Plane Arrays and Cameras After High Energy Neutron Irradiation YONG CHANG ,1,3 SILVIU VELICU,1 SUSHANT SONDE,1 and THOMAS KROC2 1.—EPIR Inc, 590 Territorial Drive Ste. H, Bolingbrook, IL 60440, USA. 2.—Fermi National Accelerator Laboratory, Batavia, IL 60510, USA. 3.—e-mail: [email protected]
HgCdTe is one of the most important materials for the fabrication of infrared detectors and focal plane arrays (FPAs) deployed in environments where highenergy particles, such as protons and neutrons, are present. We designed and fabricated HgCdTe-based FPAs that can be used in high neutron radiation environments and we measured their characteristics. The influence of the radiation on the infrared FPAs and cameras is investigated. HgCdTe material and devices are capable of maintaining high performances in a high energy neutron irradiation environment. For MWIR FPA directly facing a 2.59 9 108 n/cm2 s neutron flux beam (with the highest energy 66 MeV) for 1 h, the noise equivalent differential temperature (NEDT) increased 8 times after irradiation. However, NEDT decreased to 33 mK (compared to the original value of 21 mK) after one warming-up (to room temperature) and cooling-down cycle. The NEDT for the MWIR FPAs mounted parallel to the beam did not degrade (16 mK and 28 mK before irradiation, changed to 18 mK and 26 mK after irradiation, respectively). Key words: HgCdTe, infrared, focal plane array, FPA, infrared camera, IR, radiation hardening, neutron, thermal imaging
INTRODUCTION HgCdTe historically is one of the most widely used materials for the fabrication of high-performance infrared (IR) detectors and focal plane arrays (FPAs). HgCdTe’s bandgap can be conveniently adjusted by varying the Hg-to-Cd ratio. HgCdTe has large optical absorption coefficients, long carrier recombination lifetimes, and diffusion lengths which enable high quantum efficiency and functioning at high operating temperatures. Furthermore, HgCdTe-based IR FPAs have been developed for use in the extended short-wavelength infrared (eSWIR, 1-3 lm wavelength), mid-wavelength infrared (MWIR, 3-5 lm wavelength), and long-wavelength infrared (LWIR, 8-14 lm wavelength) regions in
(Received March 4, 2020; accepted June 14, 2020)
military and civilian applications.1 In addition, HgCdTe can also be used for visible and even ultraviolet imaging if the visible light absorbing substrates (CdZnTe, Si, or GaAs) are removed. HgCdTe-based IR FPAs are commonly utilized for the fabrication of IR cameras. HgCdTe is a proven technology for high radiation environments.1–4 HgCdTe was found to have a high degradation threshold that is approximately two orders of magnitude higher than in III-V materials and three orders higher than in Si. Pickel and colleagues2 reported the 78 K displacement damage threshold of fission neutrons, 2-MeV neutrons, and 14-MeV neutrons
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