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7 May 2019 Ultra-thin super absorbing photon trapping materials for high-performance infrared detection
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The performance of mid- and long-wavelength infrared (IR) detectors is still restricted with the dark current characteristics and associated noise behavior. In this work, we propose reducing the dark current and related noise of the IR detectors to elevate high operating temperature and improve the detector quantum efficiency (QE), by using a thin absorption layer of IR absorbing materials like lead selenide (PbSe) and mercury cadmium telluride (HgCdTe). A photon bending and trapping mechanism based on integrated micro/nanoscale holes was employed to ensure high quantum efficiency despite using a thin absorbing layer. Using finite-difference time-domain (FDTD) method, the effect of embedded hole arrays on the optical absorption enhancement of ultra-thin PbSe and HgCdTe has been investigated. The calculated optical absorptions in ultra-thin IR structures without holes were compared with that of similar structures embedded with hole arrays. The optical absorption in 2 μm thick PbSe film without holes is less than 5% for 3-5 μm mid-IR wavelengths. Although applying conventional anti-reflecting (AR) coatings leads to a slightly higher absorption, it can cause higher dark current due to increased surface traps. Integration of hole arrays in 2 μm thick PbSe film has shown a significant optical absorption enhancement, up to 20% at 4.5 μm wavelength. This is equivalent to more than 2- and 4-folds' enhancement compared to a 2 μm thick flat-surface structure with AR and without AR, respectively. In addition, embedding the hole arrays in 1.2 μm thick HgCdTe IR films enhances the optical absorption up to 75% at 4.5 μm, which is more than 4 times higher than that in HgCdTe structure without holes. Additionally, the optical absorption in 1.2 μm thick HgCdTe film with periodic array of photon-trapping micro-holes enhances to 27% at 10 μm, long-IR wavelength. This is more that 3 times higher than that in HgCdTe films without holes. Our work revealed that the embedding hole arrays not only enhances the optical absorption in IR ultra-thin structures but also can reduce that material filling ratio to ~50%, which leads to a lower dark current, ensuring higher temperature operation of the IR detectors.
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Hossein Rabiee-Golgir, Soroush Ghandiparsi, Ekaterina Ponizovskaya Devine, Ahmed S. Mayet, Cesar Bartolo-Perez, Priyalal S. Wijewarnasuriya, Nibir K. Dhar, and M. Saif Islam "Ultra-thin super absorbing photon trapping materials for high-performance infrared detection", Proc. SPIE 11002, Infrared Technology and Applications XLV, 110020T (7 May 2019);

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