Modeling the optical constants of HgxCd1−xTe alloys in the 1.5–6.0 eV range

Djurišić, Aleksandra B.; Li, E. Herbert

doi:10.1063/1.369605

Cited by 5 publications

(2 citation statements)

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“…The X-rays produced by the 55 Fe source are predominantly Mn KL 2 +KL 3 X-rays with energy 5.89 keV (Deslattes et al 2003(Deslattes et al , 2005, which in Hg 1−x Cd x Te with x = 0.445 have an opacity of 523 cm 2 g −1 (Berger et al 2010); at the absorber density of ρ = 7.07 g cm −3 (Capper 1994), this corresponds to an absorption depth of (κρ) −1 = 2.7 μm, or about half of the thickness of the Hg 1−x Cd x Te absorber. In contrast, the absorption depth of a photon at 500 nm in Hg 1−x Cd x Te is 28 nm (Djurišić & Li 1999; in practice, such a photon may be absorbed in the buffer layer). We thus anticipate that holes released by X-ray absorption events likely travel only part way through the absorbing layer, and thus on average may give a lower charge diffusion length than a measurement with visible light.…”

Section: Discussionmentioning

confidence: 99%

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Quantum Yield and Charge Diffusion in the Nancy Grace Roman Space Telescope Infrared Detectors

Givans

Choi

Porredon

et al. 2022

PASP

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Weak gravitational lensing is a powerful tool for studying the growth of structure across cosmic time. The shear signal required for weak lensing analyses is very small, so any undesirable detector-level effects which distort astronomical images can significantly contaminate the inferred shear. The Nancy Grace Roman Space Telescope (Roman) will fly a focal plane with 18 Teledyne H4RG-10 near-infrared (IR) detector arrays; these have never before been used for weak lensing and they present different instrument calibration challenges relative to charge-coupled devices. A pair of previous investigations demonstrated that spatiotemporal correlations of flat field images can effectively separate the brighter-fatter effect (BFE) and interpixel capacitance (IPC). A third paper in the series introduced a Fourier-space treatment of these correlations which allowed the authors to expand to higher orders in BFE, IPC, and classical nonlinearity. This work expands the previous formalism to include quantum yield and charge diffusion. We test the updated formalism on simulations and show that we can recover input visible characterization values to within a few percent. We then apply the formalism to visible and IR flat field data from three Roman flight candidate detectors. We find that BFE is present in all detectors and that the magnitude of its central pixel value is comparable between visible data and IR data. We fit a 2D Gaussian model to the charge diffusion at 0.5 μm wavelength, and find variances of C 11 = 0.1066 ± 0.0011 pix2 in the horizontal direction, C 22 = 0.1136 ± 0.0012 pix2 in the vertical direction, and a covariance of C 12 = 0.0001 ± 0.0007 pix2 (stat) for SCA 20829. Last, we convert the asymmetry of the charge diffusion into an equivalent shear signal using the sensitivity coefficients for the Roman survey, and find a contamination of the shear correlation function to be ξ + ∼ 10−6 for each detector. This exceeds Roman’s allotted error budget for the measurement by a factor of  ( 10 ) in power (amplitude squared) but can likely be mitigated through standard methods for fitting the point-spread function (PSF) since for weak lensing applications the charge diffusion can be treated as a contribution to the PSF. Further work considering the impact of charge diffusion and quantum yield on shear measurements will follow once all detectors covering the Roman focal plane are selected.

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Section: Discussionmentioning

confidence: 99%

“…For example, the E 1 critical point of 2.5 μm cutoff HgCdTe is at 1/λ = E 1 /hc = 2.0 μm −1 and dominates absorption of 500 nm light(Djurišić & Li 1999), whereas for 5 μm cutoff HgCdTe this critical point only shifts down to 1.9 μm −1(Viña et al 1984).…”

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confidence: 99%