Defects study in IR photodetectors by DLTS

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Defects Study in Hg x Cd1−x Te Infrared Photodetectors by Deep Level Transient Spectroscopy

International audienceAt high temperature, infra-red focal plane arrays are limited by their performance in operability, detectivity D (*) or noise equivalent temperature difference. Trap characterization and defect studies are necessary to better understand these limitations at high temperature. In this paper, we use deep level transient spectroscopy to study electrically active defects in mercury cadmium telluride n (+)/p diodes. The material investigated has a cut-off frequency (lambda (c)) of 2.5 mu m at 180 K and p doping performed with mercury vacancy. Trap energy signatures as well as capture cross-section measurements are detailed. A low temperature hole trap close to midgap is observed in the range 150-200 K with an activation energy around 0.18 +/- A 0.025 eV. A high temperature hole trap is also observed in the range 240-300 K with an activation energy of 0.68 +/- A 0.06 eV. A hole capture cross-section of 10(-19) cm(2) is obtained for both traps. The nature of the defects and their correlation with dark current are discussed

Low dark current p-on-n technology for space applications

International audienceSpace applications are requiring low dark current in the long wave infrared at low operating temperature for low flux observation. The applications envisioned with this type of specification are namely scientific and planetary missions. Within the framework of the joint laboratory between Sofradir and the CEA-LETI, a specific development of a TV format focal plane array with a cut-off wavelength of 12.5 mu m at 40K has been carried out. For this application, the p on n technology has been used. It is based on an In doped HgCdTe absorbing material grown by Liquid Phase Epitaxy (LPE) and an As implanted junction area. This architecture allows decreasing both dark current and series resistance compared to the legacy n on p technology based on Hg vacancies. In this paper, the technological improvements are briefly described. These technological tunings led to a 35% decrease of dark current in the diffusion regime. CEA-LETI and Sofradir demonstrated the ability to use the p on n technology with a long cutoff wavelength in the infrared range

Anisotropic transport investigation through different etching depths in InAs/InAsSb T2SL barrier midwave infrared detector

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Enhanced two-photon-absorption using sub-wavelength antennas

International audienceDegenerate two-photon absorption (TPA) is investigated in a 186 nm thick gallium arsenide (GaAs) p-in diode embedded in a resonant metallic nanostructure. The full device consists in the GaAs layer, a gold subwavelength grating on the illuminated side, and a gold mirror on the opposite side. For TM-polarized light, the structure exhibits a resonance close to 1.47 μm, with a confined electric field in the intrinsic region, far from the metallic interfaces. A 109 times increase in photocurrent compared to a non-resonant device is obtained experimentally, while numerical simulations suggest that both gain in TPA-photocurrent and angular dependence can be further improved. For optimized grating parameters, a maximum gain of 241 is demonstrated numerically and over incidence angle range of (−30°; +30°). This structure paves the way towards low-noise infrared detection, using non-degenerate TPA, involving two photons of vastly different energies in the same process of absorption in a large bandgap semiconductor material