Broadband enhancement of mid-wave infrared absorption in a multi resonant nanocrystal-based device
Résumé
Light management is one of the main challenges to address when designing a sensor from a nanocrystal (NC) array. Indeed, the carrier diffusion length, limited by hopping mechanism, is much shorter than the absorption depth. Several types of resonators (plasmon, Bragg mirror, guided mode, Fabry-Perot cavity) have been proposed to reduce the volume where light is absorbed. All of them are inherently narrow bands, while imaging applications focus on broadband sensing. Here, we propose an infrared sensor in the short and mid-wave infrared (SWIR and MWIR) that combines three different photonic modes to achieve broadband enhancement of the light absorption. Moreover, we show that these three modes can be obtained from a simple structure where the NC film is coupled only to a grating and a top metallic layer. The obtained device achieves a high responsivity of >700 mA.W-1 , a detectivity up to 2x10 10 Jones at 80 K, and a short response time of 11 µs.
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