Nanocrystal-Based Active Photonics Device through Spatial Design of Light-Matter Coupling

Abstract

The integration of photonic structures in nanocrystal (NC)-based photodetectors has been demonstrated to improve device performances. Furthermore, bias-dependent photoresponse can be observed in such devices as a result of the interplay between hopping transport and inhomogeneous electromagnetic field. Here, we investigate the main physical concepts leading to a voltage-dependent photoresponse. We first bring evidence of bias-dependent carrier mobilities in a NC array over a wide range of temperatures. Then, we fabricate an infrared sensing device using HgTe NCs, where the electrodes also play the role of a grating, inducing a spatially inhomogeneous absorption. The obtained device exhibits a significant bias-dependent photoresponse while possessing a competitive detection performance in the extended short-wave and mid-wave infrared, with detectivity reaching 7 × 1010 Jones at 80 K and a fast response time of around 70 ns. This work provides the foundation for further advancements in NC-based-active photonics devices.

Bias Reconfigurable Photoresponse of an Infrared Nanocrystal Film Integrated into a Coupled Fabry-Perot Resonator

“…To design an NC-based active device, whose spectral response can be tuned through bias application, the role of the photonic structure is to induce an inhomogeneous absorption map. In previous devices, , two electromagnetic modes have been used: one, close to the electrode, will prevail under low electric field and the second, away from the electrode, will contribute to photocurrent only when the applied bias increases the diffusion length. Here, we adopt a different approach and directly design a bicolor structure where the two modes are spatially disjoint.…”

“…Various photonic concepts have been proposed to enhance the absorption efficiency and shape the absorption spectrum: flat lenses, Fabry-Perot resonators, magnification of the field by metal tips, plasmonic cavities, ,, Bragg mirrors, guided-mode resonators, , metal–insulator–metal cavities, metasurfaces, epsilon-near-zero resonances, , Helmholtz resonators, and combinations of these. , The first purpose of these photonic structures is to modify either the magnitude or the linewidth of the absorption. However, it has also been proposed that photonic structures can actively modify the shape of the spectrum , after the device fabrication. For this, two requirements should be met: (i) the photonic structure needs to generate an inhomogeneous absorption map within the device, (ii) the charge collection needs to be electric-field-dependent.…”

“…Since the spatial distribution of the absorption field map varies with the wavelength, this effect can be used to generate a bias-reconfigurable photoresponse. However, the magnitude of the effect reported , so far remains too weak to be used, asking for the development of alternative structures. Here, we explore the coupled Fabry-Perot − (cFP) resonator.…”

Mercury chalcogenide colloidal quantum dots for infrared photodetection: from synthesis to device applications

“…120 With bottom illumination, a transverse magnetic (TM)-excited cavity mode between the top and bottom metal stripes, and a TMexcited surface plasmon mode at the QD/metallic layer interface and a transverse electric (TE)-excited resonance over the slit region were all obtained, resulting in a broadband enhancement of light absorption from 2 to 4 µm compared to bare QD films and a high responsivity of >0.7 A W −1 measured under 980 °C blackbody radiation. Similar photonic structures illustrated the potential of the QD film as a light modulator with a bias-tuneable spectral response, 122,123 which originated in the inhomogeneous absorption in the QD film and the biasdependent charge diffusion length.…”

Lithium-Ion Glass Gating of HgTe Nanocrystal Film with Designed Light-Matter Coupling

“…Fabrication of gold nano-stripes: The procedure was similar to the one used in ref [ 45 ]. We used a Raith eLine e-beam lithography system for the fabrication of the nano-stripes.…”