Gate-controlled polarization-resolving mid-infrared detection at metal–graphene junctions

Abstract

The ability to resolve the polarization of light with on-chip devices represents an urgent problem in optoelectronics. The detectors with polarization resolution demonstrated so far mostly require multiple oriented detectors or movable external polarizers. Here, we experimentally demonstrate the feasibility to resolve the polarization of mid-infrared light with a single chemical-vapor-deposited graphene-channel device with dissimilar metal contacts. This possibility stems from an unusual dependence of photoresponse at graphene–metal junctions on gate voltage and polarization angle. Namely, there exist certain gate voltages providing the polarization-insensitive signal; operation at these voltages can be used for power calibration of the detector. At other gate voltages, the detector features very strong polarization sensitivity, with the ratio of signals for two orthogonal polarizations reaching [Formula: see text]. Operation at these voltages can provide information about polarization angles, after the power calibration. We show that such unusual gate- and polarization-dependence of photosignal can appear upon competition of isotropic and anisotropic photovoltage generation pathways and discuss the possible physical candidates.

Zero-Bias Photodetection in 2D Materials via Geometric Design of Contacts

“…We have shown that a versatile tool to achieve electromagnetically inequivalent contacts lies in exploiting polarization-dependent field enhancement by keen metal edges. 15,24 Such an effect may be even more pronounced for contacts with in-plane patterning, which may have either a regular (e.g., sawtooth) or fractal 33 shape. Interestingly, such detectors with one patterned contact can demonstrate nonzero photocurrent upon illumination with natural (nonpolarized) light, as we show with electromagnetic simulation in Supporting Information, Section IVb.…”

“…It has been already noted that a large fraction of photocurrent in 2DM-based detectors is formed at the Schottky junction between the 2D body and metal contacts. − This occurs both for visible light, where the built-in field separates electron–hole pairs, , and for long-wavelength radiation, where thermoelectric effects and current–voltage nonlinearities take place. , In a typical detector structure with 2DM placed between identical metals, the photocurrents of two Schottky junctions are exactly compensated, in agreement with symmetry requirements discussed above. Numerous works in the field dealt with contacts of dissimilar metals, ,,, which, however, requires extra technological steps and careful selection of work functions. If it was possible to “shadow” one of the Schottky junctions, the necessary asymmetry would be introduced, and one would get the desired zero-bias low-noise photodetector based on a 2D material.…”

“…12,13 In a typical detector structure with 2DM placed between identical metals, the photocurrents of two Schottky junctions are exactly compensated, in agreement with symmetry requirements discussed above. Numerous works in the field dealt with contacts of dissimilar metals, 9,12,14,15 which, however, requires extra technological steps and careful selection of work functions. If it was possible to "shadow" one of the Schottky junctions, the necessary asymmetry would be introduced, and one would get the desired zero-bias low-noise photodetector based on a 2D material.…”

“…Its operating principle is illustrated in Figure a, and its microphotograph is shown in the inset of Figure b, #1. The linearly polarized radiation with E -field orthogonal to one of the metal contacts is enhanced locally via a dynamic lightning-rod effect. , We call the respective junction as ‘electromagnetically active’. Near another contact, the incident field is suppressed due to reflection from the substrate and dynamic screening currents in the metal (see Supporting Information, Section IVc for details).…”