Polarization‐Sensitive and Broadband Photodetection Based on a Mixed‐Dimensionality TiS₃/Si p–n Junction

Abstract

polarization-sensitive photodetectors and polarimeters. [6] Up to now, however, most of the reported works on photodetectors based on 2D semiconductors are focused on transition metal dichalcogenides or other chalcogenides with marked in-plane isotropic properties and thus the built-up photodetectors are insensitive to polarized light. [3a,7] The amount of works exploring the use of dichroic 2D semiconductors is still scarce and they are mostly limited to devices with low detectivity values or with a limited cut-off wavelength. [8] Recently, Island et al. have fabricated photodetectors using TiS 3 , [7c] a member of the trichalcogenide family that presents remarkable quasi-1D electrical and optical properties with an anisotropy larger than the one of black phosphorus. [9] However, this strong in-plane anisotropy has not been exploited yet to fabricate polarization-sensitive photodetectors.Here, we demonstrate the fabrication of monolithic polarizationsensitive photodetectors based on TiS 3 . The devices are built up by staking a TiS 3 ribbon onto p-type silicon, thus forming a p-n junction based photodiode geometry which allows one to operate the device either in photovoltaic (PV) mode, without applying any external bias, or in photoconductive (PC) mode, with a positive or negative bias applied to the device. In PV mode upon illumination, the built-in electric field present at the interface between TiS 3 and Si separates the photogenerated charge carriers yielding to photocurrent even under unbiased condition. The fabricated devices show broadband photoresponse from 405 to 1050 nm and a strong dependence of their photoresponse on the polarization The capability to detect the polarization state of light is crucial in many daylife applications and scientific disciplines. Novel anisotropic 2D materials such as TiS 3 combine polarization sensitivity, given by the in-plane optical anisotropy, with excellent electrical properties. Here, the fabrication of a monolithic polarization-sensitive broadband photodetector based on a mixed-dimensionality TiS 3 /Si p-n junction is demonstrated. The fabricated devices show broadband responsivity up to 1050 nm, a strong sensitivity to linearly polarized illumination with difference between the two orthogonal polarization states up to 350%, and a good detectivity and fast response time. The discussed devices can be used as building blocks to fabricate more complex polarization-sensitive systems such as polarimeters.

Panchromatic All‐Polymer Photodetector with Tunable Polarization Sensitivity

“…While erroneous, this method allows for a comparison to other detectors reported in the literature that use this method. Under this view, the performance of the polarized detectors compare well to other all‐polymer organic photodetectors, and other intrinsic polarized detectors …”

“…While the polymers align in the direction of strain, the local polymer order in the film is kept allowing the films to maintain high quantum efficiency. In fact, the photodetector performance in terms of R , detectivity, and 3 dB cutoff frequency is among the highest reported for all‐polymer photodetectors, and intrinsically polarization‐sensitive organic or inorganic photodetectors . In summary, the demonstrated devices highlight the opportunity of all‐polymer photodetectors to achieve high‐performance intrinsically polarization‐sensitive photodetectors with broad spectral response.…”

“…If a broadband wire grid polarizer with a transmittance of 70% at 400 nm is placed in front of the device (e.g., WP12L‐UB, Thorlabs), the electrical output would be anticipated to be similar to the reported PBnDT‐FTAZ:P(NDI2OD‐T2) polarized detector that has a responsivity of 0.112 A W −1 . To remove the need for a polarizing optics in front of the detector, there have been recent reports that focus on exploiting the anisotropic properties of 2D materials for intrinsic sensitive photodetectors, such as TiS3, black phosphorous, and others . The performance of the all‐polymer photodetector reported here outperforms these demonstrations in terms of the combination of detectivity and response time.…”

“…The specific detectivity is typically the metric reported in the literature to describe the sensitivity of a photodetector . The detectivity is often determined by measuring or estimating the noise current and using the noise current along with responsivity.…”

Heterostructures formed through abraded van der Waals materials

“…70 . Photodetector devices with n-and p-type silicon substrates were produced by etching a 1 × 1 cm square of thermally grown SiO 2 with a sodium biflouride etch solution as described elsewhere 71 . The freshly exposed underlying Si was then directly abraded with TMDC powder until no pin-holes were observable under a ×50 microscope objective.…”