The sensitive detection of light polarization besides the intensity and wavelength, can provide a new degree of freedom for more and clearer information of imaging targets in night, fog, and smoke environment. However, the conventional filter-integrated polarimetric photodetectors suffer from the complicated fabrication process and limited spectral range. Herein, broadband and polarization-sensitive photodetectors are achieved with reconfigurable operation mode, utilizing the linear dichroism and narrow band gap of 2D As 0.4 P 0.6 with in-plane anisotropic structure. In As 0.4 P 0.6 -MoTe 2 heterojunction device, both photo-gating and photovoltaic modes are operated and switchable, contributing to high responsivity (1590 A W −1 at 405 nm and 14.7 A W −1 at 1550 nm) and ultrafast speed (25 µs) in the wide spectral band (405-1550 nm). Interestingly, an optical reversal is observed on both linear dichroism and polarimetric photocurrent due to the wavelengthdependent polarization reverse nature of the As 0.4 P 0.6 flakes. The dichroism ratio of photocurrent can be modulated from unity to ≈10 by varying the gate voltage, enabling the reconfigurable detection mode from polarizationindependence to polarization-susceptibility. This study demonstrates a new prototype device comprising low symmetric van der Waals heterostructure, possessing the gate-tunability on both photo-gain and dichroism ratio, toward high performance, reconfigurable, broadband, and polarizationresolved photodetection and imaging applications.
Atomically thin two-dimensional (2D) materials make it possible to create a variety of van der Waals (vdW) heterostructures with different physical features and attributes, which enables the growth of innovative electronics and optoelectronics applications. The band alignment and charge transfer play a crucial role in the physical and optoelectrical properties of the vdW heterostructure. Here, we design a vdW heterojunction device comprising low-symmetric CrOCl to induce a stable anti-ambipolar behavior and polarization-sensitive photodetection performance. 2D CrOCl exhibits strong in-plane anisotropy and linear dichroism, and an anti-ambipolar transport behavior is observed in a MoTe2 channel due to the gate-tunable band bending and charge transfer at MoTe2/CrOCl interface. The devices also exhibit well photodetection performance with a responsivity of 1.05 A/W and a temporal response of 970 μs. Owing to the anisotropic CrOCl serving as a photosensitizing layer, the device achieves the capability of polarization-sensitive photodetection with a photocurrent dichroic ratio up to ∼6. This work offers a valid device model and design strategy to realize the versatile optoelectronics, including the anti-ambipolar transistor and polarimetric photodetectors.
Against the background of a variety of polarized optical applications, a great number of polarization-sensitive photodetectors based on anisotropic two-dimensional (2D) materials and their heterojunctions have been proposed. However, the low polarization ratio (PR), describing the response sensitivity on the polarization angle of the incident light, is still demanding to be solved. In this work, we demonstrate a van der Waals (vdW) Schottky photodiode comprising 2D semiconductor InSe and semimetal 1T′-MoTe2 for the linearly polarized photodetection. The device exhibits obvious photovoltaic characters with a maximum open circuit voltage (Voc) of 0.51 V and fill factor (FF) up to 0.78, which is the highest value in the vdW heterojunction-based photovoltaic device. Due to the anisotropic in-plane structure of 1T′-MoTe2, our photodiode also shows a strong polarization-sensitive photodetection with a PR value up to ∼22, enabling the practical applications in angle-dependent photodetector and image sensors. This work reports a vdW Schottky heterojunction for polarized photodiode with high FF and polarization ratio, toward the polarization-dependent photovoltaic applications.
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