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Multicolor and polarization photodetectors based on heterojunctions, aiding polarization imaging and optical communication applications

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Multicolor and polarization imaging technology can efficiently and accurately identify targets in complex environments, having significant application value in fields such as autonomous driving, security monitoring, and optical communication. Traditional optoelectronic detection systems rely on optical components such as polarizers and gratings and complex architectures to achieve multicolor and polarization detection, which limits device miniaturization and high-density integration. Two-dimensional (2D) van der Waals (vdW) heterostructures, formed by vertically stacking individual 2D materials, offer a promising solution to these challenges. The layered structure and absence of dangling bonds on the surface of 2D materials allow for easy exfoliation and restacking, without the limitation of lattice mismatch. Furthermore, the excellent structural and physical properties of the constituent materials, along with interfacial interactions, enable 2D heterostructures to exhibit synergistic and complementary functions. However, due to the planar isotropic optical and electrical properties of these materials, polarization-sensitive photodetection cannot be achieved by the materials themselves, requiring the introduction of anisotropic structures or external optical components. In recent years, by combining 2D anisotropic semiconductors with other 2D materials, researchers have realized van der Waals heterostructures that simultaneously possess broadband and polarization-sensitive photodetection.

According to MEMS Consulting, a research team from the Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, and the University of Electronic Science and Technology of China recently proposed a multicolor and polarization-sensitive photodetector based on the α-In₂Se₃/2H-MoTe₂ van der Waals heterostructure, which exhibits excellent photodetection performance in the visible and near-infrared (NIR) spectral range. The heterostructure shows a peak responsivity of 3.7 A/W, a specific detectivity of 5.1 × 10⁹ Jones, an external quantum efficiency of 486%, and a response time of approximately 6 ms at a near-infrared wavelength of 940 nm. Furthermore, the heterostructure achieves polarization ratios of 1.40 and 1.07 at wavelengths of 638 nm and 1550 nm, respectively, enabling high-resolution polarization imaging and serving as an optical signal receiver for high-fidelity and encoded optical communication. By leveraging the intrinsic material properties and external field modulation capabilities of van der Waals heterostructures, a promising path is provided for the next generation of high-performance multifunctional photodetectors. This research, titled “Multicolor and Polarization-Sensitive Photodetection of α-In2Se3/2H-MoTe2 vdW Heterostructure for Imaging and Optical Communication,” was published in the journal ACS Applied Materials & Interfaces.

α-In₂Se₃ exhibits planar anisotropic photoresponse characteristics, while 2H-MoTe₂ possesses broadband optical absorption in the near-infrared band. The combination of these two enables the heterostructure to achieve multicolor and polarization-sensitive photodetection. In the experiment, 2D α-In₂Se₃ and 2H-MoTe₂ nanosheets were prepared by mechanical exfoliation and manually stacked to form a van der Waals heterostructure. Figure 1 shows the structure and characterization of the α-In₂Se₃/2H-MoTe₂ van der Waals heterostructure.

Subsequently, researchers determined the work functions of α-In₂Se₃ and 2H-MoTe₂ to be 4.62 eV and 4.68 eV, respectively, using ultraviolet photoelectron spectroscopy (UPS). Based on this, it was calculated that a type-II band alignment formed at the heterojunction interface. The heterostructure exhibited broadband optical absorption characteristics in the visible to near-infrared spectral range, and achieved efficient photodetection performance at a wavelength of 940 nm. The relevant research results are shown in Figure 2.

Researchers further investigated the photoresponse mechanism of the device using a scanning photocurrent microscope at 638 nm, 940 nm, and 1550 nm, with relevant results shown in Figure 3. The results indicate that at 638 nm and 940 nm wavelengths, photogenerated carriers are effectively separated in the heterojunction region, while at 1550 nm, the photoresponse is relatively weak due to weaker absorption. Furthermore, the heterostructure exhibits polarization-sensitive characteristics at 638 nm and 1550 nm wavelengths, with polarization ratios of 1.40 and 1.07, respectively. The relevant results are shown in Figure 4.

To verify the polarization imaging and optical communication capabilities of this heterostructure photodetector, researchers conducted polarization imaging and ASCII code transmission experiments, respectively. The relevant experimental setup and results are shown in Figure 5. Experimental results show that the detector can achieve high-resolution polarization imaging and accurately receive and decode optical signals, demonstrating its application potential in the fields of imaging and optical communication.

In summary, this research achieved multicolor and polarization-sensitive photodetection by constructing an α-In₂Se₃/2H-MoTe₂ van der Waals heterostructure, exhibiting excellent photodetection performance at a wavelength of 940 nm. The heterostructure demonstrates polarization-sensitive characteristics at 638 nm and 1550 nm wavelengths, enabling high-resolution polarization imaging and optical communication. By utilizing the intrinsic material properties and external field modulation capabilities of van der Waals heterostructures, a promising solution is provided for the next generation of high-performance multifunctional photodetectors.

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Single-layer achromatic diffractive optical waveguide in AR glasses

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