Ultrabroadband Photosensitivity and Frequency-Mixing in Anisotropic Weyl Semimetal NbNiTe₂.

Abstract

Broadband anisotropic photodetectors show great promise for polarization-sensitive imaging and multispectral optoelectronic systems yet face critical challenges in material anisotropy modulation and broadband sensitivity. Weyl semimetals exhibit giant optical anisotropy and tunable heterojunction band alignment, enabling high-performance anisotropic photodetection. Herein, ultrabroadband PDs based on the NbNiTe₂ (niobium nickel telluride), enabled by antenna integration and heterostructure engineering, achieve high sensitivity from visible to Terahertz (THz). Leveraging its topological quantum material properties and antenna integration, NbNiTe₂-based PDs demonstrate high responsivity of 5.86 A/W and fast response time of 0.83 μs in the THz regime. Combined with the nonlinear property of the NbNiTe₂-based PDs, a heterodyne experiment is developed, demonstrating their potential for multifrequency THz signal detection and applicability in complex signal processing. The NbNiTe₂/MoS₂ heterostructure engineered PDs exhibit a remarkably specific detectivity (<i>D</i>*) ranging from 1.37 × 10¹¹ to 4.08 × 10¹¹ cm·Hz^0.5·W^-1 and broad spectral response covering visible to near-infrared (NIR) wavelengths. Meanwhile, these NbNiTe₂-based PDs exhibit significant anisotropic properties, a high electrical conductivity anisotropy ratio of 16.9 and an ultrahigh anisotropy ratio of 5.74. These findings can provide a viable pathway for next-generation room-temperature broadband PDs with high sensitivity and anisotropy.