Two-dimensional anisotropic semiconductors: from structure and properties to device applications

The emergence of two-dimensional (2D) anisotropic semiconductor materials has gained significant interest due to their potential applications in electronic and optoelectronic fields. These materials exhibit in-plane angle-dependent properties owing to their distinct electronic band dispersion along different directions. However, a comprehensive overview of 2D anisotropic semiconductors, ranging from electronic band structures and anisotropic properties to device applications, is still lacking. Therefore, this review systematically summarizes the electronic band structures, optical properties and device applications of 2D anisotropic semiconductors. First, the crystal structures and electronic band structures of typical 2D anisotropic semiconductors are summarized. Next, the characterization of anisotropic electrical and optical properties, including conductance, Raman scattering, photoluminescence, optical absorption and second-harmonic response, is systematically reviewed. Subsequently, the performances of polarized optoelectronic devices based on 2D anisotropic materials, such as polarized photodetectors and imaging systems, is compared and concluded. Finally, the future perspectives of 2D anisotropic materials are discussed and highlighted. Overall, this review provides an opportunity to bridge the gap between the fundamental properties of electronic band structures and optoelectronic device applications based on 2D anisotropic semiconductors. The discussion in this review will promote the scientific frontier for designing novel electronic and optoelectronic devices based on 2D anisotropic semiconductors in the future.