Monolayer InSe photodetector with strong anisotropy and surface-bound excitons.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Monolayer indium selenide (InSe) possesses inherent in-plane anisotropy.
• This anisotropy is critical for advanced optoelectronic device functionalities, particularly photodetectors.

Purpose of the Study:

• To investigate the anisotropic quantum transport properties of monolayer InSe in both dark and illuminated conditions.
• To explore the role of surface-bound excitons in generating anisotropic photocurrent.
• To evaluate the potential of InSe for various electronic and optoelectronic applications.

Main Methods:

• Utilized nonequilibrium Green's function density functional theory (NEGF-DFT) for quantum transport calculations.
• Employed time-dependent density functional theory (TD-DFT) to study excitonic effects and photocurrent.
• Analyzed anisotropic transport barriers and exciton contributions from specific orbitals (In 5pz, Se 4pz, Se 4dz2).

Main Results:

• Anisotropic dark quantum transport was observed, with a significant difference between zigzag and armchair orientations (Id-zig/Id-arm = 1.2 × 102).
• Linearly polarized photocurrent calculations yielded a high extinction ratio, reaching a maximum of 105.67.
• Surface-bound excitons, originating from In 5pz, Se 4pz, and Se 4dz2 orbitals, were identified as the primary source of strong anisotropic photocurrent.

Conclusions:

• The in-plane anisotropy of monolayer InSe is strongly influenced by surface-bound excitons, leading to significant anisotropic photocurrent.
• Monolayer InSe demonstrates excellent potential for developing high-performance photodetectors and polarized light devices.
• InSe is a promising material for flexible nanoelectronics, optoelectronics, and field-effect transistors.