Selective Defect Engineering for Gate-Controlled yet Contact-Transparent Bi₂O₂Se Transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) semiconductors are crucial for ultrascaled electronics.
• A key challenge is balancing strong gate control with low-resistance contacts.
• Bismuth oxyselenide (Bi2O2Se) is a promising 2D material with intrinsic self-doping issues.

Purpose of the Study:

• To address the gate-contact trade-off in Bi2O2Se transistors.
• To develop a selective defect-engineering strategy for improved device performance.
• To enable precise carrier-density modulation and enhance device functionality.

Main Methods:

• Low-temperature nitrogen incorporation to passivate selenium vacancies.
• Density Functional Theory (DFT) calculations.
• Scanning Tunneling Spectroscopy (STS).
• Fabrication and characterization of Bi2O2Se field-effect transistors.

Main Results:

• Nitrogen incorporation passivates selenium vacancies via N-Bi bonding, suppressing self-doping.
• Nitrogen acts as an acceptor-like dopant, neutralizing vacancy-induced donor states.
• Fermi level shifts toward midgap, allowing precise carrier modulation and band-like transport.
• Spatially confined nitrogen incorporation converts transistors to enhancement mode.
• Achieved high electron mobility and on/off ratios up to 10^9 with ohmic contacts.

Conclusions:

• Selective defect engineering decouples channel electrostatics from contact properties.
• This approach offers a scalable and thermally stable route for 2D transistors.
• Enables gate-controllable, contact-transparent 2D transistors for integrated logic circuits.