Ultrashort Channel Length Black Phosphorus Field-Effect Transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Black phosphorus (BP) is a promising two-dimensional material for next-generation electronics.
• Scaling down transistors to nanometer dimensions is crucial for advancing computing power.
• Achieving high performance and stability in ultrathin BP transistors remains a challenge.

Purpose of the Study:

• To report the fabrication of high-performance top-gated black phosphorus field-effect transistors (FETs) with ultrashort channel lengths.
• To investigate the impact of channel length scaling on device performance and short-channel effects.
• To assess the ambient stability of encapsulated BP FETs.

Main Methods:

• Facile angle evaporation technique for reproducible fabrication of BP FETs with channel lengths from 20 to 70 nm.
• Utilizing black phosphorus as the active channel material in a top-gated configuration.
• Passivation with Al2O3 gate dielectric to enhance chemical stability.

Main Results:

• Successfully fabricated top-gated BP FETs with channel lengths down to 20 nm.
• Achieved respectable on-state current (174 μA/μm) and transconductance (70 μS/μm) at VDS = 0.1 V for 20 nm devices.
• Demonstrated small short-channel effects and a decent on-off current ratio (10^2) even at 20 nm channel length.
• Observed stable device performance without noticeable degradation after one week of ambient storage, attributed to Al2O3 passivation.

Conclusions:

• Atomically thin black phosphorus holds significant promise for the development of ultimately scaled transistors.
• The facile angle evaporation method offers precise control over channel length for nanometer-scale devices.
• Al2O3 passivation effectively enhances the ambient stability of black phosphorus transistors, crucial for practical applications.