Characterizing Defects Inside Hexagonal Boron Nitride Using Random Telegraph Signals in van der Waals 2D Transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Single-crystal hexagonal boron nitride (hBN) is critical for 2D electronic and quantum devices.
• Defects in hBN significantly influence device performance, necessitating characterization and engineering.

Purpose of the Study:

• To investigate defect capture and emission dynamics in hBN using low-frequency noise (LFN) spectroscopy.
• To identify the atomistic origin of defects in hBN within a heterostructure.

Main Methods:

• Utilized LFN spectroscopy on hBN-encapsulated MoS2 field-effect transistors (FETs).
• Analyzed gate bias- and temperature-dependent LFN data to detect random telegraph signals (RTS).
• Performed multispace density functional theory (MS-DFT) calculations on a defective hBN/MoS2 heterostructure model.

Main Results:

• Detected RTS from a single trap species in hBN within large-area (100 μm²) devices at cryogenic temperatures.
• Identified substitutional carbon atoms on boron sites as the atomistic origin of RTS.
• Demonstrated LFN spectroscopy's effectiveness in characterizing hBN defects.

Conclusions:

• Substitutional carbon defects in hBN are identified as a source of noise in MoS2 FETs.
• LFN spectroscopy combined with MS-DFT analysis is a powerful tool for atomic-level defect characterization in hBN.
• This approach facilitates defect engineering for enhanced 2D device performance.