Black phosphorus transistors with van der Waals-type electrical contacts

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Schottky barriers impede performance in two-dimensional (2D) material transistors with bulk metal electrodes.
• Contact engineering offers a solution to mitigate these barriers.

Purpose of the Study:

• Investigate van der Waals (vdW)-type electrical contacts for monolayer (ML) black phosphorus (BP) transistors.
• Compare 2D metal contacts and 2D material/bulk metal hybrid contacts.

Main Methods:

• Ab initio energy band calculations.
• Quantum transport simulations.
• Analysis of 2D graphene, borophene, and bulk Ni electrodes.

Main Results:

• 2D graphene and borophene electrodes significantly improve gate electrostatic control in ML BP transistors.
• Subthreshold swing decreased by 30-50%, and on-state current increased 4-7 times compared to Ni contacts.
• Hybrid contacts (graphene/Ni, BN/Ni) showed limited improvement.

Conclusions:

• 2D metal contacts are more efficient than hybrid contacts for improving ML BP field-effect transistor (FET) performance.
• Findings guide the selection of vdW contacts for other 2D transistors.