P-Type Vertical FETs Realized by Using Fermi-Level Pinning-Free 2D Metallic Electrodes

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Electronics

Background:

• Vertical field-effect transistors (VFETs) in 2D nanomaterial electronics offer ultrashort channel lengths.
• Poor performance in p-type VFETs is attributed to inadequate gate-field-penetrating electrodes and work functions.
• Graphene electrodes (work function ~4.5 eV) are insufficient for optimal VFET characteristics.

Purpose of the Study:

• To enhance p-type VFET performance by replacing graphene with high-work-function electrodes.
• To achieve desired VFET characteristics through improved contact materials.
• To explore the potential of 2D metal-incorporating pseudocomplementary FET structures for device scaling.

Main Methods:

• Fabrication of WSe2-based p-type VFETs utilizing van-der-Waals contacts.
• Employment of high-work-function 2D metals (2H-TaS2, NbSe2, NbS2) as electrode materials.
• Investigation of Fermi-level pinning suppression to achieve p-type ohmic contact.

Main Results:

• Demonstrated WSe2-based p-type VFETs with a high on/off ratio of approximately 10^5.
• Achieved p-type ohmic contact to the WSe2 channel by using high-work-function 2D metal contacts.
• Successfully fabricated a 2D metal-incorporating pseudocomplementary FET structure.

Conclusions:

• High-work-function 2D metal contacts are crucial for realizing high-performance p-type VFETs.
• The developed VFETs show significant potential for dense integration and reduced device scaling.
• The pseudocomplementary FET structure demonstrates a pathway towards advanced 2D electronic devices.