Schottky Barriers in Bilayer Phosphorene Transistors.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Work function approximation (WFA) is unreliable for evaluating Schottky barrier height (SBH) in monolayer (ML) 2D material field-effect transistors (FETs) due to Fermi-level pinning.
• Previous studies primarily focused on ML 2D materials, leaving bilayer (BL) systems less explored.

Purpose of the Study:

• To systematically investigate Schottky barrier formation in bilayer (BL) phosphorene FETs.
• To develop a more accurate method for estimating SBH in 2D material-based transistors with strong electrode interactions.

Main Methods:

• Utilized ab initio electronic band calculations and quantum transport simulation (QTS).
• Investigated interfaces between BL phosphorene and various metals (Al, Ag, Cu, Au, Cr, Ti, Ni, Pd).
• Differentiated between vertical and lateral Schottky barriers (SBs) and their respective characterization methods.

Main Results:

• Identified two types of SBs in BL phosphorene FETs: vertical (energy band analysis) and lateral (QTS).
• Demonstrated that vertical SBHs correlate better with ML FET QTS results than WFA.
• Achieved good agreement between theoretical predictions and experimental data for SBH and contact polarity.

Conclusions:

• Developed a more general method than WFA for estimating lateral SBHs in ML semiconductor transistors based on BL phosphorene analysis.
• Provided crucial insights into BL phosphorene-metal interfaces for device design.
• Successfully predicted n-type and p-type Schottky contacts with specific SBHs for various electrode materials.