Role of Interlayer Coupling on the Evolution of Band Edges in Few-Layer Phosphorene

TL;DR

This study uses first-principles calculations to explore how interlayer coupling influences the electronic band edges in few-layer phosphorene, revealing strain sensitivity and a semi-empirical model for band evolution.

Contribution

It introduces a semi-empirical interlayer coupling model that accurately reproduces band-edge evolution in few-layer phosphorene from first-principles data.

Findings

Monolayer phosphorene is an indirect band gap semiconductor.

Band gap can transition from indirect to direct with slight lattice expansion.

Interlayer coupling significantly affects band gap and effective masses.

Abstract

Using first-principles calculations, we have investigated the evolution of band-edges in few-layer phosphorene as a function of the number of P layers. Our results predict that monolayer phosphorene is an indirect band gap semiconductor and its valence band edge is extremely sensitive to strain. Its band gap could undergo an indirect-to-direct transition under a lattice expansion as small as 1% along zigzag direction. A semi-empirical interlayer coupling model is proposed, which can well reproduce the evolution of valence band-edges obtained by first-principles calculations. We conclude that the interlayer coupling plays a dominated role in the evolution of the band-edges via decreasing both band gap and carrier effective masses with the increase of phosphorene thickness. A scrutiny of the orbital-decomposed band structure provides a better understanding of the upward shift of valence band maximum surpassing that of conduction band minimum.