Strain Tunable Band-gaps of Two-dimensional Hexagonal BN And AlN: An FP-(L)APW+lo Study

TL;DR

This study uses density functional calculations to explore how in-plane biaxial strain can tune the band gaps of 2D hexagonal BN and AlN, revealing strain-dependent direct and indirect band gap transitions.

Contribution

It provides new insights into the strain-dependent electronic properties of 2D h-AlN, which was not previously reported, complementing existing knowledge on h-BN.

Findings

2D h-BN's band gap becomes indirect under compressive strains below 1.53%

2D h-BN remains direct under tensile strains up to 10%

2D h-AlN's band gap remains indirect for strains up to ±10%

Abstract

Using full potential density functional calculations within local density approximation (LDA), we found strain tunable band gaps of two-dimensional (2D) hexagonal BN (h-BN) and AlN (h-AlN) by application of in-plane homogeneous biaxial strain. The direct band gap of 2D h-BN turns indirect for compressive strains below 1.53% and remains direct under tensile strains up to 10%. However, the band gap of 2D h-AlN remains indirect for strains up to $\pm10%$. While our result on 2D h-BN corroborates the reported strain effect on 2D h-BN (based on pseudo-potential method), our result on the strain tunable band gap of 2D h-AlN is something new. These results may find application in fabrication of future nano-electromechanical systems (NEMS) based on 2D h-BN and h-AlN.