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

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.