Strain effect on the electronic properties of III-nitride nanosheets: Ab-initio study

In this study the structural and electronic properties of III-nitride monolayers XN (X=B, Al, Ga and In) under different percentages of homogeneous and shear strain are investigated using the full potential linearized augmented plane wave within the density functional theory. Geometry optimizations indicate that GaN and InN monolayers get buckled under compressive strain. Our calculations show that the free-strains of these four monolayers have an indirect band gap. By applying compressive biaxial strain, a transition from indirect to direct band gap occurs for GaN and InN, while the character of band gap for BN and AlN is not changed. Under tensile strain, only BN monolayer behaves as direct band gap semiconductor. In addition, when the shear strain is applied, only InN undergoes an indirect to direct band gap transition. Furthermore, the variations of band gap versus strain for III-nitride monolayers have been calculated. When a homogeneous uniform strain, in the range of [-10%, +10%], is applied to the monolayers, the band gap can be tuned for from 3.92 eV to 4.58 eV for BN, from 1.67 eV to 3.46 eV for AlN, from 0.24 eV to 2.79 eV for GaN and from 0.60 eV to 0.90 eV for InN.