The mechanical properties and strain effect on the electronic properties of III-nitride monolayers: ab-initio study

We firstly investigate the mechanical properties of III-N (III = B, Al, Ga, In) monolayers and find that the stiffness constant, Young's modulus, Shear modulus would decrease while the Poisson's ratio would increase with the increase of cation radius. Additionally, the band structure, projected density of states and band edges under biaxial, uniaxial and shear strain range from -2% to 2% are studied in detail, we found the band gap of GaN and AlN could be tuned by uniaxial and biaxial strain more linearly than that of BN and InN. The shear strain is found to hardly affect the band gap value for III-N monolayers, the compressive strain would tune the gap type of BN(InN) from direct (indirect) into indirect (direct) but not the case of AlN and GaN. We find that the heterojunction types can be tuned by biaxial strain which would be applied in the fabrication of optoelectronic devices.