Strain and elastic constants of GaN and InN

Abstract The effect of strain on the elastic constants of GaN and InN, elaborating the stain state of pseudomorphically grown heterostructures comprising these materials, is investigated. Towards this direction, density functional theory (DFT) calculations using local density approximation (LDA) are performed for studying the electronic and elastic properties of GaN and InN. This systematic study constitutes the first assessment of the performances of the Christiansen modified pseudopotentials in reproducing the elastic constants of nitride materials. Calculation of the elastic constants is not limited up to the previously reported range of strain variable δ = 0.02 [1] but their dependence on the strain state is investigated in an extended range of strain, up to δ = 0.1, which is the strain in pseudomorphic GaN/InN multiple quantum wells (QWs). The elastic constants C 11 , C 12 , and C 13 are more influenced by the type of applied strain as it is deduced from the interrelated energy density curves. The plateau depicted in the U 2 Energy Density curve over δ = +0.07, in both GaN and InN, could be attributed to the nonlinear behaviour that should be expected in the highly strained GaN/InN heterostructures, and which should affect their electronic properties.