Elastic properties of InGaN and InAlN from first-principles calculations

Elastic properties of wurtzite InxGa1−xN and InxAl1−xN alloys are investigated using the first principles calculations. For alloys with uniform distribution of In atoms, a Vegard-like approximation can describe the composition dependences of C12, C13, and C44 in InxGa1−xN, and C12, C13, and C33 in InxAl1−xN, whereas significant sublinear deviations are found for C11and C33 in InxGa1−xN and for C11and C44in InxAl1−xN. These deviations lead to significant changes in determination of strain in InxGa1−xN and InxAl1−xN layers grown coherently on GaN substrates along polar and nonpolar directions. Changes of the interband transitions energy in InxGa1−xN/GaN quantum wells due to the inclusion of the nonlinear dependence of the elastic constants on In content do not exceed 25 meV