Systematic theoretical investigations of compositional inhomogeneity in InxGa1−xN thin films on GaN(0 0 0 1)

We systematically investigate the compositional inhomogeneity near surface, interface, and dislocation in InxGa1−xN thin films on GaN(0 0 0 1) by using our empirical interatomic potential and the Monte Carlo (MC) method. The compositional inhomogeneity is discussed by evaluating individual contribution such as strain relief at the surface and the interface between InxGa1−xN and GaN with/without misfit dislocations. The empirical potential calculations reveal that the dislocation core energy for bulk InN (1.51 eV) is smaller than that of GaN (1.81 eV). This suggests that In atoms preferentially reside in the lattice sites near the dislocation core in InxGa1−xN. The MC simulation clarifies that In surface segregation is found in InxGa1−xN thin films pseudomorphically grown on GaN(0 0 0 1), where the surface composition of In is greater than that of bulk In composition because of strain relief and bond energy profit of In atoms at the surface. Further MC simulation for the system including both surface and misfit dislocations implies that the In atoms segregate at the surface strongly while In atoms segregate near the misfit dislocations weakly.