Molecular dynamics simulation of cubic InxGa(1-x)N layers growth by molecular beam epitaxy

Abstract

The epitaxial growth of cubic InxGa1-xN layers on GaN (0 0 1) buffer substrates is investigated using molecular dynamics simulation. The substrate temperature, flux ratio of In, Ga, and N, In concentration, and thermal annealing post-growth were simulated and studied. The dislocation, the critical thickness, and the incorporation of the hexagonal phase into the cubic structure for InxGa1-xN are discussed in detail. Theoretical model conditions were simulated by Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) free-source code; the simulated growths reproduce the experimental thermodynamic conditions for molecular beam epitaxy process during the nucleation and first layers deposited. We consider the Stillinger-Weber In-Ga-N-system potentials. We apply time-and-position-dependent boundary constraints that vary the ensemble treatments of the near-surface solid-phase and the bulk-like regions of the growing layer. The results demonstrate that the simulations are suitable for reproducing the experimental epitaxial growths of cubic phase InGaN alloys with In concentration with 0 < x < 0.5. The hexagonal inclusion is a maximum of 5% for In < 0.2, indicating a preferential pure cubic structure. For In >0.2, the RMS roughness surface increase due to the inclusion of hexagonal planes parallel (1 1 0), (1 1 1), and (1 1 2) in cubic matrix. The average error for cubic phase percentage in the InGaN layers is <1% for x < 0.3, whereas for x = 0.48, the error is 4.8% compared with experimental results.