Diffusion in GaN/AlN superlattices: DFT and EXAFS study

We report theoretical and experimental study of diffusion processes at GaN/AlN interfaces. Using climbing image nudged elastic band method with density functional theory (DFT) we have calculated migration barriers for vacancy-mediated self-diffusion in group-III element sublattice in AlN and GaN, for Ga diffusion in AlN and for Al diffusion in GaN. Attempt frequencies for this diffusion processes have been estimated based on harmonic transition state theory, and Al-Ga interdiffusion coefficient has been calculated. The calculations are in agreement with experimental results for GaN/AlN superlattices obtained by extended X-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy.