Molecular Dynamics of Magnesium Diffusion in Wurtzite-type GaN Crystal

The behaviors of Ga and N vacancies (Schottky defects, Frenkel defects), lattice-site and interstitial Mg atoms, and interstitial H atoms are studied in the wurtzite-type GaN crystal by molecular dynamic simulation. Parameters for a two-body interatomic potential are determined by the Hartree-Fock ab initio method. When there are Schottky defects, Ga and N vacancies are often paired, and the paired vacancies repeatedly form and disappear during the simulation. When there are Frenkel defects, interstitial Ga or N atoms become lattice-site ones by the substitutional-interstitial mechanism. The lattice-site Mg atom shows a very stable state, stays there for a long period and undergoes thermal vibration. The interstitial Mg atom is in a semistable state at the cage center of a hexagonal crystal structure. The Mg atom undergoes thermal vibration there, then hops from one cage center to an adjacent one. The diffusivity of interstitial Mg atoms on the (0001) plane is predominant compared with the diffusivity along the [0001] direction.