The behaviors of Ga and N vacancies (Schottky defects, Frenkel defects), lattice-site and interstitial Mg atoms, and interstitial H atoms were studied in wurtzite-type crystals by using molecular dynamics simulations. The parameters for a 2-body interatomic potential were determined by using the Hartree-Fock ab initio method. When there were Schottky defects, the Ga and N vacancies were often paired and the paired vacancies repeatedly formed and disappeared during the simulation. When there were Frenkel defects, interstitial Ga or N atoms became lattice-site ones via the substitutional-interstitial mechanism. The lattice-site Mg atom exhibited a very stable behavior, stayed there for a long period and underwent thermal vibrations. The interstitial Mg atom was in a semi-stable state at the cage center of an hexagonal crystal structure. The Mg atom underwent thermal vibration there, then hopped from one cage center to an adjacent one. The diffusivity of interstitial Mg atoms on the (00▪1) plane was predominant when compared with the diffusivity along the [00▪1] direction.

Molecular Dynamics of Magnesium Diffusion in Wurtzite-Type GaN Crystal. K.Harafuji, T.Tsuchiya, K.Kawamura: Japanese Journal of Applied Physics–1, 2004, 43[2], 522-31