Atomic structure of [0001] tilt boundaries in GaN

Crystals of GaN grown by molecular-beam epitaxi on (0001) sapphire show [0001] tilt boundaries of low and high angles (V. Potin et al., Physical Review B, 61, 5587 (2000)). The structure of these boundaries plays a role in the optoelectrical properties shown by this semiconductor. In this work we have studied the atomic structure of Sigma7, Sigma13 and Sigma19 boundaries (in the coincidence side lattice notation) by means of atomic computer simulation using a modified version of the empirical Stillinger-Weber interatomic potential. For each Sigma boundary we studied the interface of lowest period and found the atomic structure of minimum energy by applying the method of quasidynamic relaxation. Special attention has been paid to the Sigma13 where we have studied two different interfaces comparing our results with the experimental results obtained in a study of bicrystals of ZnO (A.N. Kiselev et al., Phil. Mag. A, 76, 633 (1997)). In these boundaries the atomic structure can be understood in terms of edge dislocations located along the boundary. The (a) over right arrow edge dislocation in GaN has been studied with the same potential and the stable structures are presented here for comparison.