The electronic structure, geometry and energetics of Ga vacancy pairs and N vacancy pairs in both wurtzite and zincblende GaN are investigated via molecular dynamics (MD) simulations using an empirical tight-binding (TB) model with total energy capabilities and supercells containing up to 216 atoms. Our calculations suggest that, by pairing, N vacancies, which in isolation act as shallow donors, can lower their collective formation energy by about 5 eV. In doing so, however, these N vacancies lose their shallow-donor character as the lattice relaxes in response to this aggregation. Contrasting with the N vacancies, the Ga vacancies are found to retain their isolated shallow acceptor behavior and do not gain significant energy upon aggregation. The possible implications for larger aggregate defects are discussed.
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This work was supported in part by the US Office of Naval Research under grant number N00014-96-1-0189. One of the authors (DB) would also like to acknowledge assistance from the King's College Faculty Development Fund.
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Boucher, D.E., Gál, Z.A., DeLeo, G.G. et al. Simulation of Vacancy Pairs in GaN Using Tight-Binding Molecular Dynamics. MRS Online Proceedings Library 482, 73–78 (1997). https://doi.org/10.1557/PROC-482-941