Magnesium incorporation at (0001) inversion domain boundaries in GaN

First-principles pseudopotential density functional calculations have been performed for Mg-rich inversion domain boundaries that form on (0001) planes in GaN. These types of boundaries separate inverted material from the host matrix in the pyramidal inversion domain defects reported to exist in heavily Mg-doped GaN. The model of the boundary proposed on the basis of these total energy calculations exhibits GaNMgNGa layers that are stacked in abcab registry, with at least 3/4 of the available c sites occupied by Mg atoms. An additional 1/4 monolayer of Mg can be incorporated in this layer provided additional compensating Mg acceptors are located nearby. A significant fraction of the Mg present in heavily doped material may reside in these boundaries.