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Model of the surface. In this structure of the Ga atoms in the top of the last double layer of GaN have been replaced by Mg atoms. The structure shown here has ML of Mg and satisfies the electron counting rule because the dangling bonds of the Mg and Ga are completely empty. The Mg atoms are black, the Ga atoms are white, and the N atoms are grey.
The relative formation energies for Mg induced reconstructions in comparison to three types of clean surface reconstructions. The results correspond to the Mg-rich limit, where equilibrium with is assumed. The chemical potential of Ga varies between and . The calculated value of is . The zero of the energy scale corresponds to the formation energy of the ideal GaN(0001) surface. The inclusion of the Mg induced reconstructions leads to a smaller region of the phase diagram where the Ga-bilayer could be stable.
This plot indicates the energies of the Mg-induced reconstructions in less Mg-rich conditions. In this case . In these less Mg-rich growth conditions both the structure and the structure appear as stable phases depending on the Ga chemical potential.
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