Effect of Mg on the structure and growth of GaN(0001)
The introduction of Mg during growth of GaN(0001) is known to modify the surface morphology. First-principles total energy calculations were performed to determine the effect of Mg on the structure of the GaN(0001) surface. The relative stabilities of possible Mg-rich reconstructions were determined with respect to those of the clean surface. In very Mg-rich conditions it is proposed that the surface structure comprises ½ to ¾ ML of Mg substituting for Ga in the top layer. The stability of these structures reduces the range of Ga chemical potentials for which the Ga-bilayer is stable and therefore provides an explanation for why the window for smooth growth of GaN is narrowed when Mg is present. A structural model for the 22 reconstruction of the GaN(0001):Mg surface is proposed.
Northrup, J. E. Effect of Mg on the structure and growth of GaN(0001). Applied Physics Letters. 2005 March 21; 86 (12): 122108.