Hydrogen and magnesium incorporation on c-plane and m-plane GaN surfaces

The effect of hydrogen on Mg incorporation for both polar and nonpolar GaN surfaces is explored using density functional total energy calculations. A thermodynamic approach is employed, with chemical potentials appropriate for realistic growth conditions. It is shown that hydrogen stabilizes new Mg-rich surface reconstructions for both the (0001) and (10 (1) over bar0) surfaces. Hydrogen greatly enhances the stability of Mg-rich reconstructions of the m plane. Experimental results for p-type doping obtained in growth on both the m-plane and c-plane surfaces can be understood on the basis of these results. A laterally contracted row model for the GaN(10 (1) over bar0) surface is shown to be energetically favorable in Ga-rich conditions.