Stability of Mg-incorporated InN surfaces: first-principles study

InN films are attractive materials for electronic and optelectronic applications. The growth of InN eptitaxial films with $n$-type and $p$-type conductivity has traditionally been performed along the polar $<$0001$>$ direction\footnote{R.E. Jones et al., Phys. Rev. Lett, {\bf 96}, 125505 (2006)}, which may result in large polarization fields along the growth direction, reducing the radiative efficiency of quantum-well light emitters. To overcome this drawback, the growth along nonpolar orientation such as (10$\bar{1}$0) and (11$\bar{2}$0) planes and its $p$-type doping have been recently carried out. We have addressed this issue by performing first-principles pseudopotential calculations for Mg-incorporated InN surfaces in various orientations, including (10$\bar{1}$0) and (11$\bar{2}$0) as well as (0001) and (000$\bar{1}$) surfaces\footnote{J.-H. Song et al., Phys. Rev. Lett. {\bf 101}, 106803 (2008)}. The calculated surface energies demonstrate that qualitative trends in the stability of Mg-incorporated surfaces agree with those on GaN surfaces \footnote{J.E. Northrup, Appl. Phys. Lett. {\bf 86}, 122108 (2005)}, although several surface reconstructions different from those on GaN surfaces are obtained. The effects of growth conditions on $p$-type doping are also discussed.