First-principles studies of GaN(0001) heteroepitaxy on ZrB2(0001)

We conduct first-principles total-energy density functional calculations to study the heteroepitaxial growth behavior of GaN(0001) on ZrB2(0001) substrates. Using repeated free-surface terminated slabs, our calculated surface energies suggest that the ZrB2(0001) surface is Zr terminated. The relative stability of six different models of the GaN(0001)/ZrB2(0001) interface is examined as a function of the chemical potentials of Ga and Zr, and the most favorable interface consists of tetrahedrally coordinated N with one Ga-N bond and three N-Zr bonds. This interface structure gives rise to N-polarity in the GaN epitaxial film. Both of these findings agree with previously reported experimental results.