GaN/LiNbO3 (0 0 0 1) interface formation calculated from first-principles

The stable adsorption sites for both Ga and N ions on the ideal and on the reconstructed LiNbO3 (0 0 0 1) surface are determined by means of first-principle total energy calculations. A single N layer is found to be more strongly bound to the substrate than a single Ga layer. The adsorption of a GaN monolayer on the polar substrate within different orientations is then modeled. On the basis of our results, we propose a microscopic model for the GaN/LiNbO3 interface. The GaN and LiNbO3 (0 0 0 1) planes are parallel, but rotated by 30image each other, with in-plane epitaxial relationship [1 0image 0]GaN‖ [1 1 image 0]LiNbO3. In this way the (0 0 0 1) plane lattice mismatch between GaN and LiNbO3 is minimal and equal to 6.9% of the GaN lattice constant. The adsorbed GaN and the underlying LiNbO3 substrate have parallel c-axes.