First-principle study on GaN epitaxy on lattice-matched ZrB2 substrates

We theoretically investigate GaN epitaxy on ZrB2 substrates by clarifying the atomic and electronic structures of GaN/ZrB2 interfaces by first-principle calculations. Both the GaN epitaxial layer and the ZrB2 substrate almost maintain the bulk structures when the epitaxial growth begins with the formation of N–Zr bonds. On the other hand, a remarkable zigzag structural change, which seems to deteriorate the lattice-matched nature of ZrB2 substrates, is found in the interfacial B plane when B–N bonds are formed at the interface. These results indicate that suppression of the B–N bond formation is a key point for the effective use of ZrB2 as a substrate of GaN. We also estimate the Schottky barrier heights of these interfaces. The calculated p-type Schottky barrier height of the interface which contains three N–Zr bonds is small enough to form ohmic contacts.