Structural properties of cubic GaN epitaxial layers grown on β-SiC

Abstract

Self-consistent tight-binding total energy calculations are performed to study the deposition of a few layers of cubic GaN on (100) β-SiC substrates. Cohesion energies, atomic displacements, dangling bond occupancies and surface reconstructions are calculated for a variety of epitaxial systems including monolayers of either Ga or N as well as single and double bilayers of GaN on either Si or C terminated substrates. The SiC substrates and Ga-N epitaxial layers are represented by 2×2 supercells of 9 Si and C monolayers plus the respective number of monolayers of Ga and N atoms. Depending on the system, surface atoms dimerize either symmetrically or asymmetrically resulting in either 2×1, c-2×2, or 2×2 surface reconstructions. At the substrate-epitaxial-layer interfaces, N binds stronger than Ga to either Si or C. Interface mixing is found to be energetically not advantageous for both C- and Si-terminated substrates, although for the latter the obtained small energy differences may suggest the possibility of mixing.