STRUCTURAL-PROPERTIES OF CUBIC GAN EPITAXIAL LAYERS GROWN ON BETA-SIC

Self-consistent Eight-binding total energy calculations are performed to study the deposition of a few layers of cubic GaN on (100) beta-SiC substrates. Cohesion energies, atomic displacements, dangling bond oc cupancies and surface reconstructions are calculated for a variety of epitaxial systems including monolayers of either Ga or N as well as si ngle and double bilayers of GaN on either Si or C terminated substrate s. The SiC substrates and Ga-N epitaxial layers are represented by 2x2 supercells of 9 Si and C monolayers plus the respective number of mon olayers of Ga and N atoms. Depending on the system, surface atoms dime rize either symmetrically or asymmetrically resulting in either 2x1, c -2x2, or 2x2 surface reconstructions. At the substrate-epitaxial-layer interfaces, N binds stronger than Ga to either Si or C. Interface mix ing is found to be energetically not advantageous for both C- and Si-t erminated substrates, although for the latter the obtained small energ y differences may suggest the possibility of mixing. (C) 1996 American Institute of Physics.