Self‐consistent tight‐binding total energy calculations are performed to study the deposition of a few layers of cubic GaN on (100) &bgr;‐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. ©1996 American Institute of Physics.