THE STRAIN-ENERGY DENSITIES OF HEXAGONAL AND TETRAGONAL EPITAXIAL MEDIA

Motivated by the burgeoning interest in the epitaxial growth of hexago nal and tetragonal semiconductors, we report expressions for the strai n energy density for the high symmetry directions in these crystal sys tems. In addition, we have calculated tile behaviour of the strain ene rgy density as a function of epilayer surface normal orientation for t he following systems: GaN on 6H-SiC, GaN on AlN, AlN on 6H-SiC and CuI nSe2 on GaAs. For the first three cases, we suggest that substrate ori entations not yet investigated may improve film quality as they will s erve to reduce the strain energy density by approximately 30%, 17% and 65%, respectively, relative to the commonly employed (001) substrate orientation.