ENERGETICS OF ALN THIN-FILMS AND THE IMPLICATIONS FOR EPITAXIAL-GROWTH ON SIC

We present an ab initio study of the energetics of thin films of AIN o n the Si-terminated SiC(0001) surface. We demonstrate the existence of a vacancy-stabilized NAl wetting layer that can be obtained in both t he root 3x root 3 and 2x2 reconstructions through an N-rich deposition of Al and N. We show that the latter reconstruction is compatible wit h a nonabrupt neutral interface which promotes the formation of thick overlayers. Our study of the competition between two-dimensional and t hree-dimensional growth reveals that only large islands(r(c) greater t han or equal to 60 Angstrom) are stable with respect to the initial tw o-dimensional phase.