First-principle local density functional calculations are used to determine the equilibrium atomic geometry and associated Schottky barrier height at the ideal Al/GaAs(001) interface. The 1.3% lattice mismatch (after 45° rotation of the Al into an epitaxial position) causes a 3% tetragonal distortion of fcc Al grown on a GaAs(001) substrate. There are also substantial interface-localized atomic relaxations from this tetragonal geometry: the Ga–As layer spacing nearest the interface lengthens, while the Al layers near the interface are found to strongly buckle. The interface considered here is composed of an As–Al bond, and the equilibrium As–Al bond length is found to be about 10% larger than that of zincblende AlAs. Calculation of the Schottky barrier heights for the cubic, tetragonal, and buckled-tetragonal geometries shows strong Fermi level pinning: the barrier heights vary by less than 0.1 eV for the various geometries considered. Only interfacial relaxations which change the As–Al interfacial bond length are found to alter the Schottky barrier height.
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Dandrea et al. (1993) studied this question.