A study of Schottky barrier formation for Ga/Si(111)-(2×1) and Sb/Si(111)-(2×1) interfaces

Abstract

We have studied the Schottky barrier formation of Ga/Si(111)-(2×1), Sb/Si(111)-(2×1) and Sb/GaAs(110) interfaces via photoemission measurements of the following coverage-dependent quantities: the Fermi level position at the interface relative to the valence band maximum Ev (i.e., p-type Schottky barrier ΦBP), work function, Si bulk and surface 2p core level binding energies, Ga 3d and Sb 4d core level energies, and Si surface states. Using a lightly-doped (∠15 Ω cm) p-type Si(111)-(2×1) sample which was cleaved with a single-domain (2×1) surface structure, we observe large deviations from the ’’1/3 band gap-rule’’ for p-type Schottky barriers ΦBP with both Ga and Sb; i.e., ΦBP ? 0.07 eV for Ga/Si(111) and ΦBP ? 0.66 eV for Sb/Si(111). The core level spectra for Ga and Sb for coverages in the 0.3 – 12 Å range show very sharp core levels (observed FWHM ∠0.4–0.5 eV), indicative of a ’’simple’’ interface without complex multiple binding sites or displacive reactions; this is in contrast with our studies of the Sb/GaAs(110) interface, for which the Sb core levels are significantly broadened (∠1 eV FWHM). These studies are discussed in view of current models of Schottky barriers on covalent semiconductors.