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

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 E_v (i.e., p‐type Schottky barrier Φ_B^P), 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 Φ_B^P with both Ga and Sb; i.e., Φ_B^P ? 0.07 eV for Ga/Si(111) and Φ_B^P ? 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.