Schottky barrier inhomogeneity caused by grain boundaries in epitaxial Al film formed on Si(111)

Epitaxial Al contacts on Si(111) are fabricated by electron beam evaporation at various substrate temperatures around 250 °C. They are observed by high-resolution transmission electron microscopy. Schottky barrier heights (SBHs) of the contacts are measured using current-voltage and capacitance-voltage methods. In the case of single-crystalline Al film, the SBH does not change and its spatial distribution remains homogeneous up to an annealing temperature of 550 °C. In contrast with this, for an epitaxial Al film containing grain boundaries, the spatial distribution of the SBH becomes inhomogeneous above 400 °C. This is attributed to Si diffusion along the grain boundaries in the Al film.