High quality epitaxial Si films onto γ-Al2O3 (111)/Si (111) substrates using Al predeposition layers

Abstract

Very flat epitaxial Si(111) films with high crystalline quality were grown using thin Al layers deposited onto γ-Al2O3 (111)/Si (111) substrates at room temperature, prior to the growth of Si films by Si2H6 gas source molecular beam epitaxy. Epitaxial Si layers grown with a 10-Å-thick Al predeposition layers showed 7×7 streaked reflection high-energy electron diffraction patterns and a mirrorlike surface. The epitaxial Si layer had a significantly improved crystalline quality and surface morphology comparable to that grown without the Al predeposition layer. The optimum Al thickness for a high quality Si film was 5–10 Å, even though the thickness was varied from 0 to 25 Å. The Al deposited surface was changed to an Al–O surface (rather than a metallic Al layer) just before Si growth at 800 °C, and a decrease in the incubation time was observed for an Al thickness of 5–10 Å. It is believed that a modification of the Al2O3 surface occurs, which results in improved crystalline quality of Si films grown on the Al2O3.