High-quality silicon/insulator heteroepitaxial structures formed by molecular beam epitaxy using Al2O3 and Si

Heteroepitaxial growth of gamma-Al2O3 films on a Si substrate and the growth of Si films on the gamma-Al2O3/Si structures by molecular beam epitaxy have been investigated. It has been found from AFM and RHEED observations that, gamma-Al2O3 films with an atomically smooth surface with an RMS values of similar to 3 Angstrom and high crystalline quality can be grown on Si (1 1 1) substrates at substrate temperatures of 650-750 degrees C. Al2O3 films grown at higher temperatures above 800 degrees C, did not show good surface morphology due to etching of a Si surface by N2O gas in the initial growth stage. It has also been found that it is possible to grow high-quality Si layers by the predeposition of Al layer followed by thermal treatment prior to the Si molecular beam epitaxy. Cross-sectional TEM observations have shown that the epitaxial Si had significantly improved crystalline quality and surface morphology when the Al predeposition layer thickness was 10 Angstrom and the thermal treatment temperature was 900 degrees C. The resulting improved crystalline quality of Si films grown on Al2O3 is believed to be due to the Al2O3 surface modification. (C) 1999 Elsevier Science B.V. All rights reserved.