Epitaxial growth of Al[sub 2]O[sub 3]/Si heterostructures

Abstract

We have performed an investigation into the synthesis of Al2O3/Si heterostructures grown by gas source molecular beam epitaxy. The study has been motivated by the potential of the aluminum oxide as a barrier material for silicon, enabling Si based tunneling resonant diodes, as well as the possibility for a coherent silicon on insulator material with low dislocation density. The films have been grown on Si(111) orientation, in a gas source molecular beam epitaxy chamber equipped with silane, nitrous oxide gas sources, and solid state aluminum cell. The growth temperature was varied between 700 and 900 °C. A silicon thin film has been grown above 950 °C with the source material obtained from cracking of silane gas at the growth surface. The samples were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, Auger electron spectroscopy, and scanning electron microscopy. The films growth rate has been found to be very sensitive to the growth temperature and aluminum flux decreasing rapidly above 700 °C. The films grown on Si(111) substrate are γ-Al2O3, a deficient spinel structure, and are oriented in the (100) direction, which allows for lattice constant matching between the surface nets of silicon and aluminum oxide. This result differs from the one presented by Wado et al. (Ref. Reference 8). The small full width at half maximum of the peaks in the XRD spectra indicates a small mosaic spread and large coherence lengths confirming good crystalline quality.