Reflectance anisotropy and reflection high-energy electron diffraction intensity oscillations during gas source molecular beam epitaxy growth of Si and SiGe on Si(001)

Abstract

Dynamic reflectance anisotropy (RA) and reflection high-energy electron diffraction (RHEED) intensity measurements were used to study the epitaxial growth of Si and SiGe on Si(001) using gas source molecular beam epitaxy (GSMBE). Oscillatory behaviour in the RA response was observed using a HeNe laser at 1.96 eV during growth of Si and SiGe over a wide range of temperatures. Whilst the surface retains a two domain (1 × 2) + (2 × 1) reconstruction during growth, the period of the RA oscillations corresponds to the time required for the growth of two monolayers (ML). Simultaneous RHEED intensity oscillations observed along the [110] azimuth indicate that the growth proceeds in a ML mode and that the frequency observed is twice that of the RA oscillations. This oscillatory behaviour of the RA response is explained in terms of the varying dimer concentrations along the two orthogonal 〈110〉 directions and hence the relative coverages of the two domains. Comparisons are made between the RHEED and RA oscillations to explain the significance of the RA response.