Reflectance anisotropy spectroscopy and reflection high-energy electron diffraction of submonolayer coverages of Si grown on GaAs(001) by molecular-beam epitaxy.

The techniques of reflectance anisotropy spectroscopy (RAS) and reflection high-energy electron diffraction (RHEED) have been employed in concert to characterize the growth of submonolayer coverages of Si deposited onto GaAs(001) substrate crystals. The RHEED observations enabled the RAS spectra collected for a series of Si coverages in the range 0.005--1.000 ML to be interpreted in terms of changes in the sample surface structure. The following series of surface reconstructions evolved with increasing Si coverage from 0 to 1 ML: c(4\ifmmode\times\else\texttimes\fi{}4), c(4\ifmmode\times\else\texttimes\fi{}4)/(1\ifmmode\times\else\texttimes\fi{}2), (1\ifmmode\times\else\texttimes\fi{}2), (1\ifmmode\times\else\texttimes\fi{}2)/(3\ifmmode\times\else\texttimes\fi{}1), and (3\ifmmode\times\else\texttimes\fi{}1). The fact that unique, but highly reproducible, RAS signatures were obtained for each of these surface phases demonstrates the applicability of a combined RHEED-RAS system for monitoring submonolayer heteroepitaxial growth with a surface sensitivity of the order of 1/200 of a monolayer.