Growth mode and interface formation of Sb on GaAs(100)

Abstract

The growth of thin Sb layers on GaAs(100) was studied in ultra high vacuum by means of Raman scattering and spectroscopic ellipsometry. Clean (100) surfaces were prepared by heating As-passivated MBE-grown GaAs substrates. The Raman spectra taken after stepwise Sb deposition show that the overlayer grows in an amorphous structure up to coverages between 20 and 30 monolayers (ML). For larger coverages the E g and A 1g phonon modes of crystalline Sb are detected indicating the crystallisation of the overlayer. After the crystallisation, the LO phonon mode of the GaAs substrate is substantially broadened. The structural transition of the Sb is also reflected in changes in the imaginary part of the dielectric function ϵ(ω) obtained by ellipsometry. Both the LO broadening and the changes in ϵ(ω) can be interpreted by a transition to a metallic Sb overlayer. Crystalline overlayers below 20 ML thickness showing a metallic like dielectric function can be obtained by annealing amorphous Sb overlayers to approximately 180°C.