GROWTH MODE AND INTERFACE FORMATION OF SB ON GAAS(100)

The growth of thin Sb layers on GaAs(100) was studied in ultra high va cuum by means of Raman scattering and spectroscopic ellipsometry. Clea n (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 be tween 20 and 30 monolayers (ML). For larger coverages the E(g) and A1g phonon modes of crystalline Sb are detected indicating the crystallis ation of the overlayer. After the crystallisation, the LO phonon mode of the GaAs substrate is substantially broadened. The structural trans ition of the Sb is also reflected in changes in the imaginary part of the dielectric function epsilon(omega) obtained by ellipsometry. Both the LO broadening and the changes in epsilon(omega) can be interpreted by a transition to a metallic Sb overlayer. Crystalline overlayers be low 20 ML thickness showing a metallic like dielectric function can be obtained by annealing amorphous Sb overlayers to approximately 180-de grees-C.