LIGHT-SCATTERING AND ELECTRON-MICROSCOPY STUDY OF THE SURFACE-MORPHOLOGY OF GAAS FILMS GROWN BY MOLECULAR-BEAM EPITAXY

The surface morphology of thermally quenched GaAs films grown by molecular beam epitaxy on GaAs substrates has been studied by elastic light scattering, by scanning electron microscopy and by scanning tunneling microscopy (STM) in air. STM shows. that the oxide-desorbed surface of GaAs is pitted, but smooths after deposition of a few hundred nanometers of material. Light scattering shows that, after the surface has smoothed, the power spectral density of the surface approaches a q(-2) dependence on spatial frequency over the spatial frequency range 0.2 mu m(-1) < q < 20 mu m(-1) that is accessible to the light scattering measurements at 488 nm. This result is in agreement with the predictions of dynamical scaling theory in the case where the time evolution of the surface morphology is described by an Edwards-Wilkinson type equation.