Atomic force microscopy and scanning tunneling microscopy studies of large-scale unstable growth formed during GaAs(001) homoepitaxy

Atomic force and scanning tunneling microscopy studies have been performed on GaAs(001) films grown by molecular beam epitaxy. Multilayered mounds are seen to evolve when the growth conditions favor island nucleation. As the epilayer thickness is increased, these features grow in all dimensions but the angle of inclination remains approximately constant at 1°. The mounding does not occur on surfaces grown in step flow. We propose that the multilayered features are due to an unstable growth mode which relies on island nucleation and the presence of a step edge barrier.