Evidence from the surface morphology for nonlinear growth of epitaxial GaAs films.

The mesoscale morphology of homoepitaxial GaAs surfaces is explained with an anisotropic and nonlinear Kardar-Parisi-Zhang (KPZ) model in which adatoms are incorporated into the film from a metastable surface layer. Evaporation-condensation between the film and the metastable layer is proposed as the microscopic physical origin of the KPZ description, as well as of the excess noise observed in the power spectral density. The parabolic mounds observed experimentally in films grown on rough substrates are in good agreement with the surface shape expected from the solution of the KPZ equation in the large amplitude limit.