Growth-induced interface roughness of GaAs/AlAs-layers studied by X-ray scattering under grazing angles

We have studied GaAs/AlGaAs- and GaAs/AlAs-samples grown by molecular beam epitaxy by X-ray scattering under grazing angles to investigate surface and interface roughness. We discuss the reliability of buried interface roughnesses derived from fits to specular reflectivity by means of a sample series grown at substrate temperatures from 605 to 685°C. Even for samples of high perfection no abrupt interfaces were found. We have applied this method to the problem of growth-induced roughening of GaAs- and AlAs-layers. Sample series with increasing film thickness between 50 and 2000 Å for AlAs and 5000 Å for GaAs have been investigated. We observe roughening which in the case of AlAs does not follow a power law expected within the framework of kinetic roughening theory. However, for GaAs the data can be described by a very small growth exponent β = 0.11 ± 0.03