Structural properties of GaAs on Si and Ge substrates

Abstract

We report a detailed x-ray scattering study of GaAs grown on Si and Ge substrates by molecular beam epitaxy. We find that the Q dependence of the peak widths can be completely understood in terms of residual strains in the epitaxial film. This result places lower limits on the domain size and antiphase domain size (if they exist) of 6000 and 4000 Å, respectively. In addition, we find that the GaAs lattice is commensurate with that of the Ge substrate, but that the GaAs lattice is incommensurate with the Si substrate; however, in both cases the GaAs lattice has tetragonal symmetry. We show that the measured lattice parameters and thus the tetragonal distortion can be explained by differential thermal expansion for the Si substrate sample.