X-ray scattering study of lattice relaxation in ErAs epitaxial layers on GaAs

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Abstract
We present the results of a high-resolution x-ray scattering study of the lattice relaxation in [001]ErAs epitaxial layers grown on [001]GaAs. Three thickness regimes are found. ErAs is pseudomorphic on GaAs for thicknesses below 70 Å and between 70 and 300 Å lattice relaxation is observed concomitant with an increase of the in-plane mosaic due to the formation of misfit dislocations. Above 300 Å, the out-of-plane transverse scattering from the ErAs lattice planes is no longer specular and further relaxation appears to be related to the out-of-plane mosaic. The ratio of elastic constants, C12/C11, is measured to be 0.126. Thin-film interference oscillations are observed and modeled, finding that for 140 Å of ErAs the interface fluctuations are ∼2.5 monolayers. ErAs/GaAs is an ideal system for x-ray scattering studies of lattice relaxation and structure in epitaxial layers.