Misfit evolution in the early stages of the heteroepitaxial growth of GaAs on Si(001): An in-situ X-ray scattering study

Abstract

Abstract The first stages of the GaAs/Si (001) heteroepitaxy are studied by grazing incidence X-ray diffraction on layers grown in-situ by molecular beam epitaxy (MBE). The investigated thicknesses range from 5 to 60 A. The 3D island growth mode has been confirmed for crystalline GaAs nucleated on an As passivated Si(001) surface. A fully coherent interface between GaAs and Si is not observed since a mismatch of 1.55% is already measured after an equivalent deposit of 1.5 molecular layer (ML). On the other hand, complete plastic relaxation leading to the 4% bulk mismatch is not reached after deposition of 20 ML (56 A) and evidence for a lattice parameter gradient normal to the interface is given. Conversely, a quasi 2D growth mode is inferred in the 5–20 A thickness range after in-situ crystallization of a thin (1.5 ML) amorphous GaAs prelayer.