Effects of the Formation Method of Early GaP Buffer Monolayers on the Strain State of GaAs Films on Vicinal Si(001) Substrates
A significant dependence of the strain state of GaAs film lattice grown by molecular-beam epitaxy (MBE) on the nucleation method of early GaP buffer layers (50 nm) on the vicinal substrate Si(001) 4° around the <011> axis was discovered. GaP growth started layer-by-layer with a gallium or a phosphorus sublayer. If GaP nucleated with a gallium sublayer, the GaAs film has a significant lattice rotation around the <011> axis. If the buffer starts forming with a phosphorus layer the GaAs film evidently rotates around the <001> axis. The film relaxation degree exceeds 100%, and the film is in a laterally strained state. Analysis was carried out using the triclinic distortion model. A reciprocal space scattering map was obtained using X -ray diffraction in a three-axis low resolution setup. The map clearly shows that the GaAs film lattice is rotated.