X-ray scattering studies of interfacial microstructures in In_xGa_1-xAs/GaAs superlattices

Interfacial microstructures in 100-period In_xGa_1-xAs(15angstrom)/GaAs(100angstrom) superlattices grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x-ray scattering techniques. Unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample with x = 0.535 grown at 480°C, indicating an in-plane structural ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the In_xGa_1-xAs layers gives rise to long-range lateral periodic arrays of cluster-like microstructures with spacing on the order of a few hundred Angstroms. This thickness modulation is found to occur only in [110] direction, thus the material can be viewed as a somewhat disordered array of grown-in parallel quantum wires.