Characterization of the islands nucleation in LPOMVPE grown In_0.2Ga_0.8As/GaAs multilayer in the near substrate/buffer interfacial regions

The investigation of the initial stages of nucleation of In-enriched islands in In_0.2Ga_0.8As/GaAs multilayers grown on top of GaAs or AlAs buffers deposited on GaAs substrates with a miscut of 2° in the vicinity of the [100] azimuthal direction was performed by using X-ray diffraction and transmission electron microscopy techniques. Simulation of the reciprocal space maps relied on the modelling of the strain field resulting from the compositional profile of the nucleated islands, the substrate and buffer morphology. Consideration of both thickness dependent vertical strain gradients and lateral strain gradients on the interfaces and their effect on the intensity patterns near the superlattice peaks and lateral satellites is elaborated. The observed skew vertical correlation of the islands can vary with the increasing number of interfaces.