Electron Microscopy and X-ray Diffraction determinations of strain release in InGaAs/ GaAs superlattices grown by Molecular Beam Epitaxy

Strain-induced dislocations have been studied in low and medium mismatched (001) oriented InxGa1-xAs/GaAs superlattice heterostructures. Their optical quality, composition, residual strain, dislocation nature, and location have been studied by x-ray diffraction and electron microscopy techniques. Different predictions of the residual strain have been discussed briefly. All the samples presented perpendicular networks of misfit dislocations with different densities along the [110] and [110] directions. The dislocations were confined inside the buffer layer or at the buffer-superlattice interface without threading the superlattice. A symmetric dislocation movement along the [110] type directions were induced by the electron beam in a scanning electron microscope. Panchromatic cathodoluminescence observations allowed the on-line observation of the dislocation movement when thickness and composition were such that a low linear dislocation density (<2 X 10(3) cm-1) was present. The effect was correlated to the different level of metastability of the superlattice. Almost only 60-degrees type misfit dislocations were observed in all the specimens.