Electron Microscopy and X‐Ray Diffraction Determinations of Strain Release in InGaAs / GaAs Superlattices Grown by Molecular Beam Epitaxy

Abstract

Strain‐induced dislocations have been studied in low and medium mismatched (001) oriented 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. Asymmetric 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 was present. The effect was correlated to the different level of metastability of the superlattice. Almost only 60° type misfit dislocations were observed in all the specimens.