X‐ray diffraction analysis of buffer layer effects on lattice distortions of strained layer superlattices

Effects of In0.2Al0.8As buffer layers on the lattice distortions of the strained layer superlattices (In0.2Al0.8As)100 Å (GaAs)100 Å (30 periods) have been investigated by x‐ray diffraction. We have found that for the buffer layer thickness hbuff≥5000 Å, the In0.2Al0.8As layers of both buffer layers and superlattices are in a strain‐free state, while GaAs layers of superlattices show large tetragonal lattice distortions. This fact implies that for hbuff≥5000 Å, buffer layers dominate the strain fields of superlattices, i.e., buffer layers play the role of an ‘‘effective substrate.’’ Lattice distortions in buffer layers and superlattices against buffer layer thickness are discussed.