Depth profiles of perpendicular and parallel strain in a GaAsxP1−x/GaP superlattice

Using double-crystal x-ray rocking curves, depth profiles of parallel and perpendicular strain were obtained in a GaAs0.14P0.86/GaP superlattice grown on a buffer layer on (100) GaP. Combining symmetric Fe Kα1 (400) and asymmetric Cu Kα1 (422) reflections, a constant parallel strain of 0.19% relative to the substrate was found throughout the superlattice and buffer layer. Relative to the substrate, the perpendicular strain was found to be 0.26% in the buffer, and 0.80% and −0.19% in the 176-Å-thick superlattice GaAsxP1−x and GaP layers, respectively. The strain profiles indicate the buffer is ∼80% decoupled from the substrate by misfit dislocations near the buffer/substrate interface, and the lattice misfit in the superlattice is elastically accommodated by the epitaxial structure with a small shift in the average lattice constant relative to the equilibrium superlattice structure.