Lattice relaxation process and crystallographic tilt in GaP layers grown on misoriented Si(001) substrates by metalorganic vapor phase epitaxy

A lattice relaxation process and a crystallographic tilt in GaP layers grown on misoriented Si(001) substrates by metalorganic vapor phase epitaxy were investigated. Strained pseudomorphic GaP layers without defects on Si were successfully achieved by the optimization of growth conditions. Below critical thickness, the strained GaP layers were tilted in the misoriented direction of the Si substrates and triclinically distorted. Above critical thickness, the residual strain in the GaP layers was progressively relaxed with increased thickness of the GaP layers by forming 60° misfit dislocations propagating to the two orthogonal <110> directions at the heterointerface. X-ray diffuse scattering around the symmetrical GaP(004) diffraction was observed after introducing misfit dislocations. Diffuse scattering became dominant with an increase in the density of the misfit dislocations and resulted in a broadening of the full width at half maximum of the x-ray rocking curves. The GaP layers that were relaxed with highly dense misfit dislocations were tilted opposite of the misoriented direction due to the imbalance nucleation of the misfit dislocations on each {111} glide plane.