A study was made of the optimization of the properties of the strained inter-layers which were used to reduce the density of threading dislocations that was generated in an InP layer when grown on GaAs. The effect of each strained inter-layer as a defect-filter was measured, using X-ray diffraction. All of the layers were grown by means of low-pressure metalorganic vapor phase epitaxy. Ternary compounds, such as InGaP and InGaAs, were investigated as materials for strained inter-layers. Firstly, In1-xGaxP was examined by varying its thickness and composition. Layers with an x-value of 0.2, and with a thickness of 40nm, were found to be the most effective. Closer examination of InGaAs revealed that, not only the lattice parameter but also other material properties, affected the way in which the strained inter-layers reduced the number of dislocations. It was also found that a strained inter-layer which had a larger lattice constant than InP did not reduce the dislocation density. The results were explained in terms of the misfit dislocation networks which were believed to form at strained inter-layer interfaces and cause the dislocation reduction effect.

Y.Okuno, T.Kawano: Journal of Crystal Growth, 1994, 145[1-4], 338-44