Effect of buffer layer structure on the structural properties of GaAs epitaxial layers grown on GaP substrates

Three-mu m-thick GaAs layers were grown on 2 degrees-off (1 0 0) GaP substrates by employing various buffer layer structures, which consist of GaAsP- and InGaAs-based ternary compound semiconductors. To confirm the effects, we altered the layer thickness, the interface lattice mismatch, and number of the layers in the buffer layer structure, and also a superlattice structure was employed in some of the buffer layers. The lattice constants of the layers were controlled by changing the As/P and In/Ga compound ratios. The crystal properties of the grown GaAs layers were characterized with X-ray diffraction, photoluminescence, and etch pit density observations. The effect of the buffer layer structure on the crystallographic character of the GaAs layers was analyzed by introducing a parameter that is a function of the thickness and interface lattice mismatch of each layer in the buffer layer structure. The results suggest that the GaAs layer is relatively relaxed but contains a greater number of dislocations for smaller layer thicknesses and greater lattice mismatches in the buffer layer structure, while the GaAs layer has a smaller number of dislocations but a rather deformed lattice structure for larger layer thicknesses and smaller lattice mismatches. Our parameter is useful for developing design principles of buffer layer structures.