Control of threading dislocations by strain engineering in GaInP buffers grown on GaAs substrates

High quality strain-relaxed In0.3Ga0.7As layers with threading dislocation density about 2×106cm−2 and root-mean-square surface roughness below 8.0nm were obtained on GaAs substrates using compositionally undulating step-graded Ga1−xInxP (x=0.48–0.78) buffers. The transmission electron microscopy results reveal that the conventional step-graded GaInP buffers produce high density dislocation pile-ups, which are induced by the blocking effect of the nonuniform misfit dislocation strain field and crosshatched surface on the gliding of threading dislocations. In contrast, due to strain compensation, insertion of the tensile GaInP layers decreases the surface roughness and promotes dislocation annihilation in the interfaces, and eventually reduces the threading dislocation density. This provides a promising way to achieve a virtual substrate with the desired lattice parameter for metamorphic device applications.