Improved quality of In0.30Ga0.70As layers grown on GaAs substrates using undulating step-graded GaInP buffers

High quality In0.30Ga0.70As layers on GaAs substrates were obtained using compositional undulating step-graded Ga1-xInxP (x = 0.48-0.78) buffers grown by metal-organic chemical vapor deposition. The density of threading dislocation is about 4.0 × 106 cm−2 and the root-mean-square roughness is only 5.20 nm, which is much better than those grown on the conventional step-graded metamorphic buffer. On one hand, the reversed GaInP layers reduce the distribution imbalance of α dislocations between the (1 1 1) and (−1 −1 1) slip planes, which promote dislocation glide. On the other hand, the inserted tensile strained GaInP layers change the direction of dislocation glide and facilitate dislocation annihilations, which effectively confine the threading dislocations in the buffer. Overall, this work provides a promising way to obtain virtual substrates for the achievement of desired metamorphic devices.