Influence of GaAs substrate misorientation on the characteristics in undulating compositional step-graded AlGaInAs buffers

Undulating compositional step-graded AlGaInAs buffers are applied to transit the lattice mismatch of 3.8% between InP cap layer and GaAs substrates with misorientation of 2°, 7° and 15° toward (111)A by metal organic chemical vapor deposition (MOCVD). The surface morphology and strain relaxation are strongly dependent on the substrate misorientation. The sample grown on 15° GaAs substrate showed a substantial improvement of surface roughness and reduction of dislocation pile-up densities compared with that on the 2° and 7° substrate. The experiment results showed that the substrate with 15° misorientation can maintain a smooth epitaxial film surface by increasing the possibility of atoms incorporating into the lattice and ease the imbalance of the misfit strain stress distributed between different slip systems to make dislocations distributed more uniformly, which can reduce the strain field to exaggerate the channel width for dislocation gliding along the interface and decrease the threading dislocation densities. Overall, this work provides a promising way to obtain virtual substrates for the achievement of desired metamorphic devices.