Evidence for inhomogeneous growth rates in partially relaxed InGaAs/InP heterostructures

The surface morphology and the dislocation structure of thin and thick strained InxGa1−xAs heterostructures grown on (001) InP substrates have been investigated using atomic force microscopy and transmission electron microscopy. Long linear ridges, correlated to underlying dislocations, are detected in thin partially relaxed In0.82Ga0.18As layers. The ridges (with increased height along the [110] direction comparing to along the [1-10] direction) are associated with strong inhomogeneous local growth rates induced by elastic strain relief and controlled by kinetic factors. The crosshatched surface morphology in thick In0.65Ga0.35As layers is explained using the same mechanism with multiplication and interaction of dislocations and ridges during growth. In contrast, the development of isolated ‘‘V-shaped’’ grooves parallel to [1-10] in lattice-matched capping layers grown on partially relaxed In0.82Ga0.18As quantum wells is explained by the generation of surface corrugations in tensile strained regions appearing just above the elongated relaxed region of In0.82Ga0.18As.