Structural characterization of ingaas/inp heterostructures grown under compressive and tensile stress

A systematic study of strain relaxation mechanisms by TEM, XRD, RBS-channelling, SEM-CL and AFM in InxGa1-xAs/InP heterostructures grown by MOCVD under tensile and compressive initial misfit is reported. It is found that the layers under compression (0.61<x<0.74) relax nearly symmetrically along the two <110> directions. The residual strain vs. the layer thickness follows the same law experimentally determined for compressive MBE-grown InxGa1-xAs/GaAs(x<0.2) specimens showing no composition, growth technique or temperature effect. The tensile layers (0.2<x<0.36) relax asymmetrically with a critical thickness larger than for the compressive case. The relaxation is faster along the [110]-direction with the asymmetry that increases by increasing the tensile misfit. Cracks, formed after the growth, are found to present a different density along [110] and [1-10] depending on the residual strain. Grooves also develop along the two <110> directions as soon as a measurable strain relaxation appears. A possible correlation between grooves, planar defects and the mechanism of strain release is discussed.