Characterization of planar growth defects in slightly-mismatched InGaAs/InP heterostructures

InxGa1-xAs/InP heterostructures (with x ∽ 0.56) have been grown by low pressure MOCVD and characterized by cross-sectional TEM. When the interfaces are inclined with respect to the electron beam, they are imaged with a complex (α + δ)-fringe contrast. This contrast is interpreted as resulting from significant variations of the As and Ga contents in the InGaAs layer near the interfaces. Fringes with a weaker contrast are also observed in the ternary layers; they are parallel to the (001) interface plane and they show the same characteristics as the preceding fringes. They are considered as arising from (001) planar growth defects which correspond to step-graded variations of composition in ternary layers. This interpretation is corroborated by the results of X-ray double crystal diffraction experiments.