Interfacial Microstructure of InxGa1-xAs/GaAs Strained Layers

The topography and defect structure of interfaces in InGaAs/GaAs strained-layer structures grown by molecular beam epitaxy were investigated by transmission electron microscopy. A large range of indium fractions, x, was investigated: 0.16 ≥ x ≥ 1.00, and three different critical layer thicknesses, corresponding to the formation of three different types of defects, were observed with increasing thicknesses of the strained layers. These defects were: rough interfacial topographies resulting from an onset of 3-dimensional growth for the InGaAs layers; misfit dislocations of the 60° mixed type; and dislocation complexes consisting of planar defects on {111} planes. Compared with results obtained from photoluminescence measurements it was found that both types of defects involving dislocations resulted in severe degradation of the optical properties of the strained-layer structures.