Growth morphology evolution and dislocation introduction in the InGaAs/GaAs heteroepitaxial system

The present work examines in detail heteroepitaxial InxGa1-xAs alloy layers on GaAs by use of complementary transmission electron microscopy and atomic force microscopy. The characteristics of the low In x-value, smooth growth regime are established in terms of surface step configurations. Progressively increasing irregularities in step fronts and monolayer island formation with increasing In concentration in the alloy are linked with the transition to undulating growth as an x-value of 0.25 is approached. The evolution of high x-value roughened layers is studied and the structure changes with increasing film thickness and In content are determined. The manner in which final ripple arrays evolve from isolated islands is described and the stress interaction between islands is highlighted. The magnitude of the periodic elastic stress field which accompanies the formation of the ripple structures is microscopically measured and is shown to yield essentially complete misfit relief within the ripple crests. The increased stress present at ripple troughs is shown to lead to misfit defect source behaviour, which is expected to be of wide-ranging importance for defect generation in strained, undulating epitaxial films in general.