GROWTH-MORPHOLOGY EVOLUTION AND DISLOCATION INTRODUCTION IN THE INGAAS GAAS HETEROEPITAXIAL SYSTEM/

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