CATHODOLUMINESCENCE FROM RELAXED GEXSI1-X GROWN BY HETEROEPITAXIAL LATERAL OVERGROWTH

We present low temperature cathodoluminescence (CL) studies of relaxed GexSi1-x, selectively grown on a patterned Si (111) substrate by liqu id phase epitaxy, using heteroepitaxial lateral overgrowth. In the spe ctrally resolved CL of the resulting GeSi crystals, we observe an emis sion peak attributed to the recombination of free excitons (FEs). We f urther observe a peak of lower intensity at a lower energy position, c aused by the unresolved phonon replicas of the FE peak. At an even low er energy position, we observe a comparatively broad luminescence band , attributed to CL from dislocations. Monochromatic images using the F E emission, or its phonon replica, reveal three types of contrast vari ations. On a 5 mum scale we observe dark line defects in the GeSi crys tals, which we attribute to dislocations. In the lateral position of t he seeding windows for the epitaxy, the GeSi crystals exhibit a dark, 20 mum wide band. On a 20 to 50 mum scale we observe small fluctuation s in the GexSi1-x composition, which manifests itself as local intensi ty variations with detection wavelength.