the authors report on the fabrication of a composite gaas-sio/sub 2/ nucleation layer. the layer is formed by a deposition of a gaas island layer by molecular beam epitaxy (mbe), followed by an oxidation step of the silicon regions surrounding the islands. in this way, small gaas islands, for which the critical thickness for misfit dislocation generation is increased, are surrounded by a stable amorphous phase. lateral overgrowth seeded by the individual gaas islands might enhance the overall epilayer quality. the authors describe the fabrication and cleaning of such a composite gaas-sio/sub x/ nucleation layer that is compatible with the epitaxy process. preliminary regrowth on a non-optimized composite surface resulted in gaas-on-silicon quality equal to standard gaas-on-silicon. compared with gaas epitaxy on porous silicon, another seeded growth technique, the composite surface technique has greater technological potential for the monolithic integration of gaas and silicon electronics