ATOMIC-SCALE MORPHOLOGY AND INTERFACES OF EPITAXIALLY EMBEDDED METAL (COAL)/SEMICONDUCTOR (GAAS/ALAS) HETEROSTRUCTURES

We have grown GaAs/AlAs/CoAl/AlAs/GaAs epitaxially embedded metal/semiconductor heterostructures by molecular beam epitaxy. When the growth temperature of overgrown GaAs is relatively low (440-degrees-C), the buried metallic CoAl film with the thickness of 50 angstrom is uniform and planar with extremely smooth and abrupt metal/semiconductor interfaces. The top (AlAs-on-CoAl) interface is atomically smooth with the roughness of at most 1 monolayer, while the bottom (CoAl-on-AlAs) interface has the roughness of 2-3 monolayers. This sample shows very low resistivity of 11-41-mu OMEGA cm at room temperature, indicating that the electrically continuous metallic film is grown. In contrast, when the GaAs overlayer is grown at 580-degrees-C, CoAl dots with the size of 200-250 angstrom, which are covered with {001} and {111} facets, are fabricated, resulting from agglomeration.