Atomic-scale morphology and interfaces of epitaxially embedded metal (CoAl)/semiconductor (GaAs/AlAs) heterostructures

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Abstract
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 °C), the buried metallic CoAl film with the thickness of 50 Å 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 μ Ω cm at room temperature, indicating that the electrically continuous metallic film is grown. In contrast, when the GaAs overlayer is grown at 580 °C, CoAl dots with the size of 200–250 Å, which are covered with {001} and {111} facets, are fabricated, resulting from agglomeration.