Molecular beam epitaxial growth of ultrathin buried metal layers: (Al,Ga)As/NiAl/(Al,Ga)As heterostructures

We report the first growth of epitaxial NiAl metallic layers buried within monocrystalline GaAs/AlAs/NiAl/AlAs/GaAs heterostructures deposited entirely within a molecular beam epitaxy growth chamber. The layer growth sequence is monitored by reflection high-energy electron diffraction. Cross-sectional transmission electron microscopy shows that the metal layers and the III-V overgrowth are monocrystalline and of high quality. Thin, buried NiAl layers over the entire thickness range investigated (3–100 nm) are electrically continuous (69 μΩ cm at 3 nm). The heterostructures formed by this process can be used for the fabrication of thin-metal buried-layer devices utilizing ballistic transport or quantum mechanical tunneling across thin metal bases.