Molecular Beam Epitaxy of Transition Metal Nitrides for Superconducting Device Applications

Integration of epitaxial superconducting layers with semiconductor devices is expected to enable substantial performance benefits, design flexibility, and creation of novel device structures. Integration of superconducting transition metal nitrides (TMNs) with the wide bandgap group III-N semiconductors is especially appealing because of the close lattice match, similar crystal structures, and chemical and thermal compatibility of the TMN and III-N families of materials. We have previously reported on the use of a Scienta-Omicron PRO-75 RF-plasma molecular beam epitaxy (MBE) chamber equipped with an in-situ electron beam evaporator to epitaxially grow metallic niobium nitride (NbN
x
) thin films and III-N/NbNx heterostructures on hexagonal SiC substrates. More recently, we have reported on growth of single-phase thin films of single-crystal hexagonal
$\gamma$
-Ta
2
N on 3-inch-diameter SiC substrates. In this presentation, we will discuss our recent work on the growth and superconducting properties of TMNs grown on SiC by MBE. The films were characterized in-situ using reflection high-energy electron diffraction, and ex-situ using optical and atomic-force microscopy, contactless sheet resistance, X-ray diffraction, cross-sectional transmission electron microscopy, and superconductivity measurements. We will discuss the MBE growth conditions for epitaxial superconducting NbNx and hexagonal
$\gamma$
-Ta
2
N on SiC.