Interfacing Cubic Gallium Nitride with other Cubic Nitrides to Unlock Exotic Materials Properties

Group III-nitride materials such as GaN have become an integral part of the optoelectronics industry. GaN traditionally adopts a wurtzite structure (h-GaN), but it also has a metastable zinc blende allotrope (c-GaN). One of the potential advantages of this allotrope is its ability to interface much easier with the other transition metal nitrides, which are also cubic. If the growth of c-GaN could be stabilized epitaxial integration with these materials would open a world of new possibilities in band engineering, as well as the ability to create new device structures for areas such as nuclear fuels, quantum computing, and condensed matter physics.

We report successful synthesis of c-GaN, and its integration with known superconductor ZrN, via molecular beam epitaxy. The team stabilized c-GaN by carefully controlling the ratio of Ga and N atoms impinging on the substrate surface. The cubic structure of the c-GaN films was confirmed via in-situ RHEED and ex-situ XRD and photoluminescence. Our results suggest an atomic flux ratio closer to 1:1 helps to suppress the hexagonal phase. Superlattices of c-GaN/ZrN were also successfully deposited very recently. The structure of these films was confirmed via RHEED and XRD, and the interface quality is being investigated via TEM.

These results are informing future depositions, where the layer thicknesses will be carefully tuned to enhance superconductivity within ZrN. Integration of c-GaN with other nitrides such as Cr-, Mn-, and NiN is also planned.