Structure or device comprises a AlxGa1-xN or InyGa1-yN layer or substrate, a rare earth nitride epitaxial layer, and an AlzGa1-zN epitaxial interlayer between the rare earth nitride epitaxial layer and the AlxGa1-xN or InyGa1-yN layer or substrate. The interlayer is in direct contact with the rare earth nitride epitaxial layer and the AlxGa1-xN or InyGa1-yN layer or substrate.