Solid-state devices including a layer of a superconductor material epitaxially grown on a crystalline high thermal conductivity substrate, the superconductor material being one of TiNx, ZrNx, HfNx, VNx, NbNx, TaNx, MoNx, WNx, or alloys thereof, and one or more layers of a semiconducting or insulating or metallic material epitaxially grown on the layer of superconductor material, the semiconducting or insulating material being one of a Group III N material or alloys thereof or a Group 4b N material or SiC or ScN or alloys thereof.