The present invention provides materials, structures, and methods for III-nitride-based devices, including epitaxial and non-epitaxial structures useful for III-nitride devices including light emitting devices, laser diodes, transistors, detectors, sensors, and the like. In some embodiments, the present invention provides metallo-semiconductor and/or metallo-dielectric devices, structures, materials and methods of forming metallo-semiconductor and/or metallo-dielectric material structures for use in semiconductor devices, and more particularly for use in III-nitride based semiconductor devices. In some embodiments, the present invention includes materials, structures, and methods for improving the crystal quality of epitaxial materials grown on non-native substrates. In some embodiments, the present invention provides materials, structures, devices, and methods for acoustic wave devices and technology, including epitaxial and non-epitaxial piezoelectric materials and structures useful for acoustic wave devices. In some embodiments, the present invention provides metal-base transistor devices, structures, materials and methods of forming metal-base transistor material structures for use in semiconductor devices.