Growth and characterization of gallium nitride on lattice-matched magnesium calcium oxide

As the interest for Gallium Nitride based materials and devices expand, focus on controlling the quality of material is becoming a priority. In this study, the focus of GaN growth upon a lattice tunable oxide is investigated. The oxide utilized is MgCaO. This oxide has the unique feature of maintaining single phase as the metal ratios are varied. Lattice parameter of the oxide is therefore able to be changed and matched to that of GaN. With a matched substrate, the subsequent GaN growth has less strain which results in decreased level of defects in the film, which would normally lead to degraded performance and early device failure. Higher quality material lends itself to further applications. Applications such as nanobar fabrication and oxide etching resulting in GaN film transfer to other substrates.;Another issue encountered in the expansion of GaN devices is heat generation. Heat buildup in high-power RF devices has been the crutch for most material systems. Having the ability to dissipate heat from the device permits greater performance at higher operating loads and longer device lifetime. Therefore, to transfer GaN onto high thermal conductivity substrates would warrant a greater range for device operation, as the heat is more efficiently dissipated through the substrate. The MgCaO substrate can be easily etched away while leaving overgrowth nitride intact, lending itself to the concept of lift-off or pick-and-place. Transfer of GaN onto diamond substrates or other comparable materials would enable the high thermal conductivity and would facilitate the GaN devices to work at higher temperatures and power loads. The substrate transfer could be accomplished after the material growth or after the device fabrication was complete.;In this work, the growth and characterization of single crystal MgCaO epitaxial films have been demonstrated. This has been demonstrated on single crystal GaN epifilms grown on sapphire, but SiC can be employed as well, eliminating the underlying GaN epifilm. Oxide thicknesses over 100nm with surface RMS roughness of less than 0.5nm have been achieved and employed as a successful substrate for nitride based overgrowth.