Preferential growth mode of cubic GaN by metalorganic molecular beam epitaxy on sapphire (0001) substrates

Growth of GaN on sapphire (0001) substrates by metalorganic molecular beam epitaxy (MOMBE) was studied using triethyl gallium (TEGa) and rf-plasma excited active nitrogen. A series of samples were grown under various TEGa flow rates while growth temperature (800 degrees C) and nitrogen supply were fixed. At a very low TEGa flow rare, the grown layer was polycrystalline. With increasing TEGa now rate, the dominant polytype of the grown layer changed from hexagonal GaN (h-GaN) to cubic GaN (c-GaN). From the dependence of growth rate on TEGa flow rates, it was revealed that a Ga-stabilized growth condition results in the growth of c-GaN. By increasing growth time, the c-GaN composition became larger, indicating preferential growth of c-GaN.