Structural properties of wurtzitelike ScGaN films grown by NH3-molecular beam epitaxy

Scandium gallium nitride (ScxGa1-xN) alloy films with low Sc concentrations (up to approximately x=0.08) were grown using molecular beam epitaxy with NH3 as a reactive N source, on GaN films that were grown on sapphire using metalorganic vapor phase epitaxy (MOVPE). High-resolution x-ray diffraction and transmission electron microscopy revealed that both the c and the a lattice parameters increased with increasing Sc concentration, as predicted for a wurtzite-structure alloy. As the Sc content increased, the relaxation of the compressive stress in the ScxGa1-xN films occurred mainly via the introduction of additional a-type dislocations, but neither stacking faults nor significant compositional segregation was observed at any composition. A dewetting effect (which increased with increasing Sc content) was observed in MOVPE-grown GaN deposited on top of the ScxGa1-xN films, but the ScxGa1-xN remained compositionally and structurally stable under GaN growth conditions.