The composition dependence of the Fermi-level pinning at the oxidized ͑0001͒ surfaces of n-type In x Ga 1−x N films ͑0 ഛ x ഛ 1͒ is investigated using x-ray photoemission spectroscopy. The surface Fermi-level position varies from high above the conduction band minimum ͑CBM͒ at InN surfaces to significantly below the CBM at GaN surfaces, with the transition from electron accumulation to depletion occurring at approximately x = 0.3. The results are consistent with the composition dependence of the band edges with respect to the charge neutrality level.

Epitaxial scandium nitride films (225nm thick) were grown on silicon by molecular beam epitaxy, using ammonia as a reactive nitrogen source. The main crystallographic orientation of ScN with respect to Si is (111)ScN‖(111)Si and [1–10]ScN‖[0–11]Si; however, some twinning is also present in the films. The films displayed a columnar morphology with rough surfaces, due to low adatom mobility during growth. The strain-free lattice parameter of ScN films grown under optimized conditions was found to be 4.5047±0.0005Å, as determined using high-resolution x-ray diffraction (HRXRD). In-plane and out-of-plane strains were subsequently evaluated using HRXRD and were used to determine the Poisson ratio of ScN along the ⟨111⟩ direction, which is found to be 0.188±0.005. Wafer curvature measurements were made and combined with the strain information to determine the average Young’s modulus of the films, which is found to be 270±25GPa. Residual film stresses ranged from −1to1GPa (depending on film growth temperature and film thickness) due to competition between the tensile stress (induced by the differential thermal contraction between the ScN film and the Si substrate) and intrinsic compressive stresses generated during growth.

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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.