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UV Photoemission Study of AlGaN Grown by Metalorganic Vapor Phase Epitaxy

The electronic surface properties of AlxGa1-xN have been studied with ultraviolet photoemission spectroscopy (UPS). Samples were grown by metalorganic vapor phase epitaxy and prepared with multiple cycles of nitrogen ion sputtering and annealing to obtain clean surfaces. The energy position of the valence band maxima of the GaN surface was at 3.0 eV below the Fermi level and the upward band bending was 0.35 eV. The widths of the UPS energy distribution curves of AlxGa1-xN yielded the ionization energy, and the electron affinity was determined to be 3.6–2.9 eV for x = 0–0.6. It was found that the electron affinity of AlxGa1-xN was positive and reduced with increasing the AlN molar fraction.