Electron affinity at aluminum nitride surfaces

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Abstract
We investigate the electron affinity of aluminum nitride surfaces prepared by nitrogen sputtering and annealing via x-ray, ultraviolet, and inverse photoemission spectroscopy. The combination of these techniques leads to a precise determination of the relative positions of the Fermi level, valence-band maximum, conduction-band minimum, and vacuum level at the semiconductor surface. We demonstrate that, in spite of the presence of a sharp photoemission onset feature previously associated with negative electron affinity, the electron affinity is clearly positive on these surfaces.