The barrier height of a metal-semiconductor contact was studied by means of angle-resolved photoemission spectroscopy, which was implemented through stepwise Ag deposition on the ultra-high vacuum cleaved (111) surface of melt-grown In2O3 single crystals. A small Schottky barrier height of 0.22 ± 0.08 eV was determined by following the band bending of the valence band and core level spectra with Ag thickness and corrected for the photovoltage effect. In addition, the work function of Ag and the electron affinity of In2O3 were measured in situ to be 4.30 ± 0.05 eV and 4.18 ± 0.06 eV, respectively. Agreement was observed when comparing the barrier height from band bending to the calculated one by applying the Schottky-Mott rule, yielding a value of 0.12 ± 0.11 eV. Due to an additionally appearing photovoltage, an explicit reference to the surface electron accumulation layer is not necessary when discussing the Schottky character of the Ag/In2O3 contact.

The near-EF band of the in situ cleaved (111) surface of high-quality n-type In2O3 single crystals was investigated by high-resolution angle-resolved photoemission (ARPES) along the major symmetry lines of the three-dimensional Brillouin zone. Several criteria to pin down Fermi level crossings and Fermi momenta were applied. The near-EF band is of three-dimensional character connected to the bottom of the conduction band. Since the model of a degenerate semiconductor due to high n-type doping is not sufficient the interaction of electron and phonon degrees of freedom is discussed. It is found that the model of Landau-Pekar polarons is capable of describing the observed lineshape qualitatively and the bandwidth of the occupied part of the conduction band quantitatively.

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