Determination of the branch-point energy of InN: Chemical trends in common-cation and common-anion semiconductors

Bulk and surface electronic properties of Si-doped InN are investigated using high-resolution x-ray photoemission spectroscopy, optical absorption spectroscopy, and quasiparticle corrected density functional theory calculations. The branch point energy in InN is experimentally determined to lie 1.83 +/- 0.10 eV above the valence-band maximum. This high position relative to the band edges is used to explain the extreme fundamental electronic properties of the material. Far from being anomalous, these properties are reconciled within chemical trends of common-cation and common-anion semiconductors.