Abstract
A strong electron accumulation was observed in near-surface regions of undoped and Mg-doped In-polar InN films by analyzing the valence band maximum dependent on the take-off angles. The amount of oxygen correlated with electron carrier concentration drastically increased in both near-surface regions, suggesting that the oxygen atoms in both near-surface regions act as donors. For Mg-doped InN, the amount of oxygen in the near-surface region was almost twice that of undoped InN, indicating that much more oxygen atoms in the near-surface region were incorporated to compensate the Mg acceptors to contribute to the electron accumulation surface layer.