Interface formation between an ultra thin MgO layer and the selenium passivated InAs surface has been investigated by soft X-ray photoemission spectroscopy. Atomic hydrogen cleaning of the native oxide covered InAs at 360 C produced an oxide and carbon free InAs surface. The selenium passivation of the atomically clean InAs showed evidence of arsenic replacement in the near surface region. Subsequent MgO deposition resulted in the appearance of an oxidized indium signal indicating that the bonding interaction between the MgO and the substrate is via indium-oxide bond formation. The conduction and valence band offsets were also estimated for this dielectric-semiconductor structure. © 2013 Elsevier B.V. All rights reserved.