Valence band edge tail states and band gap defect levels of GaN bulk and InxGa1-xN films detected by hard X-ray photoemission and photothermal deflection spectroscopy

Tail states near the valence band maximum (VBM) and in-gap states of GaN bulk and InxGa1-xN films are observed by hard X-ray photoemission spectroscopy, and the fine structures of these defect states are characterized by photothermal deflection spectroscopy. The defects are enhanced with increasing InN mole fraction, indicating that they originate in cation-related defects and their complexes. The structural disorder, defined as the inverse of the slope of the VBM, becomes larger. Taking the semiconductor properties into account, we consider that the tail state defects are strongly localized, which implies that a mobility edge may exist for GaN and InxGa1-xN. (c) 2018 The Japan Society of Applied Physics