Spectral response of Schottky diodes on hydrogenated amorphous silicon: Effects of gap states

The spectral response of Schottky diodes on hydrogenated amorphous silicon has been determined between 1 and 3.5 eV. An anomalous absorption peak clearly appears at low energy from these experiments. We have demonstrated that this peak is due to optical transitions from localized states near the valence band to the conduction band, and is connected with hole trapping during the transport.