Switching of deep levels in CuInSe2 due to electric field-induced Cu ion migration

To search for the origin of the 0.26 eV deep hole trap, which is well established in p-type CuInSe2 single crystals and thin films, we investigated the influence of electric field-induced Cu ion migration on this level. We show that this hole trap can be removed from the space charge region of a reverse-biased Schottky barrier in p-type CuInSe2 single crystals by annealing at 490 K for 10 min. Simultaneously, a new hole trap at 0.49 eV from the valence band is created in this region. Conversely, the application of a forward bias under the same annealing conditions causes a decrease in the concentration of the 0.49 eV hole trap and a recreation of the 0.26 eV hole trap to the original state. These two processes were found to be reversible. Our results are completely consistent with recent evidence of an electric field-induced Cu ion migration via a vacancy mechanism in CuInSe2. According to a recent theoretical paper on the defect physics of CuInSe2, a candidate for experimentally observed 0.26 eV deep hole trap seems to be the simple acceptor Cu-In(-/0). (C) 1998 American Institute of Physics. [S0021-8979(98)08720-9].