Light-induced relaxation of the metastable conductivity of undoped $a$-Si:H films illuminated at elevated temperatures

The kinetics of relaxation of the light-induced (at a temperature above 140$^\circ$C) dark conductivity of undoped $a$-Si:H films is studied. The calculated time dependences of the relaxation rate of the dark conductivity are analyzed under the assumption that the thermal rates of the generation and relaxation of metastable defects formed by preliminary illumination are independent of illumination. It is shown that the features of the kinetics of the relaxation rates of dark conductivity under illumination are determined by the presence of light-induced processes of the relaxation and generation of slowly relaxing metastable defects whose energy levels are located in the upper half of the band gap.