Trapping levels in (nc-Si/CaF2)n multi-quantum wells

Trapping levels which govern the vertical transport in (nc-Si/CaF2)n multi-quantum wells were investigated using two different techniques: (a) the temperature dependence of the dark current and (b) the thermally stimulated depolarization current technique (TSDC). Measurements by the first technique showed that the conduction mechanism was thermally activated above 200 K with activation energies of 0.35–0.7 eV. These activation energies were found to increase with increasing electric field. TSDC measurements showed also the existence of at least one broad peak above 200 K with estimated activation energies in the range of 0.4–0.45 eV. Analysis of the peak by the fractional heating method showed a continuous distribution of defect states from 0.3 to 0.83 eV.