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

Trapping levels which govern the vertical transport in (nc-Si/CaF2)(n) mult i-quantum wells were investigated using two different techniques: (a) the t emperature dependence of the dark current and (b) the thermally stimulated depolarization current technique (TSDC). Measurements by the first techniqu e showed that the conduction mechanism was thermally activated above 200 K with activation energies of 0.35-0.7 eV, These activation energies were fou nd to increase with increasing electric field. TSDC measurements showed als o the existence of at least one broad peak above 200 K with estimated activ ation energies in the range of 0.4-0.45 eV. Analysis of the peak by the fra ctional heating method showed a continuous distribution of defect states fr om 0.3 to 0.83 eV. (C) 2001 Elsevier Science B.V. All rights reserved.