CHARGED DEFECT STATES IN INTRINSIC HYDROGENATED AMORPHOUS-SILICON FILMS

Steady-state photoconductivity, sub-band-gap absorption and electron s pin resonance (ESR) measurements were carried out on annealed and ligh t soaked intrinsic hydrogenated amorphous silicon (a-Si:H) films. The experimental results were modeled using detailed numerical analysis. T he defect densities derived from the sub-band-gap absorption in the li ght soaked films were correlated with the ESR spin densities. Self-con sistent fitting of the data was obtained using a gap state distributio n which consists of positively charged defect states above, negatively charged defect states below and neutral defect states at about the mi dgap. Both the annealed and the light degraded states are modeled usin g the same gap states which increase upon light soaking and have a sli ght increase in the ratio of the neutral to charged defect densities. These results on intrinsic a-Si:H are consistent with proposed charged defect models and clearly indicate the importance of charged defect s tates in determining sub-band-gap absorption as well as its correlatio n with neutral dangling bonds.