ON THE CORRELATION AMONG PHOTODEGRADATION, CHARGED DANGLING BONDS AND MICROSTRUCTURE IN HYDROGENATED AMORPHOUS-SILICON

We propose that in hydrogenated amorphous silicon the mechanism of conversion from charged to neutral dangling bonds adds to the weak Si-Si bond breaking during light soaking. Our model is developed from an equilibrium picture of the density of states as given by the defect pool theory [K. Winer, Phys. Rev. B 41, 150 (1990)] and predicts an increase rate of the neutral dangling bonds density (D-0) proportional to (1/D-0)(2), which is related either to the charged defect conversion probability and to the bond-breaking probability. This model explains photoconductivity experiments and, in particular, the short-time features: it shows that the photodegradation is enhanced in clustered hydrogen-rich samples provided the density of charged dangling bonds is correlated with the clustered hydrogen present in the amorphous network.