Light-induced degradation of an intrinsic hydrogenated amorphous sample was monitored via the evolution of the sub-bandgap absorption coefficient. The results were analyzed by using detailed numerical analysis, and this yielded the defect distribution within the gap for each illumination time. It was found, in agreement with previous work, that the defect density indicated the presence of more charged, than neutral, defects; as predicted by the defect-pool model. The concentrations of the charged and neutral defects evolved with the same time-dependence, thus contradicting the generalized Schumm model for defect equilibration.

Light-induced creation of metastable defects in hydrogenated amorphous silicon J.A.Schmidt, R.D.Arce, R.R.Koropecki, R.H.Buitrago: Physical Review B, 1999, 59[7], 4568-71