It was recalled that persistent photoconductivity was an enhanced dark conductivity that was observed, after illumination, in the doping superlattices of amorphous hydrogenated Si. Similarities in the creation and annealing of persistent photoconductivity, and the Staebler-Wronski effect (creation of metastable defects under illumination) had led to the proposal of a model in which persistent photoconductivity was linked to defect creation in the p-layers of the superlattice. The model was tested here by simultaneously measuring the persistent photoconductivity and defect density of an npnp-doping superlattice. A marked temperature dependence of the build-up of persistent photoconductivity was found, whereas the number of defects that was created within a given illumination time was independent of the temperature at which light-soaking was performed. It was concluded that the Staebler-Wronski effect was not responsible for the persistent photoconductivity of doping superlattices. Instead, special defect centers with an electronic barrier to hole trapping and excitation were thought to be responsible for persistent photoconductivity.

G.Weigelt, M.Hundhausen, L.Ley: Solid State Phenomena, 1995, 44-46, 495-504