PHOTOCONDUCTIVE PROPERTIES OF HYDROGENATED AMORPHOUS-SILICON IN THE LIGHT OF THE POSITIVE DANGLING BOND AS THE MAIN RECOMBINATION CENTER - CONSEQUENCES FROM THE DEFECT POOL MODEL

We discuss the photoconductive properties of hydrogenated amorphous si licon in the presence of comparable numbers of neutral and charged dan gling bond defects and in particular for the defect distribution accor ding to the defect pool model. We numerically model transient and modu lated photoconductivity experiments. Analysis of time-of-flight data i dentifies the deep-trapping time with the capture time into the positi ve dangling bond. Testing numerically the equivalence of secondary tra nsient and modulated photoconductivity employed for spectroscopic purp oses, we reproduce the experimental optical bias effect in the modulat ed photocurrent spectra and the related change in the reconstructed de nsity of states. We suggest performing these spectroscopic experiments with a series of slightly p-type doped samples for which the numerica l modelling reveals two differently shaped reconstructed density of st ate profiles for either the defect pool or a single defect band distri bution. (C) 1998 Elsevier Science B.V. All rights reserved.