Sensitization of the electron lifetime in a-Si:H:: The story of oxygen -: art. no. 113201

We have found, in hydrogenated-amorphous silicon (a-Si:H), values as low as 0 for the exponent gamma (h) that characterizes the light-intensity dependence of the minority-carrier concentration. The model simulation analyses of the temperature dependence of gamma (h) and the phototransport properties of the majority carriers show that these unprecedented low values in general, and in a-Si:H in particular, are associated with the presence of an acceptorlike center, the energy level of which lies 0.3-0.5 eV above the valence-band edge. Our results show then that the common analyses of the photoelectronic properties of a-Si:H only in terms of dangling bonds and band-tail states are not justified, and that the "safe hole traps'' that were proposed to exist in a-Si:H can be identified now as oxygen-induced acceptorlike centers.