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 depend ence of the minority-carrier concentration. The model simulation analyses o f the temperature dependence of gamma (h) and the phototransport properties of the majority carriers show that these unprecedented low values in gener al, and in a-Si:H in particular, are associated with the presence of an acc eptorlike center, the energy level of which lies 0.3-0.5 eV above the valen ce-band edge. Our results show then that the common analyses of the photoel ectronic 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 propos ed to exist in a-Si:H can be identified now as oxygen-induced acceptorlike centers.