Electrical conductivity of amorphous silicon doped with rare-earth elements

This work reports on the electrical properties of a-Si samples doped with elements of the lanthanide series. A detailed study of gadolinium-doped a-Si is presented. It has been found that the introduction of rare-earth elements into the amorphous-silicon network produces large changes in the conductivity. An analysis of the experimental conductivity as a function of temperature and rare-earth content, together with the optical and electron-spin-resonance data, leads us to suggest that rare-earth-acceptor-like states located in the lower half of the pseudogap may be responsible for the measured properties.