Nitrogen- and ammonia-plasma nitridation of hydrogenated amorphous silicon

Nitrogen- or ammonia-plasma nitridation of hydrogenated amorphous silicon (a-Si:H) was carried out. A nearly stoichiometric silicon nitride layer with a thickness of several tens Å is formed on a-Si:H. The nitride-layer thickness linearly increases with an increase in the nitridation time after a rapid increase in the early stage. The neutral-Si-dangling-bond (DB) density in the a-Si:H layer rapidly increases in the early stage of the nitridation, then it gradually decreases as the nitridation time increases. The larger increase in the neutral-Si-DB density in the early stage of the nitridation is observed in the nitrogen-plasma nitridation or at lower nitridation temperature. On the other hand, the sum of neutral- and charged-Si-DB densities in a-Si:H layer does not decrease with an increase in the nitridation time as the neutral-DB density does, suggesting that the charge injection from the nitride layer to the a-Si:H layer originating from the band bending occurs with the formation of the nitride layer on a-Si:H.