A possible mechanism for improved light-induced degradation in deuterated amorphous-silicon alloy

We have studied light-induced photoconductivity degradation in an intrinsic hydrogenated and deuterated amorphous-silicon (a-Si) alloy. Deuterated a-Si turns out to be more stable under light exposure. A possible mechanism is proposed to explain this phenomenon. It is attributed to the highly efficient coupling between the localized Si-D wagging modes (similar to 510 cm(-1)) and the extended Si-Si lattice vibration modes (similar to 495 cm(-1)). The energy released from electron or hole capture at silicon dangling bonds causes localized vibrations of nearby Si-D bonds. The energy dissipates quickly to the background lattice and a higher recombination rate at local sites is needed in deuterated a-Si than in hydrogenated amorphous silicon to accumulate enough energy to break the nearby weak bonds. (C) 1997 American Institute of Physics.