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 (∼510 cm−1) and the extended Si–Si lattice vibration modes (∼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.