The origin of visible photoluminescence in low power a-Si1-xCx : H with x > 0.2

Photoluminescence decay measurements were performed in a series of a-Si1-xC x:H samples with 0 < x < 0.5 prepared in the low power regime, i.e. contain ing virtually no sp(2) carbon. The decay is non-exponential and presents tw o peaks in the lifetime distribution for x > 0.2, one slow peak associated to a-Si:H-like luminescence and a fast peak that is responsible for the tem perature independent visible luminescence. We conclude that the efficient t emperature independent visible photoluminescence is due to a mechanism that is ineffective in a-Si:H, which we attribute to enhanced Coulomb interacti on between electron and hole. (C) 1999 Elsevier Science Ltd. All rights res erved.