The origin of visible photoluminescence in low power a-Si 1− xC x:H with x>0.2

Abstract

Photoluminescence decay measurements were performed in a series of a-Si 1− x C x :H samples with 0< x<0.5 prepared in the low power regime, i.e. containing virtually no sp 2 carbon. The decay is non-exponential and presents two 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 temperature independent visible luminescence. We conclude that the efficient temperature independent visible photoluminescence is due to a mechanism that is ineffective in a-Si:H, which we attribute to enhanced Coulomb interaction between electron and hole.