The time evolution of the 1.54 mu m Er3+ photoluminescence intensity of Er-doped silicon following a 30 mu s excitation pulse is investigated. It is found that at 9 K, the 1.54 mu m luminescence from Er3+ continues to increase up to 50 mu s after the pulse is terminated, when excess photocarriers no longer exist. This provides the first direct experimental evidence that a state in the forbidden gap of silicon acts as the gateway to the excitation of Er3+. Further analysis indicates recombination of bound excitons to be the most likely excitation mechanism. (C) 1995 American Institute of Physics.