Picosecond luminescence and competing nonradiative processes in As2S3 glass

Photoluminescence (PL) in As2S3 glass was measured with 7-psec resolution using a streak camera. We find that the Stokes shift occurs in <20 psec, and that the maximum radiative rate is 1=(4±1)×108 Hz. Nonradiative decay dominates at high T, but persists at low T, probably due to tunneling. For T>100 K the observed decay time varies as exp(-TT0) like the cw PL efficiency, indicating that similar nonradiative mechanisms may apply for slow and fast PL. We suggest that transient absorption and PL probe different carrier subsets. A localized exciton model is discussed in relation to the fastest PL processes.