Direct verification of energy back transfer from Yb 4f-shell to InP host

We report direct verification of energy back transfer from a Yb 4f-shell to an InP host, which has been proposed as a quenching mechanism for the intrinsic thermal quenching of intra-4f-shell luminescence. Photoluminescence time decay of the band-edge related luminescence for a Yb-doped InP sample was examined. In the temperature region from 100 to 120 K, it was observed that the luminescence time-decay curve is composed of two exponential decay components. The decay-time constant of the slower component in the band-edge related luminescence is the same as that in the Yb 4f-shell luminescence. This fact clearly shows that there is an energy transfer between the Yb 4f-shell electronic state and the InP host electronic state, and the energy back-transfer mechanism is the cause of the intrinsic thermal quenching of the Yb intra-4f-shell luminescence.