Negative thermal quenching of photoluminescence in ZnO

We have studied photoluminescence (PL) spectra of ZnO single crystals at photon energies ranging between 2.1 and 3.4eV as a function of temperature to determine thermal quenching behavior in PL emission intensity. It appears that the deep level emissions, donor-acceptor pair emissions, and the bound excitonic emissions undergo negative thermal quenching (NTQ) at intermediate temperatures above similar to 10K. By employing an NTQ formula expressed analytically as a function of temperature, we have obtained quantitative NTQ characteristics in terms of the activation energies associated with the intermediate states as well as nonradiative channels. (c) 2005 Elsevier B.V. All rights reserved.