Emission enhancement mechanism of GaN:Eu by Mg codoping

Mg codoping into Eu-doped GaN strongly affects the two dominant optical sites A (620.3 nm) and B (622.3 nm) and dramatically improves the optical characteristics obtained from Eu3+ ions. To clarify the mechanism of the enhanced emission, the effects of the Mg concentration on the excitation and emission processes were evaluated by considering the excitation power dependence of photoluminescence (PL) and time-resolved PL at various temperatures. The excitation cross section sigma(ex), which reflected the excitation process, did not depend on the Mg concentration but strongly on the optical site, which was attributed to the different energy transfer processes of the two optical sites. sigma(ex) for site A was three times larger than that for site B, indicating higher excitation efficiency for site A. Mg codoping dramatically increased the number of Eu ions in site A that remain active at room temperature (RT) and the D-5(0) lifetime at RT, indicating the suppression of nonradiative components during the emission process. Therefore, the optical properties were markedly enhanced by Mg codoping. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772950]