Effect of thermal annealing on luminescence properties of Eu,Mg-codoped GaN grown by organometallic vapor phase epitaxy

The effects of thermal annealing on Eu,Mg-codoped GaN (GaN:Eu,Mg) grown by organometallic vapor phase epitaxy were investigated. After annealing in nitrogen ambient, Eu-Mg related photoluminescence emission was quenched to 13% without a change in the spectral shape. The quenched emission recovered to 65% of the original intensity after a subsequent annealing in ammonia ambient. Combined excitation emission spectroscopy and time-resolved photoluminescence results revealed that the quenching behavior is attributed to a nonradiative process induced by unpassivated Mg acceptors in the relaxation of excited 4f electrons of Eu ions.