High pressure luminescence studies of europium doped GaN

We reported on the high pressure luminescence spectra of polycrystalline Eu-doped GaN material synthesized in the reaction between alloys of gallium, bismuth and europium in ammonia atmosphere. The integrated luminescence intensity of the dominant Eu3+ ion transition (D-5(0)-> F-7(2)) at 622 nm increased approximately one order of magnitude whereas its spectral position and line width did not change significantly between ambient and 6.8 GPa pressure, respectively. Moreover, material was characterized with photo- and cathodo-luminescence, and photoluminescence excitation spectra at different temperatures. It was found that the Eu3+ ions occupying substitutional Ga site created different centers which could be effectively excited with above band gap excitation and from excitons resonantly photoexcited at the I-2 bound exciton energy. Furthermore, the less efficient Eu3+ ions excitation path existed through intrinsic impurities and defects generating shallow energy levels in the forbidden gap. It was proposed that reduction of the thermal quenching and consequent enhancement of Eu3+ ion emission intensity resulted from stronger localization of bound exciton on RESI trap induced by applied pressure.