Optical transitions in Eu3+ ions in GaN:Eu grown by molecular beam epitaxy

Abstract

We report on the photoluminescence, photoluminescence excitation, and cathodoluminescence studies of Eu-doped wurtzite-phase GaN grown by plasma-assisted molecular beam epitaxy. Intra- 4f -transitions of Eu3+ ions starting from the D25, D15, and D05 excited states have been identified and show different thermal quenching in photoluminescence. The D05 → F27 transition at around 620 nm exhibits well-resolved Stark-split emission lines. Depth-sensitive cathodoluminescence and photoluminescence experiments have put in evidence two different sites of Eu3+ ions, one near to the sample surface and the other deeper in the volume, characterized by different crystal-field splitting, thermal quenching, and dependence on optical and electron beam excitations. It is shown that Eu3+ ions located deeper in the volume can be selectively excited by below-band-gap excitation. © 2006 The American Physical Society.