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