Concentration quenching of Eu-related luminescence in Eu-doped GaN

Abstract

The dependence of Europium (Eu)-related luminescence intensity on the Eu concentration in Eu-doped GaN was studied. This luminescence is observed at 622 nm and originates from the intra-4f transition of the Eu 3+ ion. The intensity of the luminescence increased with increasing Eu concentration, up to about 2 at. %, and then abruptly decreased. It was found that polycrystalline growth began to be induced at Eu concentrations of more than 2 at. %. In addition, clear evidence for the formation of EuN compounds was obtained by x-ray diffraction and extended x-ray absorption fine structure analysis. The cause of the concentration quenching is likely to be related to the polycrystalline growth as well as EuN formation.

Origin of efficient luminescence from GaN:Eu3+ epitaxial films revealed by microscopic photoluminescence imaging spectroscopy

“…[1][2][3][4][5][6] In particular, high-quality GaN is one of the most interesting materials to be used as host crystals for impurity doping and GaN films doped with rare-earth ions are promising materials for light emitters in the visible and infrared spectral regions. [7][8][9][10][11] It has been demonstrated that Eu 3+ -doped GaN ͑GaN:Eu 3+ ͒ epitaxial films exhibit highly efficient red luminescence and stimulated emission due to intra-4f transitions of Eu 3+ ions. 10,11 The spatial distribution of the doped Eu 3+ ions in heavily doped GaN : Eu 3+ films may determine the luminescence properties of such films.…”

“…[7][8][9][10][11] It has been demonstrated that Eu 3+ -doped GaN ͑GaN:Eu 3+ ͒ epitaxial films exhibit highly efficient red luminescence and stimulated emission due to intra-4f transitions of Eu 3+ ions. 10,11 The spatial distribution of the doped Eu 3+ ions in heavily doped GaN : Eu 3+ films may determine the luminescence properties of such films. In fact, spectroscopic studies of the photoluminescence ͑PL͒ properties of GaN:Eu 3+ epitaxial films suggest the presence of several Eu sites that give rise to different peaks in PL spectra.…”

“…10 The Eu 3+ concentration were determined by Rutherford backscattering spectrometry and energy dispersive x-ray spectroscopy. The Eu 3+ ions are almost uniformly doped in the epitaxial films.…”

“…10,11 Figure 1 shows the spatial images of the spectrally integrated PL intensity from 615 to 635 nm for four samples having different Eu 3+ concentrations: ͑a͒ 0.1, ͑b͒ 1, ͑c͒ 3, and ͑d͒ 8 at. % under 3.81 eV excitation at room temperature.…”

“…%. 10 In the high concentration sample ͓Fig. 1͑d͔͒, the reduction in the PL intensity is spatially uniform.…”