Site specific Eu3+ stimulated emission in GaN host

Abstract

We report the observation of site-specific Eu 3+ stimulated emission in GaN:Eu laser structures. Two main Eu sites have been identified from emission peaks associated with the 5 D 0 → 7 F 2 transition during above band gap optical pumping with a pulsed N 2 laser ͑337 nm͒: ͑a͒ Eu x emitting at ϳ620 nm-present in short cavities ͑ϳ100 m͒, exhibiting stimulated ͑side͒ emission threshold and a fast decay time constant ͑30-35 s͒; ͑b͒ Eu y emitting at ϳ621 nm-present in long cavities ͑ϳ7 mm͒ and in surface emission, exhibiting no stimulated emission threshold and a slow decay time constant ͑150-250 s͒.

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

“…On the other hand, the PL peak at 633.5 nm is due to the energy shift of the 5 D 0 − 7 F 2 transition or of the 5 D 1 − 7 F 4 transition. 11,12,15 The Eu 3+ concentration and the excitation energy dependences of the PL spectral shape clearly show that there are several Eu 3+ sites having different local environments. In particular, the intensities of the PL peaks denoted by indices ␣, ␤, and ␥ ͑I ␣ , I ␤ , and I ␥ ͒ in the figure are sensitive to the Eu 3+ concentration and the excitation energy.…”

“…[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.…”

“…10,11 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.…”

Luminescence spectroscopy of Eu‐implanted zincblende GaN

“…The optically active centres are therefore likely to be structurally similar RE Ga -intrinsic defect complexes. Recently, Park and Steckl reported that two different Eu 3+ sites are involved in stimulated emission (lasing) in W-GaN:Eu optical cavities [5]. A reported blue-shift of the dominant Eu 3+ peak in W-GaN powder, to 611 nm, ascribed to the existence of stacking faults and cubic structures [6], was not reproduced in later work [7]; moreover, aggregation of nanocrystalline powder into micrometer-sized conglomerates reportedly causes a significant red-shift of Eu 3+ emission spectra [8].…”