Site specific Eu[sup 3+] stimulated emission in GaN host (original) (raw)

Effect of optical excitation energy on the red luminescence of Eu[sup 3+] in GaN

Applied Physics Letters, 2005

Photoluminescence ͑PL͒ excitation spectroscopy mapped the photoexcitation wavelength dependence of the red luminescence ͑ 5 D 0 → 7 F 2 ͒ from GaN:Eu. Time-resolved PL measurements revealed that for excitation at the GaN bound exciton energy, the decay transients are almost temperature insensitive between 86 K and 300 K, indicating an efficient energy transfer process. However, for excitation energies above or below the GaN bound exciton energy, the decaying luminescence indicates excitation wavelength-and temperature-dependent energy transfer influenced by intrinsic and Eu 3+ -related defects.

Spectroscopic and energy transfer studies of Eu[sup 3+] centers in GaN

Journal of Applied Physics, 2007

Photoluminescence ͑PL͒, photoluminescence excitation ͑PLE͒, and time-resolved PL spectroscopies have been carried out at room temperature and 86 K on transitions from 5 D 2 , 5 D 1 , and 5 D 0 excited states to numerous 7 F J ground states of Eu-doped GaN films grown by conventional solid-source molecular beam epitaxy ͑MBE͒ and interrupted growth epitaxy MBE. Within the visible spectral range of 1.8-2.7 eV, 42 spectral features were observed and assignments were attempted for each transition. PL and PLE indicate that four Eu 3+ centers exist in the GaN lattice whose relative concentration can be controlled by the duration of growth interruption. The energy levels for these four sites are self-consistently obtained, and time-resolved photoluminescence measurements reveal details about the radiative and nonradiative relaxations of excitation among these levels. The data indicate a near-resonant cross relaxation among these sites. The 5 D 2 and 5 D 1 states are observed to decay nonradiatively by filling the 5 D 0 state with characteristic times of 2.4 and 2.8 s, respectively. The 5 D 0 state is found to relax in a manner that depends slightly on the final state and dopant site.

Spectroscopic and energy transfer studies of Eu 3+ centers in GaN

Effect of optical excitation energy on the red luminescence of Eu 3+ in GaN

Laser action in Eu-doped GaN thin-film cavity at room temperature

Applied Physics Letters, 2004

Rare-earth-based lasing action in GaN is demonstrated. Room-temperature stimulated emission (SE) was obtained at 620 nm from an optical cavity formed by growing in situ Eu-doped GaN thin films on sapphire substrates. The SE threshold for optical pumping of a ϳ1 at. % Eu-doped GaN sample was ϳ10 kW/ cm 2 . The SE threshold was accompanied by reductions in the emission linewidth and lifetime. A modal gain of ϳ43 cm −1 and a modal loss of ϳ20 cm −1 were obtained.

Effect of growth conditions on Eu3+ luminescence in GaN

Journal of Crystal Growth, 2010

Eu-doped GaN thin films were in situ grown on sapphire substrates by RF plasma-assisted solid-source molecular beam epitaxy technique. Strong red emission at $ 622 nm from 5 D 0 -7 F 2 radiative transitions in Eu 3 + ions was observed for all samples. The effects of important growth parameters, such as III/V ratio (Ga flux), Eu cell temperature (Eu flux) and growth temperature, on Eu 3 + photoluminescence were studied. X-ray diffraction and secondary ion mass spectroscopy measurements were performed to investigate thin film quality and Eu doping profiles. The strongest Eu 3 + luminescence was obtained from GaN:Eu thin films grown under slightly N-rich condition (III/V o 1), while the highest Eu 3 + emission efficiency was obtained in thin films grown under Ga-rich condition (III/V Z 1). The optimum Eu doping concentration for Eu 3 + luminescence is $ (0.1-1.0) at% for III/V r 1 ratio condition. Higher growth temperature ( 4 750 1C) was also found to enhance Eu 3 + luminescence intensity and efficiency.

The role of donor-acceptor pairs in the excitation of Eu-ions in GaN: Eu epitaxial layers

The nature of Eu incorporation and resulting luminescence efficiency in GaN has been extensively investigated. By performing a comparative study on GaN:Eu samples grown under a variety of controlled conditions, and using a variety of experimental techniques, the configuration of the majority site has been concluded to contain a nitrogen vacancy (V N). The nitrogen vacancy can appear in two symmetries, which has a profound impact on the luminescence and magnetic properties of the sample. The structure of the minority site has also been identified. We propose that, for both sites, the excitation efficiency of the red Eu emission is improved by the presence of donor-acceptor pairs in the close vicinity of the Eu. V

Effect of Si codoping on Eu[sup 3+] luminescence in GaN

Journal of Applied Physics, 2009

Eu and Si codoped GaN thin films were grown on sapphire by solid source molecular beam epitaxy. Eu 3+ photoluminescence ͑PL͒ emission at ϳ622 nm ͑ 5 D 0 -7 F 2 ͒ was enhanced by approximately five to ten times with Si doping. The effect of Si codoping on PL intensity, lifetime, and excitation dependence revealed two distinct regimes. Moderate Si doping levels ͑0.04-0.07 at. %͒ lead to an increase in lifetime combined with improved excitation efficiency and a greatly enhanced PL intensity. High Si doping levels ͑0.08-0.1 at. %͒ significantly quench the PL intensity and lifetime, due primarily to nonradiative channels produced by a high defect population.

Site specific Eu[sup 3+] stimulated emission in GaN host (original) (raw)

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