Synthesis and characterization of a liquid Eu precursor (EuCppm2) allowing for valence control of Eu ions doped into GaN by organometallic vapor phase epitaxy

Mitchell, Brandon; Koizumi, Akira; Nunokawa, Takumi; Wakamatsu, Ryuta; Lee, D.; Saitoh, Yoichi; Timmerman, Dolf; Kuboshima, Yoshinori; Mogi, Takayuki; Higashi, Shintaro; Kikukawa, Kaoru; Ofuchi, Hironori; Honma, Tetsuo; Fujiwara, Yoshihiro

doi:10.1016/j.matchemphys.2017.02.021

Cited by 13 publications

(9 citation statements)

References 45 publications

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“…Note that our current results for Ln = Eu and Er are in agreement with those we reported previously [18,20]; small discrepancies, if present, can be due to the different versions of the PAW potentials used in the previous and current work. Experimentally, Eu is known to be mixed-valence in GaN, and significant Eu 2+ concentrations (e.g., c(Eu 2+ )/c(Eu 3+ ) > 1) have been achieved in GaN via co-doping with O and Si and tuning the growth conditions [34,35]. As we discussed in detail in Ref.…”

Section: A Defect Energy Levelsmentioning

confidence: 99%

Rare-earth defects in GaN: A systematic investigation of the lanthanide series

Hoang

2022

Preprint

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Rare-earth (RE) doped GaN is of interest for optoelectronics and spintronics and potentially for quantum applications. A fundamental understanding of the interaction between RE dopants and the semiconductor host is key to realizing the material's full potential. This work reports an investigation of lanthanide (Ln) defects in GaN using hybrid density-functional defect calculations. We find that all the Ln dopants incorporated at the Ga lattice site, LnGa (Ln = La-Lu), are stable as trivalent ions, but Eu and Yb can also be stabilized as divalent and Ce, Pr, and Tb as tetravalent. The location of Ln-related defect energy levels and of the Ln 4f states in the energy spectrum of the host material is determined from first principles. We elucidate the interplay between defect formation and electronic structure, including the Ln-N interaction, and the effect of doping on the local lattice environment. Optical properties are investigated by considering possible band-to-defect and defect-to-band transitions involving the LnGa defects. These "charge-transfer" transitions result in broad absorption and emission bands which likely impact the performance of the material.

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Section: A Defect Energy Levelsmentioning

confidence: 99%

Rare-earth defects in GaN: A systematic investigation of the lanthanide series

Hoang

2022

Preprint

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“…1 or 9, thus explain why Eu 3+ is often found to be predominant in Eu-doped GaN samples. A significant Eu 2+ concentration occurs only when prepared under certain conditions [19,20]. Mitchell et al [19], for example, were able to achieve c(Eu 2+ )/c(Eu 3+ ) > 1 when using both O and Si as co-dopants and suitable experimental conditions.…”

Section: A Tuning the Eu Valence And Concentrationmentioning

confidence: 99%

“…A significant Eu 2+ concentration occurs only when prepared under certain conditions [19,20]. Mitchell et al [19], for example, were able to achieve c(Eu 2+ )/c(Eu 3+ ) > 1 when using both O and Si as co-dopants and suitable experimental conditions. The relatively low temperature (e.g., 700 • C instead of 1030 • C) used during growth via OMVPE also appeared to play a key role in increasing the Eu 2+ concentration [19,20,22].…”

Section: A Tuning the Eu Valence And Concentrationmentioning

confidence: 99%

“…Experimentally, while the trivalent Eu 3+ ion was found to be predominant in Eu-doped GaN samples and multiple Eu 3+ luminescence centers were observed [4][5][6][7][8][9][10][11][12], the divalent Eu 2+ has also been found or suspected to be present [13][14][15][16][17][18][19][20]. In addition to being of interest for * khang.hoang@ndsu.edu its magnetic properties [14,15,20], Eu 2+ can offer useful luminescence centers in its own right.…”

Section: Introductionmentioning

confidence: 99%

“…Mitchell et al [19] reported a thorough work on the control of the Eu 2+ /Eu 3+ ratio in GaN through codoping and by tuning the growth conditions and were able to achieve high Eu 2+ concentrations using O and/or Si as co-dopants and suitable experimental conditions. Oxygen was found to play a critical role in the incorporation of Eu into GaN and the quality of Eu-doped GaN samples prepared by organo-metallic vapor phase epitaxy (OMVPE) [19,21] and lead to sharp and uniform emission spectra and improved energy transfer efficiency [19,21,22]. Significant enhancement of the luminescence intensity were also found in GaN co-doped with Eu and Mg [23][24][25][26][27] or Si [28].…”

Section: Introductionmentioning

confidence: 99%

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Tuning the valence and concentration of europium and luminescence centers in GaN through co-doping and defect association

Hoang

2020

Preprint

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Defect physics of Eu-doped GaN is investigated using first-principles hybrid density-functional defect calculations. This includes the interaction between the rare-earth dopant and native defects (Ga and N vacancies) and other impurities (O, Si, C, H, and Mg) unintentionally present or intentionally incorporated into the host material. While the trivalent Eu 3+ ion is often found to be predominant when Eu is incorporated at the Ga site in wurtzite GaN, the divalent Eu 2+ is also stable and found to be predominant in a small range of Fermi-level values in the band-gap region. The Eu 2+ /Eu 3+ ratio can be tuned by tuning the position of Fermi level and through defect association. We find co-doping with oxygen can facilitate the incorporation of Eu into the lattice. The unassociated EuGa is an electrically and optically active defect center and its behavior is profoundly impacted by local defect-defect interaction. Among the Eu-related defects, we identify complexes such as EuGa-ON, EuGa-SiGa, EuGa-Hi, EuGa-MgGa, and EuGa-ON-MgGa as efficient defect-related Eu 3+ centers for non-resonant excitation. This work calls for a re-assessment of certain assumptions regarding specific defect configurations previously made for Eu-doped GaN and further investigation into the origin of the photoluminescence hysteresis observed in (Eu,Mg)-doped samples.

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47‐3: Invited Paper: High Brightness and RGB Integration of Eu‐doped GaN‐based Red LEDs for Ultrahigh‐resolution Micro‐LED Display

Fujiwara

Ichikawa

Timmerman

et al. 2020

Symp Digest of Tech Papers

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A nitride‐based ultra‐small‐size, full‐color, and high‐resolution micro‐LED display is one of key devices for “a smart society”. The ongoing search for an efficient red LED based on GaN is pivotal to the realization of the display. We have worked on the development of semiconductors intracenter photonics. This novel photonics uses the intra‐4f shell transitions of rare‐earth ions doped in semiconductors. In 2009, we invented a narrow‐band red LED using Eu‐doped GaN (GaN:Eu). By continued optimization of the device processing, the output power of the LED is approaching the practical stage. Furthermore, the red LED can be integrated monolithically with conventional blue and green LEDs on the same sapphire substrate. Current status of the GaN:Eu LED and strategies toward further enhancement of its output power using the control of photon fields are reported.

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Synthesis and characterization of a liquid Eu precursor (EuCppm2) allowing for valence control of Eu ions doped into GaN by organometallic vapor phase epitaxy

Cited by 13 publications

References 45 publications

Rare-earth defects in GaN: A systematic investigation of the lanthanide series

Rare-earth defects in GaN: A systematic investigation of the lanthanide series

Tuning the valence and concentration of europium and luminescence centers in GaN through co-doping and defect association

47‐3: Invited Paper: High Brightness and RGB Integration of Eu‐doped GaN‐based Red LEDs for Ultrahigh‐resolution Micro‐LED Display

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