Charge state of vacancy defects in Eu-doped GaN

Mitchell, Brandon; Hernández, Norge Cruz; Lee, D.; Koizumi, Akira; Fujiwara, Yoshihiro; Dierolf, Volkmar

doi:10.1103/physrevb.96.064308

Cited by 22 publications

(11 citation statements)

References 46 publications

(72 reference statements)

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“…The majority center in GaN:Eu, which is referred to as OMVPE4 (Eu1), shows emission around 622 nm and comprises about 90% of the total Eu 3+ ions. Two other important centers known as OMVPE7 (Eu2) and OMVPE8 (Eu2 * ), which have been shown to differ only in charge state for the same defect configuration 8 , show the most pronounced emission under current injection. It is noted that, at room temperature, it is not possible to distinguish OMVPE4 and OMVPE7 (~622 nm), while the peak of OMVPE8 (~618 nm) is easy to isolate.…”

Section: Introductionmentioning

confidence: 99%

Excitation Efficiency and Limitations of the Luminescence of Eu3+ Ions in GaN

et al. 2020

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The excitation efficiency and external luminescence quantum efficiency of trivalent Eu 3+ ions doped into gallium nitride (GaN) was studied under optical and electrical excitation. For small pump fluences it was found that the excitation of Eu 3+ ions is limited by an efficient carrier trap that competes in the energy transfer from the host material. For large pump fluences the limited number of highefficiency Eu 3+ sites, and the small excitation cross-section of the majority Eu 3+ site, limit the quantum efficiency. At low temperatures under optimal excitation conditions, the external luminescence quantum efficiency reached a value of 46%. These results show the high potential for this material as an efficient light emitter, and demonstrates the importance of the excitation conditions on the light output efficiency.

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Section: Introductionmentioning

confidence: 99%

Excitation Efficiency and Limitations of the Luminescence of Eu3+ Ions in GaN

et al. 2020

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“…On the theory side, calculations for Eu-doped GaN were carried out by several research groups using densityfunctional theory (DFT) based methods, including the local-density approximation (LDA) or self-interaction corrected LDA, the generalized gradient approximation (GGA), and GGA+U , and LDA+U within a DFT-based tight-binding approach [33][34][35][36][37][38][39][40][41]. These studies provided useful information on the structural and electronic properties but limited data on defect structure and energetics.…”

Section: Introductionmentioning

confidence: 99%

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

Hoang

2020

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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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“…One concrete example is SiC where charge control of SiV and double-vacancy centers has already been demonstrated, and shown to produce long-lived states [31][32][33] . Another illustration is the family of rare-earth-doped inorganic insulators -of interest for optical information storage 34 due their long-lasting photochromism 35 -and lanthanide-hosting nitrides such as GaN 36 . Similar ideas could be applicable to mid-and low-bandgap semiconductors in situations where thermal activation is insufficient to establish equilibrium (e.g., systems under cryogenic conditions).…”

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confidence: 99%