GaN:Eu electroluminescent devices grown by interrupted growth epitaxy

Munasinghe, C.; Steckl, A. J.

doi:10.1016/j.tsf.2005.08.328

Cited by 19 publications

(11 citation statements)

References 18 publications

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“…exhibits the highest concentration of this site, this sample should produce the highest electroluminescence. This was verified by Munasinghe, et al [4] in their EL measurements of the IGE samples. It should be noted that the defecttrap related site appears very weak under resonant excitation; even under optimum growth conditions the relative emission intensity with respect to the majority site is 1:5.…”

Section: Experimental Technique the Energy Levels Of The Eusupporting

confidence: 69%

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Identification of defect‐trap‐related europium sites in gallium nitride

Fleischman

Tafon

Dierolf

et al. 2007

Phys. Status Solidi (c)

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We performed site-selective combined excitation-emission spectroscopy (CEES) studies on Eu-doped GaN layers grown using Interrupted Growth Epitaxy (IGE). We identified numerous Eu 3+ incorporation sites, which exhibit different relative emission intensities as the growth conditions are varied. We found defecttrap related Eu sites that can be excited over a wide spectral range and that dominate the photoluminescence spectra for above-bandgap excitation. Spectra obtained through above-bandgap excitation, which simulates EL operation, are identical to the emission spectra of these defect-trap related sites, indicating that these particular Eu ions would be the major contributors to electroluminescent (EL) emission in these samples. In resonant excitation, however, the emission from these sites is rather weak suggesting that these are minority sites.1 Introduction GaN is one of the most promising semiconductor hosts for rare-earth (RE) based light emitters. It can provide carrier generation to excite the RE, it is transparent to visible RE emission, and it is thermally and chemically rugged. The wide-bandgap and the ability to tailor the bandgap through III-N alloying enable matching this material system to many RE 3+ ions. Electroluminescence from GaN doped with Er, Eu, Pr, Tb, Tm and other REs has been reported [1] exhibiting sharp emission lines from the UV to the near IR. Red, green, and blue light emission is possible with the incorporation of the appropriate REs into GaN, meaning the realization of full color displays operating under a variety of conditions is possible with this host material. Moreover, laser action in Eu-doped GaN has been reported under optical excitation [2], rekindling the hope that an electrically-pumped rare-earth-doped semiconductor laser can be realized.In the pursuit of this goal, it becomes important that all rare-earth ions that are in the laser cavity are effectively excited. The presence of multiple RE incorporation sites can complicate matters by introducing different excitation pathways, which can be site-specific. The overall distribution of these different incorporation sites can be controlled by adjusting the conditions of the GaN growth. To optimize these devices for laser operation requires the detailed characterization of the RE incorporation sites in terms of their energy states and their capability to be electrically excited. Of particular interest would be the study of Eu sites that are strongly coupled to defect or impurity traps, as they would have a high capture cross section for free carriers (trap-mediated excitation) and would be efficiently excited by above-bandgap excitations [3]. This is important because above-gap optical excitation simulates the electron-hole pair pumping that occurs during electrical injection of p-n junction diodes.In this work, we address the task of characterizing the different Eu-incorporation sites over a range of GaN layers that have varying crystal growth parameters, using the site-selective technique of combined excitation-emission sp...

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Section: Experimental Technique the Energy Levels Of The Eusupporting

confidence: 69%

“…2 Sample information Our GaN:Eu samples were grown by the Interrupted Growth Epitaxy (IGE) technique developed at the University of Cincinnati [4]. IGE, is a modification of conventional MBE where the Group III beams (Ga, RE 3+ ) are cycled ON and OFF while the Group V beam (N) is maintained constantly.…”

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confidence: 99%

Identification of defect‐trap‐related europium sites in gallium nitride

Fleischman

Tafon

Dierolf

et al. 2007

Phys. Status Solidi (c)

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“…% at ϳ70 nm depth. A second set of samples ͑Table II͒ was grown by MBE with the interrupted growth epitaxy ͑IGE͒ technique, 19,20 for which the shutters of group III elements ͑Ga and Eu͒ are open ͑"on"͒ for a part of the cycle and close ͑"off"͒ for the rest of the time. The group V is on throughout the entire IGE cycling time.…”

Section: Samples and Measurementsmentioning

confidence: 99%

Optically active centers in Eu implanted, Eu in situ doped GaN, and Eu doped GaN quantum dots

Bodiou

Braud

Doualan

et al. 2009

Journal of Applied Physics

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A comparison is presented between Eu implanted and Eu in situ doped GaN thin films showing that two predominant Eu sites are optically active around 620 nm in both types of samples with below and above bandgap excitation. One of these sites, identified as a Ga substitutional site, is common to both types of Eu doped GaN samples despite the difference in the GaN film growth method and in the doping technique. High-resolution photoluminescence (PL) spectra under resonant excitation reveal that in all samples these two host-sensitized sites are in small amount compared to the majority of Eu ions which occupy isolated Ga substitutional sites and thus cannot be excited through the GaN host. The relative concentrations of the two predominant host-sensitized Eu sites are strongly affected by the annealing temperature for Eu implanted samples and by the group III element time opening in the molecular beam epitaxy growth. Red luminescence decay characteristics for the two Eu sites reveal different excitation paths. PL dynamics under above bandgap excitation indicate that Eu ions occupying a Ga substitutional site are either excited directly into the D50 level or into higher excited levels such as D51, while Eu ions sitting in the other site are only directly excited into the D50 level. These differences are discussed in terms of the spectral overlap between the emission band of a nearby bound exciton and the absorption bands of Eu ions. The study of Eu doped GaN quantum dots reveals the existence of only one type of Eu site under above bandgap excitation, with Eu PL dynamics features similar to Eu ions in Ga substitutional sites.

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“…Hole concentration as high as 4.5 Â 10 18 cm À3 with an accompanying mobility of 1.2 cm 2 /VÁs has been achieved with MME. 10 MME and other similar growth schemes, [11][12][13][14] such as metal enhanced epitaxy (MEE), 11 alternatively saturate the surface with Ga and N fluxes, so that good quality film is achieved even at relatively low growth temperatures.…”

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confidence: 99%

“…The dopant shutter schedule is designed to be open during a specific period of time in each cycle so that the dopant is introduced only when the surface is either Ga-rich or N-rich. The timing sequences of different dynamic growth schemes 10,12,13 are shown in Fig. 1.…”

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confidence: 99%