Optical investigations of europium ion implanted in nitride-based diode structures

Sédrine, N. Ben; Rodrigues, Joana; Cardoso, J.; Faye, Djibril; Fialho, M.; Magalhães, S.; Martins, A. F.; Neves, A.J.; Alves, E.; Boćkowski, Michał; Hoffmann, Veit; Weyers, M.; Lorenz, K.; Correia, M. R.; Monteiro, T.

doi:10.1016/j.surfcoat.2018.02.004

Cited by 9 publications

(9 citation statements)

References 19 publications

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“…Indeed, this absorption is enhanced with the increase of the fluence, confirming an increase in the density of irradiation-induced defects (i.e., a higher number of states in the bandgap obtained for the highest fluence), accompanied by a redshift of E CPPB as seen from the absorption below the ZnO bandgap. This enhanced absorption below the bandgap due to irradiation or implantation-induced defects has already been reported in other wide-bandgap semiconductors such as III-nitrides [46,47].…”

Section: Discussionsupporting

confidence: 74%

Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation

et al. 2019

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Here, we report on the production of nanoripples on the surface of ZnO bulk substrates by ion beam erosion with 20 keV Ar + ions at an oblique incidence (60 • ). The ripple patterns, analyzed by atomic force microscopy, follow a power law dependence for both the roughness and the wavelength. At high fluences these ripples show coarsening and asymmetric shapes, which become independent of the beam direction and evidence additional mechanisms for the pattern development. The shallow damaged layer is not fully amorphized by this process, as confirmed by medium energy ion scattering. A detailed study of the damage-induced changes on the optical properties was carried out by means of spectroscopic ellipsometry. Using a 3-layer model based on Tauc-Lorenz and critical point parameter band oscillators, the optical constants of the damaged layer were determined. The results showed a progressive reduction in the refractive index and enhanced absorption below the bandgap with the fluence.Crystals 2019, 9, 453 2 of 12 with identical crystal structure (wurtzite) and are suitable for applications in optoelectronics, including the fabrication of light emitting diodes and laser diodes [7,8]. However, since commercial GaN-based devices are already available in the global market, considerable interest has shifted to other potential uses of ZnO.The existing reports on the surface modification of ZnO mainly refer to focused ion beams [9] or laser ablation processes [10]. Only recently, some works have reported ripple formation on ZnO when implanting with 10 keV O + ions [11]. More research is needed to understand the physical processes that take place when this kind of radiation resistant material is irradiated, especially with respect to the damage formation and the particular role of preferential sputtering. In this regard, there is also a lack of reliable optical models to explain the evolution of the damage in these semiconductors, which can be helpful to monitor the implantation effects. One technique able to provide such information is spectroscopic ellipsometry (SE), which has been used for the determination of damage profiles in different semiconductors, such as Si [12] or GaAs [13]. However, these models are very specific for every semiconductor and do not take into account the development of very rough surfaces during the implantation: the typical case when producing ripple patterns at high fluences.Considering this scenario, the main goal of this work was to assess the formation of ripple patterns in bulk ZnO by IBS at medium energy (20 keV) using Ar + ions. We analysed the ripple patterns produced by oblique irradiation regarding the roughness, ripple wavelength, and order. In order to evaluate the ion beam modification of the material, we took advantage of SE to model both the optical damage and the roughening of the surface, and to extract the main optical parameters after the irradiation. Materials and MethodsBulk c-plane one-side polished ZnO crystals (supplied by CrysTec and produced by hydrothermal synthesis, Berli...

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Section: Discussionsupporting

confidence: 74%

Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation

et al. 2019

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“…When the Eu fluence increases up to 1 × 10 15 Eu·cm –2 (stars), the color emission becomes red and almost independent of temperature, exhibiting higher thermal color stability than the Eu14 sample. We have recently reported that, unlike GaN layers, the use of the 325 nm excitation was found to be the most efficient photoexcitation for providing the perceived red emission in nitride-based diode structure …”

Section: Resultsmentioning

confidence: 99%

“…We have recently reported that, unlike GaN layers, the use of the 325 nm excitation was found to be the most efficient photoexcitation for providing the perceived red emission in nitridebased diode structure. 70 Photoluminescence Excitation. It is well established that the Eu 3+ intraionic emission possesses different sensitivities to above and below bandgap excitations, as observed in Euimplanted GaN layers.…”

Section: Acs Applied Nano Materialsmentioning

confidence: 99%

Eu-Doped AlGaN/GaN Superlattice-Based Diode Structure for Red Lighting: Excitation Mechanisms and Active Sites

Sédrine

Rodrigues

Faye³

et al. 2018

ACS Appl. Nano Mater.

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In this work, we have established the effects of postgrowth annealing and Eu implantation, followed by annealing on an AlGaN/GaN superlattice-based diode structure, containing Mg-doped GaN top p-cap layers. The study is based on the combined information from different optical techniques, such as Raman, photoluminescence, and photoluminescence excitation. We have shown that the diode structure exhibits a stable crystalline quality even after annealing under high temperature and high pressure (HTHP) conditions (1400°C in 1 GPa N 2 ). Furthermore, we have demonstrated that the implanted Eu ions reached the first quantum wells of the diode structure and that the postimplantation thermal annealing partly removed the implantation defects, recovering some of the as-grown luminescence and optically activating the Eu 3+ in the diode structure. An in-depth study of the Eu 3+ population mechanisms was realized through room temperature photoluminescence excitation. A model was built based on the different excitation bands originated from the materials present in the diode structure, demonstrating that an energy transfer between the AlGaN/GaN superlattice excitons and the Eu 3+ ions occurs, therefore enlarging the excitation pathways for the ion's red luminescence. In addition, Eu 3+ luminescence was observed not only with above but also with below GaN bandgap excitation. The temperature dependent study of the 5 D J → 7 F J transitions allowed to tentatively provide the Eu 3+ intraionic assignments of the diode structure. We have demonstrated that at least three nonequivalent active sites are created by the Eu implantation in the diode structure: Eu1, Eu2, and Eu−Mg defect in both configurations Eu0 and Eu1(Mg).

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“…As an alternative to in situ RE incorporation, ex-situ ion implantation constitutes a suitable method to obtain a controlled doping profile with concentration even beyond solubility limits [18,25,26,32,[42][43][44][45][46][47]. This technique requires post-implantation thermal annealing to recover the implantation-induced damage and to optically activate the RE ions.…”

Section: Introductionmentioning

confidence: 99%

Eu3+ optical activation engineering in Al Ga1-N nanowires for red solid-state nano-emitters

Cardoso

Jacopin

Faye

et al. 2021

Applied Materials Today

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In this work, Eu 3+ -implanted and annealed AlxGa1-xN (0 ≤ x ≤ 1) nanowires (NWs) grown on GaN NW template on Si (111) substrates by plasma-assisted molecular beam epitaxy are studied by µ-Raman, cathodoluminescence (CL), nano-CL, and temperature-dependent steady-state photoluminescence. The preferential location of the Eu 3+ -implanted ions is found to be at the AlxGa1-xN top-section. The recovery of the as-grown crystalline properties is achieved after rapid thermal annealing (RTA). After RTA, the red emission of the Eu 3+ ions is attained for all the samples with below and above bandgap excitation. The 5 D0 → 7 F2 transition is the most intense one, experiencing a redshift with increasing AlN nominal content (x) from GaN to AlN NWs. Moreover, AlN nominal content and annealing temperature alters its spectral shape suggesting the presence of at least two distinct optically active Eu 3+ centers (Eu1 and Eu2). Thermal quenching of the Eu 3+ ion luminescence intensity, I, is found for all the samples from 14 K to 300 K, being the emission of Eu 3+ -implanted AlN NWs after RTA at 1200 ℃ the most stable (I300 K/I14 K ~80%). The GaN/AlN interface in this sample is also found to have a key role in the Eu 3+ optical activation.

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Optical investigations of europium ion implanted in nitride-based diode structures

Cited by 9 publications

References 19 publications

Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation

Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation

Eu-Doped AlGaN/GaN Superlattice-Based Diode Structure for Red Lighting: Excitation Mechanisms and Active Sites

Eu3+ optical activation engineering in Al Ga1-N nanowires for red solid-state nano-emitters

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