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(321) Production(s) de GIL B.
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The microstructure, local indium composition and photoluminescence in green-emitting InGaN/GaN quantum wells
Auteur(s): Chery Nicolas, Ngo T. H., Chauvat M.P., Damilano B., Courville A, Ruterana Pierre, Gil B., de Mierry P., Grieb Tim, Mehrtens Thorsten, Krause Florian, Müller-Caspary Knut, Schowalter Marco, Rosenauer Andreas
(Article) Publié:
Journal Of Microscopy, vol. 268 p.305-313 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01691523_v1
DOI: 10.1111/jmi.12657
WoS: 000415900300012
Exporter : BibTex | endNote
1 Citation
Résumé: In this work, we analyse the microstructure and local chemical composition of green-emitting InxGa1-xN/GaN quantum well (QW) heterostructures in correlation with their emission properties. Two samples of high structural quality grown by metalorganic vapour phase epitaxy (MOVPE) with a nominal composition of x = 0.15 and 0.18 indium are discussed. The local indium composition is quantitatively evaluated by comparing scanning transmission electron microscopy (STEM) images to simulations and the local indium concentration is extracted from intensity measurements. The calculations point out that the measured indium fluctuations may be correlated to the large width and intensity decrease of the PL emission peak.
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Isotope engineering of van der Waals interactions in hexagonal boron nitride
Auteur(s): Vuong P., Liu S., van Der Lee A., Cusco R., Artus L., Michel T., Valvin P., Edgar J. H., Cassabois G., Gil B.
(Article) Publié:
Nature Materials, vol. 17 p.152 (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01675183_v1
DOI: 10.1038/nmat5048
WoS: 000423153800014
Exporter : BibTex | endNote
41 Citations
Résumé: Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes ( 10 B and 11 B) compared to those with the natural distribution of boron (20 at% 10 B and 80 at% 11 B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers in 10 BN than in 11 BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.
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Quantum Dot based UV Light Emitting Diodes
Auteur(s): Brault Julien, Matta S., Al Khalfioui Mohamed, Leroux Mathieu, Damilano Benjamin, Chenot S., Korytov M, Peyre H., Konczewicz L., Contreras S., Chaix C., Massies Jean, Gil B.
(Affiches/Poster)
12th international conference on nitride semiconductors (STRASBOURG, FR), 2017-07-24
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High temperature electrical transport study of n-type Si-doped AlN
Auteur(s): Contreras S., Konczewicz L., Peyre H., Juillaguet S., Weyher J.l., Dziecielewski I, Al khalfioui Mohamed, Matta S., Leroux Mathieu, Damilano Benjamin, Brault Julien, Gil B.
(Affiches/Poster)
International Workshop on Ultraviolet Materials and Devices (FUKUOKA, JP), 2017-11-14
Résumé: High temperature electrical transport study of n-type Si-doped AlN
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Influence of the heterostructure design on the optical properties of GaN and Al0.1Ga0.9N quantum dots for ultraviolet emission
Auteur(s): Matta S., Brault Julien, Ngo T. H., Damilano B., Korytov Maxim, Vennegues P, Nemoz Maud, Massies Jean, Leroux Mathieu, Gil B.
(Article) Publié:
Journal Of Applied Physics, vol. 122 p.085706 (2017)
Ref HAL: hal-01579358_v1
DOI: 10.1063/1.5000238
WoS: 000409117200061
Exporter : BibTex | endNote
9 Citations
Résumé: The optical properties of AlyGa1-yN quantum dots (QDs), with y 1⁄4 0 or y 1⁄4 0.1, in an AlxGa1 xN matrix are studied. The influence of the QD layer design is investigated pointing out the correlations between the QD structural and optical properties. In a first part, the role of the epitaxial strain in the dot self-assembling process is studied by fabricating GaN QD layers on different AlxGa1 xN layers with 0.5 x 0.7. Photoluminescence (PL) measurements show the main influ- ence of the increase of the internal electric field (Fint) on the QD optical response inducing a strong red shift in the emission energy as x increases. Time resolved combined with temperature depen- dent PL measurements enabled the estimation of the QD internal quantum efficiencies at low tem- perature showing values around 50%. In addition, a PL integrated intensity ratio up to 74% is shown, between 300 and 9 K. In the second part, the design of Al0.1Ga0.9N QDs was investigated, by varying the Al0.1Ga0.9N amount deposited. An increase of the transition energy (from 3.65 eV up to 3.83eV) is obtained while decreasing the deposited amount. Calculations of the ground state transition energies as a function of the Al0.1Ga0.9N dot height give a value of Fint around 2.060.5MV/cm. Therefore, the propensity of Al0.1Ga0.9N dots to emit at much higher energies than GaN dots (a PL shift of 1 eV using a low excitation power) is seen as the consequence of the reduced Fint together with their smaller sizes.
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Photo-induced droop in blue to red light emitting InGaN/GaN single quantum wells structures
Auteur(s): Ngo T. H., Gil B., Damilano Benjamin, Valvin P., Courville A, Demierry P
(Article) Publié:
Journal Of Applied Physics, vol. 122 p.063103 (2017)
Ref HAL: hal-01573934_v1
DOI: 10.1063/1.4997608
WoS: 000407742400003
Exporter : BibTex | endNote
9 Citations
Résumé: The variation of the internal quantum efficiency (IQE) of single InGaN quantum well structures emitting from blue to red is studied as a function of the excitation power density and the temperature. By changing the well width, the indium content, and adding a strain compensation AlGaN layer, we could tune the intrinsic radiative recombination rate by changing the quantum confined Stark effect, and we could modify the carrier localization. Strong quantum confined Stark effect and carrier localization induce an increase in the carrier density and then favor Auger non-radiative recombination in the high excitation range. In such high excitation conditions with efficient Auger recombination, the variation of the IQE with the photo-excitation density P is ruled by a universal power law independent of the design: IQE = IQEMAX – a log10P with a close to 1/3. The temperature dependences of the different recombination mechanisms are determined. At low temperature, both quantum confined Stark effect and carrier localization trigger electron-electron repulsions and therefore the onset of the Auger effect. The increase in the value of coefficient C with changing temperature reveals indirect Auger recombination that relates to the interactions of the carriers with other phonons than the longitudinal optical one.
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Exciton-phonon interaction in the strong-coupling regime in hexagonal boron nitride
Auteur(s): Vuong P., Cassabois G., Valvin P., Liu Song, Edgar Jim, Gil B.
(Article) Publié:
Physical Review B, vol. 95 p.201202(R) (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01528598_v1
DOI: 10.1103/PhysRevB.95.201202
WoS: 000402051300001
Exporter : BibTex | endNote
13 Citations
Résumé: The temperature-dependent optical response of excitons in semiconductors is controlled by the exciton-phonon interaction. When the exciton-lattice coupling is weak, the excitonic line has a Lorentzian profile resulting from motional narrowing, with a width increasing linearly with the lattice temperature T . In contrast, when the exciton-lattice coupling is strong, the line shape is Gaussian with a width increasing sublinearly with the lattice temperature, proportional to sqrt(T) . While the former case is commonly reported in the literature, here the latter is reported for hexagonal boron nitride. Thus the theoretical predictions of Toyozawa [Prog. Theor. Phys. 20, 53 (1958)] are supported by demonstrating that the exciton-phonon interaction is in the strong-coupling regime in this van der Waals crystal.
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