Accueil >
Production scientifique
(321) Production(s) de GIL B.
|
|
Hexagonal boron nitride is an indirect bandgap semiconductor
Auteur(s): Cassabois G., Valvin P., Gil B.
(Article) Publié:
Nature Photonics, vol. 10 p.262 (2016)
Texte intégral en Openaccess :
Ref HAL: hal-01261847_v1
DOI: 10.1038/nphoton.2015.277
WoS: 000372978900017
Exporter : BibTex | endNote
476 Citations
Résumé: Hexagonal boron nitride is a wide bandgap semiconductor with a very high thermal and chemical stability used in devices operating under extreme conditions. The growth of high-purity crystals has recently revealed the potential of this material for deep ultraviolet emission, with an intense emission around 215 nm. In the last few years, hexagonal boron nitride has been raising even more attention with the emergence of two-dimensional atomic crystals and Van der Waals heterostructures, initiated with the discovery of graphene. Despite this growing interest and a seemingly simple structure, the basic questions of the bandgap nature and value are still controversial. Here, we resolve this long-debated issue by bringing the evidence for an indirect bandgap at 5.955 eV by means of optical spectroscopy. We demonstrate the existence of phonon-assisted optical transitions, and we measure an exciton binding energy of about 130 meV by two-photon spectroscopy.
|
|
|
Optical properties of hexagonal boron nitride
Auteur(s): Cassabois G., Valvin P., Gil B.
Conference: Discussions Lavoisier: Nouveaux matériaux bidimensionnels (Toulouse, FR, 2015-09-24)
Ref HAL: hal-01281934_v1
Exporter : BibTex | endNote
Résumé: In this paper, I will review our recent results demonstrating that hBN has an indirect bandgap at 5.9 eV. I will show that the optical properties of hBN are profoundly determined by phonon-assisted transitions with a mirror symmetry between emission and absorption around the indirect exciton at 5.9 eV (Figure 1). I will provide a comprehensive analysis of the emission spectrum in the deep ultraviolet in terms of phonon-assisted transitions involving either virtual or real excitonic states, the latter being provided by structural defects. I will finally point out the complex relaxation dynamics of the quantum gas formed by the reservoir of indirect excitons.
|
|
|
Optical properties of hexagonal boron nitride
Auteur(s): Cassabois G., Valvin P., Gil B.
Conférence invité: 11th International Conference on Nitride Semiconductors (ICNS11) (Beijing, CN, 2015-08-31)
Ref HAL: hal-01281931_v1
Exporter : BibTex | endNote
Résumé: In this paper, I will review our recent results demonstrating that hBN has an indirect bandgap at 5.9 eV. I will show that the optical properties of hBN are profoundly determined by phonon-assisted transitions with a mirror symmetry between emission and absorption around the indirect exciton at 5.9 eV (Figure 1). I will provide a comprehensive analysis of the emission spectrum in the deep ultraviolet in terms of phonon-assisted transitions involving either virtual or real excitonic states, the latter being provided by structural defects. I will finally point out the complex relaxation dynamics of the quantum gas formed by the reservoir of indirect excitons.
|
|
|
Intervalley scattering in hexagonal boron nitride
Auteur(s): Cassabois G., Valvin P., Gil B.
(Article) Publié:
Physical Review B, vol. 93 p.035207 (2016)
DOI: 10.1103/PhysRevB.93.035207
WoS: 000369221000004
43 Citations
Résumé: We report photoluminescence experiments bringing the evidence for intervalley scattering in bulk hexagonal boron nitride. From a quantitative analysis of the defect-related emission band, we demonstrate that transverse optical phonons at the K point of the Brillouin zone assist inter-K valley scattering, which becomes observable because stacking faults in bulk hexagonal boron nitride provide a density of final electronic states. Time-resolved experiments highlight the different recombination dynamics of the phonon replicas implying either virtual excitonic states or real electronic states in the structural defects.
Commentaires: Editors' suggestion:
The authors have conducted an experimental study of hexagonal boron nitride using steady-state and time-resolved photoluminescence. The assignment of previously observed lines of unknown origin is made convincingly to indirect excitons assisted by acoustic and optical phonons and to defect-assisted transitions. This is further evidence for h-BN being an indirect band-gap semiconductor.
|
|
|
Temperature-dependent time-resolved photoluminescence measurements of (1-101)-oriented semi-polar AlGaN/GaN MQWs
Auteur(s): Rosales D., Gil B., Monavarian Morteza, Zhang Fan, Okur Serdal, Izyumskaya Natalia, Avrutin Vitaliy, Oezguer Uemit, Morkoc Hadis
Conference: GALLIUM NITRIDE MATERIALS AND DEVICES X (san francisco, US, 2015)
|
|
|
Photoluminescence behavior of amber light emitting GaInN-GaN heterostructures
Auteur(s): Ngo T. H., Rosales D., Gil B., Valvin P., Damilano Benjamin, Lekhal Kaddour, de Mierry Philippe
Conference: GALLIUM NITRIDE MATERIALS AND DEVICES X (san francisco, US, 2015)
|
|
|
Excitation-dependent carrier dynamics in Al-rich AlGaN layers and multiple quantum wells
Auteur(s): Šcajev Patrik, Miasojedovas Saulius, Jarasiunas Kestutis, Hiramatsu Kazumaza, Miyake Hideto, Gil B.
(Article) Publié:
Physica Status Solidi A, vol. 252 p.1043-1049 (2015)
Texte intégral en Openaccess :
Ref HAL: hal-01238741_v1
DOI: 10.1002/pssb.201451479
WoS: WOS:000354267300032
Exporter : BibTex | endNote
5 Citations
Résumé: .The combined temporally, spatially and spectrally‐resolved optical techniques, namely the photoluminescence, light induced transient grating, and differential reflectivity were used for investigation of excitation‐dependent PL efficiency, exciton lifetime, and diffusion coefficient in Si‐doped Al‐rich multiple quantum wells and epilayers at various temperatures. Novel features of carrier recombination and in‐plane diffusion were observed. Low‐excitation radiative lifetime of 1–2 ns was found temperature‐independent in 80–150 K interval, while it sublinearly decreased with excitation at excess carrier densities above 1018 cm−3. The lifetime decrease correlated with the increase of diffusion coefficient, indicating excitation‐enhanced delocalization of localized excitons and therefore enhanced capture to nonradiative centers. The droop of photoluminescence efficiency with excitation was the strongest at 80–150 K due to strong delocalisation at low‐temperatures, while at higher temperatures the thermal activation prevailed in photoluminescence excitation dependence. The photoluminescence efficiency quenching at T > 200 K provided rather high activation energies of ∼100 and 160 meV for Al‐rich multiple quantum wells and epilayers, correspondingly.
|