Ultrawide-bandgap semiconductors for deep-UV optoelectronics
We explore the physics of ultrawide-bandgap semiconductors for applications in deep-ultraviolet optoelectronics. Our activities are currently focused on hexagonal boron nitride, a 2D material with outstanding properties for deep-ultraviolet devices
Guillaume CASSABOIS, Bernard GIL & Pierre VALVIN
For more than seven decades, hexagonal boron nitride (hBN) has been employed as an inert, thermally stable engineering ceramic. The growth of high-quality hBN crystals in 2004 renewed interest in hBN. Recent research has revealed that this 2D material exhibits a unique combination of optical properties from the mid-infrared to the deep-ultraviolet that enable novel photonic functionalities.
Our activities are focused on the physics of hBN for deep-ultraviolet optoelectronics. Our pioneering contributions to the understanding of hBN optoelectronic properties have shown that hBN combines the best of the properties normally associated only with indirect or direct bandgap semiconductors. Since bulk hBN has an indirect bandgap, light extraction efficiency is high because of the low reabsorption at the emission wavelength. Strikingly, bulk hBN has also a high internal quantum efficiency, close to values typical of direct bandgap semiconductors,
because the strong electron-phonon coupling in hBN makes phonon-assisted recombination fast enough to bypass nonradiative relaxation.
The next step is to reach these outstanding performances in thin layers grown by the scalable growth approach of epitaxy, and to achieve their doping for electrical injection. In parallel, the study of few-layer hBN samples in the context of twistronics is expected to produce novel exotic electronic properties. These projects are developed by means of state-of-the-art setups for deep-ultraviolet spectroscopy allowing reflectivity, cw and time resolved macro photoluminescence, and spatially-resolved micro-photoluminescence experiments.
Honeycomb lattice of hBN
SOME RECENT PUBLICATIONS
Exciton and Phonon Radiative Linewidths in Monolayer Boron Nitride
G. Cassabois, G. Fugallo, C. Elias, P. Valvin, A. Rousseau, B. Gil, A. Summerfield, C. J. Mellor, T. S. Cheng, L. Eaves, C. T. Foxon, P. H. Beton, M. Lazzeri, A. Segura, and S. V. Novikov
Bernal Boron Nitride Crystals Identified by Deep-Ultraviolet Cryomicroscopy
A. Rousseau, P. Valvin, W. Desrat, L. Xue, J. Li, J. H. Edgar, G. Cassabois and B. Gil
Monolayer Boron Nitride: Hyperspectral Imaging in the Deep Ultraviolet
A. Rousseau, L. Ren, A. Durand, P. Valvin, B. Gil, K. Watanabe, T. Taniguchi, B. Urbaszek, X. Marie, C. Robert and G. Cassabois
Flat Bands and Giant Light-Matter Interaction in Hexagonal Boron Nitride
C. Elias, G. Fugallo, P. Valvin, C. L’Henoret, J. Li, J. H. Edgar, F. Sottile, M. Lazzeri, A. Ouerghi, B. Gil, and G. Cassabois
Determination of the optical bandgap of the Bernal and rhombohedral boron nitride polymorphs
A. Rousseau, M. Moret, P. Valvin, W. Desrat, J. Li, E. Janzen, L. Xue, J. H. Edgar, G. Cassabois and B. Gil
Shallow and deep levels in carbon-doped hexagonal boron nitride crystals
T. Pelini, C. Elias, R. Page, L. Xue, S. Liu, J. Li, J. H. Edgar, A. Dréau, V. Jacques, P. Valvin, B. Gil, and G. Cassabois
Photonics with hexagonal boron nitride
J. D. Caldwell, I. Aharonovich, G. Cassabois, J. H. Edgar, B. Gil and D. N. Basov