Boron nitride for excitonics, nano photonics, and quantum technologies

Abstract

<jats:title>Abstract</jats:title><jats:p>We review the recent progress regarding the physics and applications of boron nitride bulk crystals and its epitaxial layers in various fields. First, we highlight its importance from optoelectronics side, for simple devices operating in the deep ultraviolet, in view of sanitary applications. Emphasis will be directed towards the unusually strong efficiency of the exciton–phonon coupling in this indirect band gap semiconductor. Second, we shift towards nanophotonics, for the management of hyper-magnification and of medical imaging. Here, advantage is taken of the efficient coupling of the electromagnetic field with some of its phonons, those interacting with light at 12 and 6 µm in vacuum. Third, we present the different defects that are currently studied for their propensity to behave as single photon emitters, in the perspective to help them becoming challengers of the NV centres in diamond or of the double vacancy in silicon carbide in the field of modern and developing quantum technologies.</jats:p>

Band gap measurements of monolayer h-BN and insights into carbon-related point defects

“…[1][2][3] With an optical band gap of about 6 eV, and an indirect-to-direct band gap crossover in the transition from bulk to monolayer, [4][5][6] h-BN shows very bright deep ultraviolet (DUV) emission [7][8][9] and defect mediated emission from the DUV all the way doi:10.1088/2053-1583/ac0d9c to the near-infrared. [10][11][12][13][14] In particular, point defects have been observed to act as singlephoton sources. [15][16][17][18][19][20][21][22][23] Such properties place bulk h-BN and its monolayer form in the spotlight for many potential applications, including DUV light emitting devices, [24][25][26] dielectric layers for two-dimensional (2D) heterostructures [27][28][29] and room temperature (RT) single photon emitters (SPEs) for quantum technologies.…”

Monolayer Boron Nitride: Hyperspectral Imaging in the Deep Ultraviolet

“…hBN is also emerging as an exciting material in its own right, oering novel material properties that enable a broad range of optical, electro-optical and quantum optics functionalities in various spectral domains. 9,10 It is a natural hyperbolic material in the mid-infrared range, it hosts defects that can be engineered to obtain room-temperature, single-photon emission in the ultraviolet, visible and near-infrared ranges, and it exhibits exceptional properties in the deep-ultraviolet (deep-UV) for a new generation of emitters and detectors in the UV-C. 11 Interestingly, in contrast to TMDs, both the ML and the bulk phases have remarkable optoelectronic properties in the case of hBN, particularly regarding the intense emission of bulk hBN despite the indirect nature of its bandgap. 9 As for the rst demonstration of a direct bandgap in ML MoS 2 , 3,4 optical spectroscopy in 2D materials largely relies on microscopy in samples fabricated by exfoliation of bulk lamellar crystals.…”

Hexagonal boron nitride: optical properties in the deep ultraviolet

“…Thanks to its ultrawide bandgap of ∼6 eV, hBN is a 2D material where the optical response exhibits intrinsic and extrinsic signatures speading over several eVs. Free exciton recombination occurs above ∼5.7 eV (below ∼215 nm), extended defects and shallow levels contribute to the emission between ∼5 and 5.7 eV (wavelength between ∼215 and 250 nm) and deep levels provide potential single photon sources in the near-UV (4.1 eV) and the visible (2-3 eV) spectral domains [6,7] and also in the near-IR one, as recently demonstrated [8]. Such a spectral decoupling of the various contributions to the optical response allows to separately study the diverse phenomena underlying the rich physics in hBN.…”

“…hBN is also emerging as an exciting material in its own right, offering novel material properties that enable a broad range of optical, electro-optical and quantum optics functionalities [6,7]. The outstanding photonic properties of hBN span very different spectral domains.…”