Publications de Nicolas Grandjean

Quantifying carbon site switching dynamics in GaN by electron holography

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté

Off-axis electron holography is utilized to identify point defect reactions and quantify their dynamics by probing the time and temperature dependence of the Fermi level upon annealing. The methodology is illustrated using implanted carbon (C) in GaN, wher ...

2025

Monolayer-Thick GaN/AlN Quantum Well Anodes and Far-UVC Field Emission Device at 226 nm

Jean-François Carlin, Nicolas Grandjean

Far-UVC light sources in the spectral range of200-230 nm effectively kill bacteria and deactivate viruses while being not harmful to health, enabling persistent disinfection of air and surfaces in the presence of humans. So far only excimer lamps have been ...

IEEE2025

Multi-octave bandwidth supercontinuum generation in crystalline Aluminum Nitride-on-sapphire waveguides

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Camille Sophie Brès

Applications such as optical clocks, gas spectroscopy, and optical coherent tomography stand to benefit significantly from the integration of on-chip supercontinuum sources. Materials exhibiting both second- and third-order nonlinearities are particularly ...

International Society for Optical Engineering2025

On the influence of the buffer layer on the optical quality of AlN-on-sapphire epilayers for photonic integrated devices

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Camille Sophie Brès

In the last decade, aluminum nitride (AlN) has proven to be an attractive material for both linear and nonlinear integrated photonics, due to its large transparency window, its low propagation losses and the presence of both second- and third-order nonline ...

SPIE2025

Defects in InGaN QW Structures: Microscopic Properties and Modeling

Nicolas Grandjean

Defects can significantly modify the electrical and optical properties of quantum well (QW) structures based on InGaN. We present an overview of our recent results on the properties of point and extended defects in InGaN/GaN QW devices. By analyzing single ...

SPIE2025

VN-VIn divacancies as the origin of non-radiative recombination centers in InGaN quantum wells

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Yao Chen

In this paper, we investigate the nature of surface defects originating from the high-temperature (HT) GaN buffer and their incorporation into InGaN quantum wells (QWs) grown using the metalorganic vapor phase epitaxy technique. In particular, we conduct a ...

AIP Publishing2025

Two faces of superradiance in tandem-cavity ridge waveguide heterostructures

Nicolas Grandjean

Cooperative emission due to spontaneous build-up and rapid decay of macroscopic polarization in a strongly inverted gain medium is drastically different from the lasing dynamics. The medium polarization and not the cavity field drives the emission from a d ...

SPIE2024

Decoupling Interlayer Spacing and Cation Dipole on Exciton Binding Energy in Layered Halide Perovskites

Rosario Scopelliti, Nicolas Grandjean, Jun Ho Yum, Kevin Sivula, Simon Nussbaum, Han-Hee Cho, Yeonju Kim

Layered halide perovskites (LHPs) are emerging semiconductor materials due to their superior environmental stability compared to that of traditional halide perovskites. While LHPs have tunable optoelectronic properties, quantum and dielectric confinement e ...

2024

AlN-based anodes for far-UVC field emission device at 225 nm

Jean-François Carlin, Nicolas Grandjean

We report on progress in the realization of Field Emission Devices (FED) with AlN-based anodes emitting in the spectral window of 200-230nm for persistent disinfection of air and surfaces in the presence of humans. Modeling, experimental studies, and trade ...

SPIE2024

Identification and thermal healing of focused ion beam-induced defects in GaN using off-axis electron holography

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Yi Wang

Thermal healing of focused ion beam-implanted defects in GaN is investigated by off-axis electron holography in TEM. The data reveal that healing starts at temperatures as low as about 250 degrees C. The healing processes result in an irreversible transiti ...

Iop Publishing Ltd2024

Investigation and modeling of the role of interface defects in the optical degradation of InGaN/GaN LEDs

Jean-François Carlin, Nicolas Grandjean, Camille Haller

We investigate the degradation mechanisms of In0.2Ga0.8N/GaN light emitting diodes through combined experimental analysis and simulations. The devices were submitted to constant current stress at 100 mA. Depending on the measuring current level, two degrad ...

2024

Sub-20 kHz low-frequency noise near ultraviolet butt-coupled fiber Bragg grating external cavity laser diode

Nicolas Grandjean, Raphaël Butté

We present a butt-coupled InGaN fiber Bragg grating (FBG) semiconductor laser diode operating below 400 nm in the single-mode emission regime. This compact coherent laser source exhibits an intrinsic linewidth of 14 kHz in the near-UV range and a side-mode ...

AIP American Institute of Physics2024

GaN Surface Passivation by MoS2 Coating

Jean-François Carlin, Nicolas Grandjean, Mitali Banerjee

In this study, we investigate the impact of two-dimensional MoS2 coating on the optical properties of surface GaN/AlGaN quantum wells (QWs). A strong enhancement in GaN QW light emission is observed with monolayer-MoS2 coating, yielding luminescence intens ...

American Chemical Society (ACS)2024

Origin of giant enhancement of phase contrast in electron holography of modulation-doped n-type GaN

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté

The electron optical phase contrast probed by electron holography at n-n+ GaN doping steps is found to exhibit a giant enhancement, in sharp contrast to the always smaller than expected phase contrast reported for p-n junctions. We unravel the physical ori ...

2024

Investigation of the Impact of Point Defects in InGaN/GaN Quantum Wells with High Dislocation Densities

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Duncan Thomas Lindsay Alexander, Pierre Christophe Lottigier, Thomas Fjord Kjaersgaard Weatherley, Davide Maria Di Paola

In this work, we report on the efficiency of single InGaN/GaN quantum wells (QWs) grown on thin (

MDPI2023

Polariton lasing in AlGaN microring with GaN/AlGaN quantum wells

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté

Microcavity polaritons are strongly interacting hybrid light-matter quasiparticles, which are promising for the development of novel light sources and active photonic devices. Here, we report polariton lasing in the UV spectral range in microring resonator ...

AIP Publishing2023

III-N Optoelectronic Devices: Understanding the Physics of Electro-Optical Degradation

Jean-François Carlin, Nicolas Grandjean, Camille Haller

III-N optoelectronic devices are of great interest for many applications. Visible emitters (based on InGaN) are widely used in the lighting, display and automotive fields. Ultraviolet LEDs (based on AlGaN) are expected to be widely used for disinfection, m ...

SPIE2023

Optical and thermal characterization of a group-III nitride semiconductor membrane by microphotoluminescence spectroscopy and Raman thermometry

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Ian Michael Rousseau

We present the simultaneous optical and thermal analysis of a freestanding photonic semiconductor membrane made from wurtzite III-nitride material. By linking microphotoluminescence spectroscopy with Raman thermometry and other spectroscopic techniques, we ...

Amer Physical Soc2023

Defects in III-N LEDs: experimental identification and impact on electro-optical characteristics

Jean-François Carlin, Nicolas Grandjean, Mauro Mosca, Camille Haller

III-N light-emitting-diodes (LEDs) are subject of intense investigations, thanks to their high efficiency and great reliability. The quality of the semiconductor material has a significant impact on the electro-optical performance of LEDs: for this reason, ...

SPIE-INT SOC OPTICAL ENGINEERING2022

Near ultraviolet photonic integrated lasers based on silicon nitride

Nicolas Grandjean, Rui Ning Wang, Tobias Kippenberg, Camille Haller, Junqiu Liu, Grigorii Likhachev, Andrey Voloshin, Anat Siddharth

Low phase noise lasers based on the combination of III-V semiconductors and silicon photonics are well established in the near-infrared spectral regime. Recent advances in the development of low-loss silicon nitride-based photonic integrated resonators hav ...

AIP Publishing2022